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KSH(1)									KSH(1)

NAME
       ksh,  rksh,  pfksh  - KornShell, a standard/restricted command and pro‐
       gramming language

SYNOPSIS
       ksh [ ±abcefhikmnoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ -  ]  [
       arg ... ]
       rksh  [ ±abcefhikmnoprstuvxBCD ] [ -R file ] [ ±o option ] ...  [ - ] [
       arg ... ]

DESCRIPTION
       Ksh is a command and programming language that executes	commands  read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter ksh; it is used to set up login names and  execution	 envi‐
       ronments whose capabilities are more controlled than those of the stan‐
       dard shell.  Rpfksh is a profile shell version of  the  command	inter‐
       preter ksh; it is used to to execute commands with the attributes spec‐
       ified by the user's profiles (see pfexec(1)).  See Invocation below for
       the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

	      ;	  &   (	  )   ⎪	  <   >	  new-line   space   tab

       A  blank	 is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or	 underscore.   Identi‐
       fiers  are used as components of variable names.	 A vname is a sequence
       of one or more identifiers separated by a . and optionally preceded  by
       a  ..   Vnames  are  used  as function and variable names.  A word is a
       sequence of characters from the character set defined  by  the  current
       locale, excluding non-quoted metacharacters.

       A  command  is a sequence of characters in the syntax of the shell lan‐
       guage.  The shell reads each command and carries out the desired action
       either  directly or by invoking separate utilities.  A built-in command
       is a command that is carried out by the shell itself without creating a
       separate	 process.   Some  commands are built-in purely for convenience
       and are not documented here.  Built-ins that cause side effects in  the
       shell environment and built-ins that are found before performing a path
       search (see Execution below) are documented here.  For historical  rea‐
       sons,  some  of these built-ins behave differently than other built-ins
       and are called special built-ins.

   Commands.
       A simple-command is  a  list  of	 variable  assignments	(see  Variable
       Assignments  below) or a sequence of blank separated words which may be
       preceded by a list of variable  assignments  (see  Environment  below).
       The  first  word	 specifies  the	 name  of  the command to be executed.
       Except as specified below, the remaining words are passed as  arguments
       to  the invoked command.	 The command name is passed as argument 0 (see
       exec(2)).  The value of a simple-command is its exit status;  0-255  if
       it  terminates  normally;  256+signum  if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by ⎪.  The
       standard output of each command but the last is connected by a  pipe(2)
       to the standard input of the next command.  Each command, except possi‐
       bly the last, is run as a separate process; the	shell  waits  for  the
       last  command  to terminate.  The exit status of a pipeline is the exit
       status of the last command unless the pipefail option is enabled.  Each
       pipeline	 can be preceded by the reserved word !	 which causes the exit
       status of the pipeline to become 0 if the exit status of the last  com‐
       mand is non-zero, and 1 if the exit status of the last command is 0.

       A  list	is  a sequence of one or more pipelines separated by ;, &, ⎪&,
       &&, or ⎪⎪, and optionally terminated by ;, &, or	 ⎪&.   Of  these  five
       symbols,	 ;,  &, and ⎪& have equal precedence, which is lower than that
       of && and ⎪⎪.  The symbols && and ⎪⎪ also  have	equal  precedence.   A
       semicolon (;) causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the  preceding  pipeline
       (i.e.,  the shell does not wait for that pipeline to finish).  The sym‐
       bol ⎪& causes asynchronous execution of the preceding pipeline  with  a
       two-way	pipe  established  to the parent shell; the standard input and
       output of the spawned pipeline can be written to and read from  by  the
       parent shell by applying the redirection operators <& and >& with arg p
       to commands and by using -p option of the built-in  commands  read  and
       print described later.  The symbol && (⎪⎪) causes the list following it
       to be executed only if the preceding pipeline returns a zero (non-zero)
       value.	One  or more new-lines may appear in a list instead of a semi‐
       colon, to delimit a command.  The first item  of the first pipeline  of
       a  list	that is a simple command not beginning with a redirection, and
       not occurring within a while, until, or if list, can be preceded	 by  a
       semicolon.   This  semicolon  is	 ignored  unless  the showme option is
       enabled as described with the set built-in below.

       A command is either a simple-command or one of the  following.	Unless
       otherwise  stated,  the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
	      Each time a for command is executed, vname is set	 to  the  next
	      word  taken  from the in word list.  If in word ...  is omitted,
	      then the for command executes the do list once  for  each	 posi‐
	      tional  parameter	 that  is  set	starting from 1 (see Parameter
	      Expansion below).	 Execution ends when there are no  more	 words
	      in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
	      The  arithmetic  expression expr1 is evaluated first (see Arith‐
	      metic evaluation below).	The  arithmetic	 expression  expr2  is
	      repeatedly  evaluated  until  it evaluates to zero and when non-
	      zero, list is executed and the arithmetic expression expr3 eval‐
	      uated.   If  any expression is omitted, then it behaves as if it
	      evaluated to 1.

       select vname [ in word ... ] ;do list ;done
	      A select command prints on standard error	 (file	descriptor  2)
	      the set of words, each preceded by a number.  If in word ...  is
	      omitted, then the positional parameters starting from 1 are used
	      instead  (see  Parameter	Expansion  below).   The PS3 prompt is
	      printed and a line is read from the  standard  input.   If  this
	      line consists of the number of one of the listed words, then the
	      value of the variable vname is set to the word corresponding  to
	      this  number.   If  this	line  is  empty, the selection list is
	      printed again.  Otherwise the value of the variable vname is set
	      to  null.	  The contents of the line read from standard input is
	      saved in the variable REPLY.  The	 list  is  executed  for  each
	      selection	 until	a break or end-of-file is encountered.	If the
	      REPLY variable is set to null by the execution of list, then the
	      selection	 list  is printed before displaying the PS3 prompt for
	      the next selection.

       case word in [ [(]pattern [ ⎪ pattern ] ... ) list ;; ] ... esac
	      A case command executes the list associated with the first  pat‐
	      tern that matches word.  The form of the patterns is the same as
	      that used for file-name generation  (see	File  Name  Generation
	      below).	The ;; operator causes execution of case to terminate.
	      If ;& is used in place of ;; the next subsequent list,  if  any,
	      is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
	      The list following if is executed and, if it returns a zero exit
	      status, the list following the first then is  executed.	Other‐
	      wise,  the  list following elif is executed and, if its value is
	      zero, the list following the next	 then  is  executed.   Failing
	      each successive elif list, the else list is executed.  If the if
	      list has non-zero exit status and there is no  else  list,  then
	      the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
	      A	 while	command repeatedly executes the while list and, if the
	      exit status of the last command in the list  is  zero,  executes
	      the  do  list; otherwise the loop terminates.  If no commands in
	      the do list are executed, then the while command returns a  zero
	      exit  status;  until may be used in place of while to negate the
	      loop termination test.

       ((expression))
	      The expression is evaluated using the rules for arithmetic eval‐
	      uation  described below.	If the value of the arithmetic expres‐
	      sion is non-zero, the exit status is 0, otherwise the exit  sta‐
	      tus is 1.

       (list)
	      Execute list in a separate environment.  Note, that if two adja‐
	      cent open parentheses are needed for nesting, a  space  must  be
	      inserted	to  avoid  evaluation  as  an  arithmetic  command  as
	      described above.

       { list;}
	      list is simply executed.	Note that unlike the metacharacters  (
	      and  ),  { and } are reserved words and must occur at the begin‐
	      ning of a line or after a ; in order to be recognized.

       [[ expression ]]
	      Evaluates expression and returns a zero exit status when expres‐
	      sion is true.  See Conditional Expressions below, for a descrip‐
	      tion of expression.

       function varname { list ;}
       varname () { list ;}
	      Define a function which is referenced by	varname.   A  function
	      whose  varname contains a .  is called a discipline function and
	      the portion of the varname preceding the last .  must  refer  to
	      an  existing  variable.  The body of the function is the list of
	      commands between { and }.	 A function defined with the  function
	      varname syntax can also be used as an argument to the .  special
	      built-in command to get the equivalent behavior as if  the  var‐
	      name() syntax were used to define it.  (See Functions below.)

       namespace identifier { list ;}
	      Defines  or uses the name space identifier and runs the commands
	      in list in this name space.  (See Name Spaces below.)

       & [ name [ arg... ]  ]
	      Causes subsequent list commands terminated by & to be placed  in
	      the  background  job  pool  name.	  If name is omitted a default
	      unnamed pool is used.  Commands in a named background  pool  may
	      be executed remotely.

       time [ pipeline ]
	      If  pipeline is omitted the user and system time for the current
	      shell and completed  child  processes  is	 printed  on  standard
	      error.   Otherwise, pipeline is executed and the elapsed time as
	      well as the user and system time are printed on standard	error.
	      The TIMEFORMAT variable may be set to a format string that spec‐
	      ifies how the timing information should be displayed.  See Shell
	      Variables below for a description of the TIMEFORMAT variable.

       The  following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do  done	{  }  function
       select time [[ ]] !

   Variable Assignments.
       One  or	more variable assignments can start a simple command or can be
       arguments to the typeset, enum, export, or  readonly  special  built-in
       commands	 as  well  as  to other declaration commands created as types.
       The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
	      No space is permitted between varname and the = or between = and
	      word.

       varname=(assign_list)
	      No  space	 is permitted between varname and the =.  The variable
	      varname is unset before the assignment.  An assign_list  can  be
	      one of the following:
		      word ...
			     Indexed array assignment.
		      [word]=word ...
			     Associative  array	 assignment.   If  preceded by
			     typeset -a this  will  create  an	indexed	 array
			     instead.
		      assignment ...
			     Compound  variable	 assignment.   This  creates a
			     compound variable varname with  sub-variables  of
			     the  form	varname.name,  where  name is the name
			     portion of assignment.  The value of varname will
			     contain  all the assignment elements.  Additional
			     assignments made to sub-variables of varname will
			     also  be  displayed  as part of the value of var‐
			     name.  If no assignments are  specified,  varname
			     will  be a compound variable allowing subsequence
			     child elements to be defined.
		      typeset [options] assignment ...
			     Nested variable assignment.  Multiple assignments
			     can  be specified by separating each of them with
			     a ;.  The previous	 value	is  unset  before  the
			     assignment.   Other  declaration commands such as
			     readonly, enum, and  other	 declaration  commands
			     can be used in place of typeset.
		      . filename
			     Include  the  assignment  commands	 contained  in
			     filename.

       In addition, a += can be used in place of the = to signify adding to or
       appending  to  the previous value.  When += is applied to an arithmetic
       type, word is evaluated as an arithmetic expression and	added  to  the
       current value.  When applied to a string variable, the value defined by
       word is appended to the value.  For compound assignments, the  previous
       value  is not unset and the new values are appended to the current ones
       provided that the types are compatible.

       The right hand side of a variable assignment undergoes all  the	expan‐
       sion listed below except word splitting, brace expansion, and file name
       generation.  When the left hand side is an  assignment  is  a  compound
       variable	 and  the  right  hand is the name of a compound variable, the
       compound variable on the right will be copied or appended to  the  com‐
       pound variable on the left.

   Comments.
       A  word beginning with # causes that word and all the following charac‐
       ters up to a new-line to be ignored.
   Aliasing.
       The first word of each command is replaced by the text of an  alias  if
       an alias for this word has been defined.	 An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion  characters,  parameter  expansion  and  command substitution
       characters, the characters / and =.  The replacement string can contain
       any  valid shell script including the metacharacters listed above.  The
       first word of each command in the replaced text, other  than  any  that
       are  in	the process of being replaced, will be tested for aliases.  If
       the last character of the alias value is a blank then the word  follow‐
       ing the alias will also be checked for alias substitution.  Aliases can
       be used to redefine built-in commands but cannot be  used  to  redefine
       the  reserved  words  listed  above.  Aliases can be created and listed
       with the alias command and can be removed with the unalias command.
       Aliasing is performed when scripts are read, not while  they  are  exe‐
       cuted.	Therefore,  for	 an alias to take effect, the alias definition
       command has to be executed before  the  command	which  references  the
       alias is read.
       The  following  aliases are compiled into the shell but can be unset or
       redefined:
			   autoload=′typeset -fu′
			   command=′command  ′
			   compound=′typeset -C′
			   fc=hist
			   float=′typeset -lE′
			   functions=′typeset -f′
			   hash=′alias -t --′
			   history=′hist -l′
			   integer=′typeset -li′
			   nameref=′typeset -n′
			   nohup=′nohup	 ′
			   r=′hist -s′
			   redirect=′command exec′
			   source=′command .′
			   stop=′kill -s STOP′
			   suspend=′kill -s STOP $$′
			   times=′{ { time;} 2>&1;}′
			   type=′whence -v′

   Tilde Substitution.
       After alias substitution is performed, each word is checked to  see  if
       it begins with an unquoted ∼.  For tilde substitution, word also refers
       to the word portion of parameter	 expansion  (see  Parameter  Expansion
       below).	 If  it	 does, then the word up to a / is checked to see if it
       matches a user name in the password database (See getpwname(3).)	 If  a
       match  is  found,  the ∼ and the matched login name are replaced by the
       login directory of the matched user.  If no match is found, the	origi‐
       nal  text  is  left  unchanged.	 A ∼ by itself, or in front of a /, is
       replaced by $HOME.  A ∼ followed by a + or - is replaced by  the	 value
       of $PWD and $OLDPWD respectively.

       In  addition,  when expanding a variable assignment, tilde substitution
       is attempted when the value of the assignment begins with a ∼, and when
       a ∼ appears after a :.  The : also terminates a ∼ login name.

   Command Substitution.
       The  standard  output  from a command list enclosed in parentheses pre‐
       ceded by a dollar sign ( $(list) ), or in a brace group preceded	 by  a
       dollar  sign  (	${ list;} ), or in a pair of grave accents (``) may be
       used as part or all of a word; trailing new-lines are removed.  In  the
       second case, the { and } are treated as a reserved words so that { must
       be followed by a blank and } must appear at the beginning of  the  line
       or  follow  a  ;.  In the third (obsolete) form, the string between the
       quotes is processed for special quoting characters before  the  command
       is  executed (see Quoting below).  The command substitution $(cat file)
       can be replaced by the equivalent but  faster  $(<file).	  The  command
       substitution  $(n<#)  will  expand  to the current byte offset for file
       descriptor n.  Except for the second form, the command list is run in a
       subshell	 so  that  no side effects are possible.  For the second form,
       the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded	 by  a
       dollar  sign  (	$(())  )  is  replaced	by the value of the arithmetic
       expression within the double parentheses.

   Process Substitution.
       Each command argument of the form <(list) or >(list) will  run  process
       list asynchronously connected to some file in /dev/fd if this directory
       exists, or else a fifo a temporary directory.  The name	of  this  file
       will  become  the  argument  to	the  command.	If  the form with > is
       selected then writing on this file will provide input for list.	 If  <
       is used, then the file passed as an argument will contain the output of
       the list process.  For example,

	      paste <(cut -f1  file1)  <(cut  -f3  file2)  |  tee  >(process1)
	      >(process2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and  sends	 it  to	 the  processes	 process1  and
       process2,  as  well  as putting it onto the standard output.  Note that
       the file, which is passed as an argument to  the	 command,  is  a  UNIX
       pipe(2) so programs that expect to lseek(2) on the file will not work.

       Process	substitution  of  the form <(list) can also be used with the <
       redirection operator which causes the output of	list  to  be  standard
       input or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       ∗, @, #, ?, -, $, and !.	 A variable is denoted by a vname.  To	create
       a variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already  exist.   A  variable	has  a
       value  and  zero	 or more attributes.  Variables can be assigned values
       and attributes by using the  typeset  special  built-in	command.   The
       attributes  supported by the shell are described later with the typeset
       special	built-in  command.   Exported  variables   pass	  values   and
       attributes to the environment.

       The  shell supports both indexed and associative arrays.	 An element of
       an array variable is referenced by a subscript.	 A  subscript  for  an
       indexed	array  is  denoted by an arithmetic expression (see Arithmetic
       evaluation below) between a [ and a ].  To assign values to an  indexed
       array, use vname=(value ...) or set -A vname  value ... .  The value of
       all  non-negative  subscripts  must  be	in  the	 range	of  0  through
       4,194,303.  A negative subscript is treated as an offset from the maxi‐
       mum current index +1 so that -1 refers to the  last  element.   Indexed
       arrays  can  be declared with the -a option to typeset.	Indexed arrays
       need not be declared.  Any reference to a variable with	a  valid  sub‐
       script is legal and an array will be created if necessary.

       An  associative array is created with the -A option to typeset.	A sub‐
       script for an associative array is denoted by a string enclosed between
       [ and ].

       Referencing  any array without a subscript is equivalent to referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

	      vname=value [ vname=value ] ...

       or
	      vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       Attributes assigned by the typeset special built-in  command  apply  to
       all  elements of the array.  An array element can be a simple variable,
       a compound variable or an array variable.  An  element  of  an  indexed
       array  can be either an indexed array or an associative array.  An ele‐
       ment of an associative array can also be either.	 To refer to an	 array
       element	that is part of an array element, concatenate the subscript in
       brackets.  For example, to refer to the foobar element of  an  associa‐
       tive  array  that is defined as the third element of the indexed array,
       use ${vname[3][foobar]}
       A nameref is a variable that is a reference  to	another	 variable.   A
       nameref	is created with the -n attribute of typeset.  The value of the
       variable at the time of the typeset command becomes the	variable  that
       will  be referenced whenever the nameref variable is used.  The name of
       a nameref cannot contain a ..  When a variable or  function  name  con‐
       tains  a	 .,  and the portion of the name up to the first . matches the
       name of a nameref, the variable referred to is  obtained	 by  replacing
       the  nameref  portion  with  the name of the variable referenced by the
       nameref.	 If a nameref is used as the index of a for loop, a name  ref‐
       erence  is established for each item in the list.  A nameref provides a
       convenient way to refer to the variable inside a function whose name is
       passed  as  an  argument	 to a function.	 For example, if the name of a
       variable is passed as the first argument to a function, the command
	      typeset -n var=$1
       inside the function causes references and assignments to var to be ref‐
       erences	and  assignments to the variable whose name has been passed to
       the function.
       If any of the floating point attributes, -E, -F, or -X, or the  integer
       attribute,  -i,	is  set for vname, then the value is subject to arith‐
       metic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be  assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
	      The shell reads all the characters from ${ to the matching }  as
	      part  of the same word even if it contains braces or metacharac‐
	      ters.  The value, if any, of the parameter is substituted.   The
	      braces  are  required  when  parameter  is followed by a letter,
	      digit, or underscore that is not to be interpreted  as  part  of
	      its  name,  when the variable name contains a ..	The braces are
	      also required when a variable is subscripted unless it  is  part
	      of  an  Arithmetic  Expression  or a Conditional Expression.  If
	      parameter is one or more digits then it is a positional  parame‐
	      ter.   A	positional  parameter  of  more than one digit must be
	      enclosed in braces.  If parameter is ∗ or @, then all the	 posi‐
	      tional  parameters, starting with $1, are substituted (separated
	      by a field separator character).	If an array  vname  with  last
	      subscript	 ∗  @,	or for index arrays of the form sub1 ..	 sub2.
	      is used, then the value for each of the  elements	 between  sub1
	      and sub2 inclusive (or all elements for ∗ and @) is substituted,
	      separated by the first character of the value of IFS.
       ${#parameter}
	      If parameter is ∗ or @, the number of positional	parameters  is
	      substituted.   Otherwise, the length of the value of the parame‐
	      ter is substituted.
       ${#vname[*]}
       ${#vname[@]}
	      The number of elements in the array vname is substituted.

       ${@vname}
	      Expands to  the  type  name  (See	 Type  Variables    below)  or
	      attributes of the variable referred to by vname.
       ${!vname}
	      Expands  to the name of the variable referred to by vname.  This
	      will be vname except when vname is a name reference.
       ${!vname[subscript]}
	      Expands to name of the subscript unless subscript is *,  @.   or
	      of  the  form  sub1  ..  sub2.  When subscript is *, the list of
	      array subscripts for vname is generated.	For a variable that is
	      not  an array, the value is 0 if the variable is set.  Otherwise
	      it is null.  When subscript is @, same  as  above,  except  that
	      when  used in double quotes, each array subscript yields a sepa‐
	      rate argument.  When subscript is of the form sub1 ..   sub2  it
	      expands  to  the list of subscripts between sub1 and sub2 inclu‐
	      sive using the same quoting rules as @.
       ${!prefix*}
	      Expands to the names of the variables  whose  names  begin  with
	      prefix.
       ${parameter:-word}
	      If  parameter  is set and is non-null then substitute its value;
	      otherwise substitute word.
       ${parameter:=word}
	      If parameter is not set or is null then  set  it	to  word;  the
	      value  of the parameter is then substituted.  Positional parame‐
	      ters may not be assigned to in this way.
       ${parameter:?word}
	      If parameter is set and is non-null then substitute  its	value;
	      otherwise,  print	 word and exit from the shell (if not interac‐
	      tive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
	      If parameter is set and is non-null then substitute word; other‐
	      wise substitute nothing.
       In the above, word is not evaluated unless it is to be used as the sub‐
       stituted string, so that, in the following  example,  pwd  is  executed
       only if d is not set or is null:
	      print ${d:-$(pwd)}
       If  the	colon  (  :  ) is omitted from the above expressions, then the
       shell only checks whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
	      Expands to the portion of the value of parameter starting at the
	      character (counting from 0) determined by expanding offset as an
	      arithmetic expression and consisting of the number of characters
	      determined  by  the arithmetic expression defined by length.  In
	      the second form, the remainder of the value is used.  If A nega‐
	      tive  offset  counts  backwards from the end of parameter.  Note
	      that one or more blanks is required in front of a minus sign  to
	      prevent  the  shell  from	 interpreting  the operator as :-.  If
	      parameter is ∗ or @, or is an array name indexed by ∗ or @, then
	      offset  and  length  refer to the array index and number of ele‐
	      ments respectively.  A negative offset is taken relative to  one
	      greater  than  the  highest  subscript  for indexed arrays.  The
	      order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
	      If the shell pattern matches  the	 beginning  of	the  value  of
	      parameter,  then the value of this expansion is the value of the
	      parameter with the matched portion deleted; otherwise the	 value
	      of  this parameter is substituted.  In the first form the small‐
	      est matching pattern is deleted  and  in	the  second  form  the
	      largest matching pattern is deleted.  When parameter is @, *, or
	      an array variable with subscript @ or *, the substring operation
	      is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
	      If  the shell pattern matches the end of the value of parameter,
	      then the value of this expansion is the value of	the  parameter
	      with the matched part deleted; otherwise substitute the value of
	      parameter.  In the first form the smallest matching  pattern  is
	      deleted  and  in the second form the largest matching pattern is
	      deleted.	When parameter is @, *, or an array variable with sub‐
	      script  @	 or *, the substring operation is applied to each ele‐
	      ment in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
	      Expands parameter and replaces the longest match of pattern with
	      the  given  string.  Each occurrence of \n in string is replaced
	      by the portion of parameter that matches the  n-th  sub-pattern.
	      In  the  first  form,  only  the	first occurrence of pattern is
	      replaced.	 In  the  second  form,	 each  match  for  pattern  is
	      replaced by the given string.  The third form restricts the pat‐
	      tern match to the beginning of the string while the fourth  form
	      restricts	 the  pattern  match  to  the end of the string.  When
	      string is null, the pattern will be deleted and the /  in	 front
	      of  string  may be omitted.  When parameter is @, *, or an array
	      variable with subscript @ or *, the  substitution	 operation  is
	      applied  to each element in turn.	 In this case, the string por‐
	      tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
	      #	     The number of positional parameters in decimal.
	      -	     Options supplied to the shell on invocation or by the set
		     command.
	      ?	     The decimal value returned by the last executed command.
	      $	     The process number of this shell.
	      _	     Initially,	 the value of _ is an absolute pathname of the
		     shell or script being executed as passed in the  environ‐
		     ment.   Subsequently  it is assigned the last argument of
		     the previous command.  This parameter is not set for com‐
		     mands  which  are	asynchronous.	This parameter is also
		     used to hold the name of  the  matching  MAIL  file  when
		     checking for mail.	 While defining a compound variable or
		     a type, _ is initialized as a reference to	 the  compound
		     variable or type.	When a discipline function is invoked,
		     _ is initialized as a reference to the  variable  associ‐
		     ated  with	 the call to this function.  Finally when _ is
		     used as the name of the first variable of a type  defini‐
		     tion,  the new type is derived from the type of the first
		     variable (See Type Variables  below.).
	      !	     The process id or the pool name and  job  number  of  the
		     last  background  command	invoked or the most recent job
		     put in the	 background  with  the	bg  built-in  command.
		     Background	 jobs  started	in a named pool will be in the
		     form pool.number where pool is the pool name  and	number
		     is the job number within that pool.
	      .sh.command
		     When  processing a DEBUG trap, this variable contains the
		     current command line that is about to run.
	      .sh.edchar
		     This variable contains the value of the keyboard  charac‐
		     ter  (or sequence of characters if the first character is
		     an ESC, ascii 033) that has been entered when  processing
		     a	KEYBD  trap (see Key Bindings below).  If the value is
		     changed as part of the trap action, then  the  new	 value
		     replaces the key (or key sequence) that caused the trap.
	      .sh.edcol
		     The  character  position of the cursor at the time of the
		     most recent KEYBD trap.
	      .sh.edmode
		     The value is set to ESC  when  processing	a  KEYBD  trap
		     while  in	vi insert mode.	 (See Vi Editing Mode  below.)
		     Otherwise, .sh.edmode is null  when  processing  a	 KEYBD
		     trap.
	      .sh.edtext
		     The  characters  in  the  input buffer at the time of the
		     most recent KEYBD trap.  The value is null when not  pro‐
		     cessing a KEYBD trap.
	      .sh.file
		     The  pathname  of the file than contains the current com‐
		     mand.
	      .sh.fun
		     The name of the current function that is being executed.
	      .sh.level
		     Set to the current function depth.	 This can  be  changed
		     inside a DEBUG trap and will set the context to the spec‐
		     ified level.
	      .sh.lineno
		     Set during a DEBUG trap to the line number for the caller
		     of each function.
	      .sh.match
		     An	 indexed  array which stores the most recent match and
		     sub-pattern matches  after	 conditional  pattern  matches
		     that match and after variables expansions using the oper‐
		     ators #, %, or /.	The 0-th element stores	 the  complete
		     match  and	 the  i-th.  element stores the i-th submatch.
		     The .sh.match variable becomes unset  when	 the  variable
		     that has expanded is assigned a new value.
	      .sh.math
		     Used  for	defining  arithmetic functions (see Arithmetic
		     evaluation below).	 and stores the list of	 user  defined
		     arithmetic functions.
	      .sh.name
		     Set to the name of the variable at the time that a disci‐
		     pline function is invoked.
	      .sh.subscript
		     Set to the name subscript of the  variable	 at  the  time
		     that a discipline function is invoked.
	      .sh.subshell
		     The current depth for subshells and command substitution.
	      .sh.value
		     Set to the value of the variable at the time that the set
		     or append discipline function is invoked.	 When  a  user
		     defined  arithmetic  function  is	invoked,  the value of
		     .sh.value is saved and .sh.value is set  to  long	double
		     precision floating point.	.sh.value is restored when the
		     function returns.
	      .sh.version
		     Set to a value that identifies the version of this shell.
	      KSH_VERSION
		     A name reference to .sh.version.
	      LINENO The current line number within  the  script  or  function
		     being executed.
	      OLDPWD The previous working directory set by the cd command.
	      OPTARG The  value	 of  the last option argument processed by the
		     getopts built-in command.
	      OPTIND The index of the last option argument  processed  by  the
		     getopts built-in command.
	      PPID   The process number of the parent of the shell.
	      PWD    The present working directory set by the cd command.
	      RANDOM Each  time this variable is referenced, a random integer,
		     uniformly distributed between 0 and 32767, is  generated.
		     The  sequence  of	random	numbers	 can be initialized by
		     assigning a numeric value to RANDOM.
	      REPLY  This variable is set by the select statement and  by  the
		     read built-in command when no arguments are supplied.
	      SECONDS
		     Each time this variable is referenced, the number of sec‐
		     onds since shell invocation is returned.  If  this	 vari‐
		     able  is  assigned	 a value, then the value returned upon
		     reference will be the value that was  assigned  plus  the
		     number of seconds since the assignment.
	      SHLVL  An	 integer  variable  the	 is  incremented each time the
		     shell is invoked and is exported.	If SHLVL is not in the
		     environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
	      CDPATH The search path for the cd command.
	      COLUMNS
		     If	 this variable is set, the value is used to define the
		     width of the edit window for the shell edit modes and for
		     printing select lists.
	      EDITOR If	 the  VISUAL  variable	is  not set, the value of this
		     variable will be checked for the  patterns	 as  described
		     with  VISUAL  below  and the corresponding editing option
		     (see Special Command set below) will be turned on.
	      ENV    If this variable is set, then parameter  expansion,  com‐
		     mand  substitution,  and arithmetic substitution are per‐
		     formed on the value  to  generate	the  pathname  of  the
		     script  that  will	 be executed when the shell is invoked
		     interactively (see Invocation below).  This file is typi‐
		     cally  used  for  alias  and  function  definitions.  The
		     default value is $HOME/.kshrc.  On systems that support a
		     system  wide   /etc/ksh.kshrc initialization file, if the
		     filename generated by the expansion of  ENV  begins  with
		     /./  or ././ the system wide initialization file will not
		     be executed.
	      FCEDIT Obsolete name for the default editor name	for  the  hist
		     command.  FCEDIT is not used when HISTEDIT is set.
	      FIGNORE
		     A	pattern that defines the set of filenames that will be
		     ignored when performing filename matching.
	      FPATH  The search path for function definitions.	 The  directo‐
		     ries  in  this path are searched for a file with the same
		     name as the function or command when a function with  the
		     -u	 attribute  is	referenced  and	 when a command is not
		     found.  If an executable file with the name of that  com‐
		     mand  is  found, then it is read and executed in the cur‐
		     rent environment.	Unlike	PATH,  the  current  directory
		     must be represented explicitly by .  rather than by adja‐
		     cent : characters or a beginning or ending :.
	      HISTCMD
		     Number of the current command in the history file.
	      HISTEDIT
		     Name for the default editor name for the hist command.
	      HISTFILE
		     If this variable is set when the shell is	invoked,  then
		     the  value	 is the pathname of the file that will be used
		     to	 store	the  command  history  (see  Command  Re-entry
		     below).
	      HISTSIZE
		     If	 this  variable is set when the shell is invoked, then
		     the number of previously entered commands that are acces‐
		     sible by this shell will be greater than or equal to this
		     number.  The default is 512.
	      HOME   The default argument (home directory) for the cd command.
	      IFS    Internal field separators, normally space, tab, and  new-
		     line  that	 are  used  to separate the results of command
		     substitution  or  parameter  expansion  and  to  separate
		     fields with the built-in command read.  The first charac‐
		     ter of the IFS variable is used to separate arguments for
		     the  "$∗"	substitution (see Quoting below).  Each single
		     occurrence of an IFS character in the string to be split,
		     that is not in the isspace character class, and any adja‐
		     cent characters in IFS that are in the isspace  character
		     class,  delimit  a	 field.	 One or more characters in IFS
		     that belong to the isspace	 character  class,  delimit  a
		     field.   In  addition,  if	 the  same  isspace  character
		     appears  consecutively  inside  IFS,  this	 character  is
		     treated  as  if it were not in the isspace class, so that
		     if IFS consists of two tab characters, then two  adjacent
		     tab characters delimit a null field.
	      JOBMAX This  variable  defines  the maximum number running back‐
		     ground jobs that can run at a time.  When this  limit  is
		     reached, the shell will wait for a job to complete before
		     staring a new job.
	      LANG   This variable determines the locale category for any cat‐
		     egory  not specifically selected with a variable starting
		     with LC_ or LANG.
	      LC_ALL This variable overrides the value of  the	LANG  variable
		     and any other LC_ variable.
	      LC_COLLATE
		     This  variable determines the locale category for charac‐
		     ter collation information.
	      LC_CTYPE
		     This variable determines the locale category for  charac‐
		     ter  handling  functions.	 It  determines	 the character
		     classes for pattern matching (see	File  Name  Generation
		     below).
	      LC_NUMERIC
		     This variable determines the locale category for the dec‐
		     imal point character.
	      LINES  If this variable is set, the value is used	 to  determine
		     the  column  length  for  printing	 select lists.	Select
		     lists will print vertically  until	 about	two-thirds  of
		     LINES lines are filled.
	      MAIL   If	 this  variable	 is set to the name of a mail file and
		     the MAILPATH variable is not set, then the shell  informs
		     the user of arrival of mail in the specified file.
	      MAILCHECK
		     This  variable specifies how often (in seconds) the shell
		     will check for changes in the modification time of any of
		     the  files	 specified  by the MAILPATH or MAIL variables.
		     The default value is 600  seconds.	  When	the  time  has
		     elapsed  the  shell  will	check  before issuing the next
		     prompt.
	      MAILPATH
		     A colon ( : ) separated list  of  file  names.   If  this
		     variable  is  set, then the shell informs the user of any
		     modifications to the specified files that	have  occurred
		     within the last MAILCHECK seconds.	 Each file name can be
		     followed by a ?  and a message that will be printed.  The
		     message will undergo parameter expansion, command substi‐
		     tution, and arithmetic substitution with the variable  $_
		     defined  as  the  name of the file that has changed.  The
		     default message is you have mail in $_.
	      PATH   The search path for commands (see Execution below).   The
		     user  may not change PATH if executing under rksh (except
		     in .profile).
	      PS1    The value of this	variable  is  expanded	for  parameter
		     expansion, command substitution, and arithmetic substitu‐
		     tion to define the primary prompt string which by default
		     is	 ``$''.	 The character !  in the primary prompt string
		     is replaced by the command number (see  Command  Re-entry
		     below).   Two successive occurrences of !	will produce a
		     single !  when the prompt string is printed.
	      PS2    Secondary prompt string, by default ``> ''.
	      PS3    Selection prompt string used within  a  select  loop,  by
		     default ``#? ''.
	      PS4    The  value	 of  this  variable  is expanded for parameter
		     evaluation, command substitution, and arithmetic  substi‐
		     tution  and precedes each line of an execution trace.  By
		     default, PS4 is ``+ ''.  In addition when PS4  is	unset,
		     the execution trace prompt is also ``+ ''.
	      SHELL  The pathname of the shell is kept in the environment.  At
		     invocation, if the basename  of  this  variable  is  rsh,
		     rksh,  or krsh, then the shell becomes restricted.	 If it
		     is pfsh or pfksh, then the shell becomes a profile	 shell
		     (see pfexec(1)).
	      TIMEFORMAT
		     The  value	 of  this parameter is used as a format string
		     specifying how the timing information for pipelines  pre‐
		     fixed  with  the  time reserved word should be displayed.
		     The % character introduces	 a  format  sequence  that  is
		     expanded  to a time value or other information.  The for‐
		     mat sequences and their meanings are as follows.
		     %%	       A literal %.
		     %[p][l]R  The elapsed time in seconds.
		     %[p][l]U  The number of CPU seconds spent in user mode.
		     %[p][l]S  The number of CPU seconds spent in system mode.
		     %P	       The CPU percentage, computed as (U + S) / R.

		     The brackets denote optional portions.  The optional p is
		     a	digit  specifying  the	precision, the number of frac‐
		     tional digits after a decimal point.  A value of 0 causes
		     no decimal point or fraction to be output.	 At most three
		     places after the decimal point can be  displayed;	values
		     of p greater than 3 are treated as 3.  If p is not speci‐
		     fied, the value 3 is used.

		     The optional l specifies a longer format, including hours
		     if	 greater  than	zero, minutes, and seconds of the form
		     HHhMMmSS.FFs.  The value of p determines whether  or  not
		     the fraction is included.

		     All  other	 characters  are  output  without change and a
		     trailing newline is added.	 If unset, the default	value,
		     $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',  is	used.	If the
		     value is null, no timing information is displayed.

	      TMOUT  If set to a value greater than zero, TMOUT	 will  be  the
		     default timeout value for the read built-in command.  The
		     select compound command terminates	 after	TMOUT  seconds
		     when input is from a terminal.  Otherwise, the shell will
		     terminate if a line is not entered within the  prescribed
		     number  of	 seconds while reading from a terminal.	 (Note
		     that the shell can be compiled with a maximum  bound  for
		     this value which cannot be exceeded.)

	      VISUAL If	 the  value  of	 this  variable	 matches  the  pattern
		     *[Vv][Ii]*, then the vi option (see Special  Command  set
		     below)  is	 turned	 on.  If the value matches the pattern
		     *gmacs* , the gmacs option is turned on.	If  the	 value
		     matches the pattern *macs*, then the emacs option will be
		     turned on.	 The value of VISUAL overrides	the  value  of
		     EDITOR.

       The  shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set  at
       all  by	the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of sub‐
       stitutions  are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit	 null  fields  (""  or ′′) are retained.  Implicit null fields
       (those resulting from parameters that have no values or command substi‐
       tutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting
       from IFS are checked to see if they contain one or more	of  the	 brace
       patterns	 {*,*},	 {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
       or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are let‐
       ters  and  n1,n2,n3 are signed numbers and fmt is a format specified as
       used by printf.	In each case, fields are  created  by  prepending  the
       characters  before  the	{  and appending the characters after the } to
       each of the strings generated by the characters between the  {  and  }.
       The  resulting  fields  are  checked to see if they have any brace pat‐
       terns.

       In the first form, a field is created for each string between { and  ,,
       between	, and ,, and between , and }.  The string represented by * can
       contain embedded matching { and } without quoting.  Otherwise,  each  {
       and } with * must be quoted.

       In  the	seconds form, l1 and l2 must both be either upper case or both
       be lower case characters in the C locale.  In this case a field is cre‐
       ated for each character from l1 thru l2.

       In  the remaining forms, a field is created for each number starting at
       n1 and continuing until it reaches n2 incrementing n1 by n3.  The cases
       where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth‐
       erwise.	If forms which specify %fmt any format flags, widths and  pre‐
       cisions	can  be	 specified  and	 fmt  can end in any of the specifiers
       cdiouxX.	 For  example,	{a,z}{1..5..3%02d}{b..c}x  expands  to	the  8
       fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following  splitting, each field is scanned for the characters ∗, ?, (,
       and [ unless the -f option has been set.	 If one	 of  these  characters
       appears, then the word is regarded as a pattern.	 Each file name compo‐
       nent that contains any pattern character is  replaced  with  a  lexico‐
       graphically  sorted  set	 of  names  that matches the pattern from that
       directory.  If no file name is found that  matches  the	pattern,  then
       that  component of the filename is left unchanged unless the pattern is
       prefixed with ∼(N) in which case it is removed as described below.   If
       FIGNORE	is set, then each file name component that matches the pattern
       defined by the value of FIGNORE is ignored when generating the matching
       filenames.   The	 names .  and ..  are also ignored.  If FIGNORE is not
       set, the character .  at the start of each file name component will  be
       ignored unless the first character of the pattern corresponding to this
       component is the character .  itself.  Note, that  for  other  uses  of
       pattern matching the / and .  are not treated specially.

	      ∗	     Matches any string, including the null string.  When used
		     for filename expansion, if the globstar option is on, two
		     adjacent  ∗'s  by itself will match all files and zero or
		     more directories and subdirectories.  If followed by a  /
		     then only directories and subdirectories will match.
	      ?	     Matches any single character.
	      [...]  Matches  any  one	of the enclosed characters.  A pair of
		     characters separated by - matches any character lexically
		     between the pair, inclusive.  If the first character fol‐
		     lowing the opening [ is a !  or ^ then any character  not
		     enclosed  is matched.  A - can be included in the charac‐
		     ter set by putting it as the first or last character.
		     Within [ and ], character classes can be  specified  with
		     the  syntax [:class:] where class is one of the following
		     classes defined in the ANSI-C standard: (Note  that  word
		     is equivalent to alnum plus the character _.)
		     alnum  alpha  blank  cntrl	 digit graph lower print punct
		     space upper word xdigit
		     Within [ and ], an equivalence  class  can	 be  specified
		     with  the	syntax [=c=] which matches all characters with
		     the same primary collation weight (as defined by the cur‐
		     rent  locale) as the character c.	Within [ and ], [.sym‐
		     bol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns	 separated  from  each
       other  with  a & or ⎪.  A & signifies that all patterns must be matched
       whereas ⎪ requires that only one pattern be  matched.   Composite  pat‐
       terns can be formed with one or more of the following sub-patterns:
	      ?(pattern-list)
		     Optionally matches any one of the given patterns.
	      *(pattern-list)
		     Matches zero or more occurrences of the given patterns.
	      +(pattern-list)
		     Matches one or more occurrences of the given patterns.
	      {n}(pattern-list)
		     Matches n occurrences of the given patterns.
	      {m,n}(pattern-list)
		     Matches  from  m  to n occurrences of the given patterns.
		     If m is omitted, 0 will be used.	If  n  is  omitted  at
		     least m occurrences will be matched.
	      @(pattern-list)
		     Matches exactly one of the given patterns.
	      !(pattern-list)
		     Matches anything except one of the given patterns.
       By  default, each pattern, or sub-pattern will match the longest string
       possible consistent with generating the longest overall match.  If more
       than  one  match is possible, the one starting closest to the beginning
       of the string will be chosen.   However, for each of the above compound
       patterns	 a  -  can be inserted in front of the ( to cause the shortest
       match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash	 char‐
       acter  \ is treated specially even when inside a character class.   All
       ANSI-C character escapes are recognized and match the specified charac‐
       ter.  In addition the following escape sequences are recognized:
	      \d     Matches any character in the digit class.
	      \D     Matches any character not in the digit class.
	      \s     Matches any character in the space class.
	      \S     Matches any character not in the space class.
	      \w     Matches any character in the word class.
	      \W     Matches any character not in the word class.

       A  pattern  of the form %(pattern-pair(s)) is a sub-pattern that can be
       used to match nested character expressions.  Each pattern-pair is a two
       character sequence which cannot contain & or ⎪.	The first pattern-pair
       specifies the starting and ending characters for the match.  Each  sub‐
       sequent	pattern-pair represents the beginning and ending characters of
       a nested group that will be skipped over	 when  counting	 starting  and
       ending  character  matches.  The behavior is unspecified when the first
       character of a pattern-pair is alpha-numeric except for the following:
	      D	     Causes the ending character to terminate the  search  for
		     this pattern without finding a match.
	      E	     Causes  the  ending  character  to	 be  interpreted as an
		     escape character.
	      L	     Causes the ending character to be interpreted as a	 quote
		     character causing all characters to be ignored when look‐
		     ing for a match.
	      Q	     Causes the ending character to be interpreted as a	 quote
		     character	causing	 all  characters other than any escape
		     character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching  }
       is  found not counting any { or } that is inside a double quoted string
       or preceded by the escape character \.  Without	the  {}	 this  pattern
       matches any C language string.

       Each  sub-pattern in a composite pattern is numbered, starting at 1, by
       the location of the ( within the pattern.  The sequence \n, where n  is
       a  single  digit	 and \n comes after the n-th. sub-pattern, matches the
       same string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the  form	∼(options:pat‐
       tern-list),  where  either  options  or	:pattern-list  can be omitted.
       Unlike the other compound patterns, these sub-patterns are not  counted
       in  the	numbered  sub-patterns.	  :pattern-list	 must  be  omitted for
       options F, G, N , and V below.  If options is present, it  can  consist
       of one or more of the following:
	      +	     Enable the following options.  This is the default.
	      -	     Disable the following options.
	      E	     The  remainder  of	 the  pattern  uses  extended  regular
		     expression syntax like the egrep(1) command.
	      F	     The remainder of the  pattern  uses  fgrep(1)  expression
		     syntax.
	      G	     The  remainder  of the pattern uses basic regular expres‐
		     sion syntax like the grep(1) command.
	      K	     The remainder of the pattern uses shell  pattern  syntax.
		     This is the default.
	      N	     This  is  ignored.	  However, when it is the first letter
		     and is used with file name	 generation,  and  no  matches
		     occur, the file pattern expands to the empty string.
	      X	     The  remainder  of	 the  pattern  uses  augmented regular
		     expression syntax like the xgrep(1) command.
	      P	     The remainder of the pattern uses perl(1) regular expres‐
		     sion  syntax.   Not all perl regular expression syntax is
		     currently implemented.
	      V	     The remainder  of	the  pattern  uses  System  V  regular
		     expression syntax.
	      i	     Treat the match as case insensitive.
	      g	     File the longest match (greedy).  This is the default.
	      l	     Left anchor the pattern.  This is the default for K style
		     patterns.
	      r	     Right anchor the pattern.	This  is  the  default	for  K
		     style patterns.
       If both options and :pattern-list are specified, then the options apply
       only to	pattern-list.  Otherwise, these options remain in effect until
       they  are disabled by a subsequent ∼(...) or at the end of the sub-pat‐
       tern containing ∼(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special	meaning	 to  the shell and causes termination of a word unless
       quoted.	A character may be quoted (i.e., made to stand for itself)  by
       preceding  it with a \.	The pair \new-line is removed.	All characters
       enclosed between a pair of single quote marks (′′) that is not preceded
       by  a  $	 are  quoted.	A single quote cannot appear within the single
       quotes.	A single quoted string preceded by an unquoted $ is  processed
       as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
	      Expands to the collating element name.

       Inside  double  quote  marks  (""),  parameter and command substitution
       occur and \ quotes the characters \, `, ", and $.  A $ in  front	 of  a
       double  quoted string will be ignored in the "C" or "POSIX" locale, and
       may cause the string to be replaced by a locale specific string	other‐
       wise.   The  meaning  of $∗ and $@ is identical when not quoted or when
       used as a variable assignment value or as a file name.	However,  when
       used  as a command argument, "$∗" is equivalent to "$1d$2d...", where d
       is the first character of the IFS variable, whereas "$@" is  equivalent
       to  "$1" "$2" ....  Inside grave quote marks (``), \ quotes the charac‐
       ters \, `, and $.  If the grave quotes occur within double quotes, then
       \ also quotes the character ".

       The  special  meaning  of  reserved  words or aliases can be removed by
       quoting any character of the reserved word.  The recognition  of	 func‐
       tion  names or built-in command names listed below cannot be altered by
       quoting them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation for  arithmetic	 substitution,
       to  evaluate  an	 arithmetic command, to evaluate an indexed array sub‐
       script, and to evaluate arguments to the built-in  commands  shift  and
       let.   Evaluations  are performed using double precision floating point
       arithmetic or long double precision floating  point  for	 systems  that
       provide	this  data  type.   Floating point constants follow the ANSI-C
       programming language floating point conventions.	  The  floating	 point
       constants Nan and Inf can be use to represent "not a number" and infin‐
       ity respectively.  Integer constants follow the ANSI-C programming lan‐
       guage  integer constant conventions although only single byte character
       constants are recognized and character casts are	 not  recognized.   In
       addition	 constants can be of the form [base#]n where base is a decimal
       number between two and sixty-four representing the arithmetic base  and
       n  is a number in that base.  The digits above 9 are represented by the
       lower case letters, the upper case letters, @, and _ respectively.  For
       bases  less than or equal to 36, upper and lower case characters can be
       used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associa‐
       tivity  of  expression as the C language.  All the C language operators
       that apply to floating point quantities can be used.  In addition,  the
       operator	 **  can be used for exponentiation.  It has higher precedence
       than multiplication and is left associative.   In  addition,  when  the
       value of an arithmetic variable or sub-expression can be represented as
       a long integer, all C language integer  arithmetic  operations  can  be
       performed.   Variables  can  be referenced by name within an arithmetic
       expression without using the parameter expansion syntax.	 When a	 vari‐
       able is referenced, its value is evaluated as an arithmetic expression.

       Any  of	the  following	math  library functions that are in the C math
       library can be used within an arithmetic expression:

       abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos  cosh
       erf erfc exp exp2 expm1 fabs fpclassify fdim finite floor fma fmax fmin
       fmod hypot ilogb int isfinite sinf isnan isnormal issubnormal  issubor‐
       dered  iszero  j0  j1 jn lgamma log log10 log2 logb nearbyint nextafter
       nexttoward pow remainder rint round scanb signbit  sin  sinh  sqrt  tan
       tanh  tgamma  trunc  y0	y1 yn In addition, arithmetic functions can be
       define as shell functions with a variant of the function name syntax,

       function .sh.math.name ident ... { list ;}
	      where name is the function name used in the  arithmetic  expres‐
	      sion  and each identifier, ident is a name reference to the long
	      double  precision	 floating  point  argument.   The   value   of
	      .sh.value	 when  the function returns is the value of this func‐
	      tion.  User defined functions can take up	 to  3	arguments  and
	      override C math library functions.

       An internal representation of a variable as a double precision floating
       point can be specified with the -E [n], -F [n], or -X [n] option of the
       typeset	special	 built-in command.  The -E option causes the expansion
       of the value to be represented using scientific	notation  when	it  is
       expanded.  The optional option argument n defines the number of signif‐
       icant figures.  The -F option causes the expansion to be represented as
       a floating decimal number when it is expanded.  The -X option cause the
       expansion to be represented using the %a format defined	by  ISO	 C-99.
       The  optional  option argument n defines the number of places after the
       decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified  with
       the  -i	[n]  option  of	 the  typeset  special	built-in command.  The
       optional option argument n specifies an arithmetic base to be used when
       expanding the variable.	If you do not specify an arithmetic base, base
       10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable	 with  the  -E, -F, -X, or -i attribute.  Assigning a floating
       point number to a variable whose type is an integer  causes  the	 frac‐
       tional part to be truncated.

   Prompting.
       When  used interactively, the shell prompts with the value of PS1 after
       expanding it for parameter expansion, command substitution, and	arith‐
       metic substitution, before reading a command.  In addition, each single
       !  in the prompt is replaced by the command number.  A !!  is  required
       to place !  in the prompt.  If at any time a new-line is typed and fur‐
       ther input is needed to complete a command, then the  secondary	prompt
       (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A  conditional  expression is used with the [[ compound command to test
       attributes of files and to compare strings.  Field splitting  and  file
       name generation are not performed on the words between [[ and ]].  Each
       expression can be constructed from one or more of the  following	 unary
       or binary expressions:
       string True, if string is not null.
       -a file
	      Same as -e below.	 This is obsolete.
       -b file
	      True, if file exists and is a block special file.
       -c file
	      True, if file exists and is a character special file.
       -d file
	      True, if file exists and is a directory.
       -e file
	      True, if file exists.
       -f file
	      True, if file exists and is an ordinary file.
       -g file
	      True, if file exists and it has its setgid bit set.
       -k file
	      True, if file exists and it has its sticky bit set.
       -n string
	      True, if length of string is non-zero.
       -o ?option
	      True, if option named option is a valid option name.
       -o option
	      True, if option named option is on.
       -p file
	      True, if file exists and is a fifo special file or a pipe.
       -r file
	      True, if file exists and is readable by current process.
       -s file
	      True, if file exists and has size greater than zero.
       -t fildes
	      True,  if	 file  descriptor number fildes is open and associated
	      with a terminal device.
       -u file
	      True, if file exists and it has its setuid bit set.
       -v name
	      True, if variable name is a valid variable name and is set.
       -w file
	      True, if file exists and is writable by current process.
       -x file
	      True, if file exists and is executable by current	 process.   If
	      file exists and is a directory, then true if the current process
	      has permission to search in the directory.
       -z string
	      True, if length of string is zero.
       -L file
	      True, if file exists and is a symbolic link.
       -h file
	      True, if file exists and is a symbolic link.
       -N file
	      True, if file exists and the modification time is	 greater  than
	      the last access time.
       -O file
	      True,  if	 file  exists and is owned by the effective user id of
	      this process.
       -G file
	      True, if file exists and its group matches the  effective	 group
	      id of this process.
       -R name
	      True if variable name is a name reference.
       -S file
	      True, if file exists and is a socket.
       file1 -nt file2
	      True, if file1 exists and file2 does not, or file1 is newer than
	      file2.
       file1 -ot file2
	      True, if file2 exists and file1 does not, or file1 is older than
	      file2.
       file1 -ef file2
	      True, if file1 and file2 exist and refer to the same file.
       string == pattern
	      True,  if	 string	 matches  pattern.  Any part of pattern can be
	      quoted to cause it to be matched as a string.  With a successful
	      match  to	 a  pattern, the .sh.match array variable will contain
	      the match and sub-pattern matches.
       string = pattern
	      Same as == above, but is obsolete.
       string != pattern
	      True, if string does not match pattern.  When the string matches
	      the  pattern the .sh.match array variable will contain the match
	      and sub-pattern matches.
       string =∼ ere
	      True if string matches the  pattern  ∼(E)ere  where  ere	is  an
	      extended regular expression.
       string1 < string2
	      True,  if	 string1  comes before string2 based on ASCII value of
	      their characters.
       string1 > string2
	      True, if string1 comes after string2 based  on  ASCII  value  of
	      their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
	      True, if exp1 is equal to exp2.
       exp1 -ne exp2
	      True, if exp1 is not equal to exp2.
       exp1 -lt exp2
	      True, if exp1 is less than exp2.
       exp1 -gt exp2
	      True, if exp1 is greater than exp2.
       exp1 -le exp2
	      True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
	      True, if exp1 is greater than or equal to exp2.

       In  each	 of  the  above expressions, if file is of the form /dev/fd/n,
       where n is an integer, then the test is applied to the open file	 whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
	      True, if expression is true.  Used to group expressions.
       ! expression
	      True if expression is false.
       expression1 && expression2
	      True, if expression1 and expression2 are both true.
       expression1 ⎪⎪ expression2
	      True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output  may	be  redirected
       using  a	 special notation interpreted by the shell.  The following may
       appear anywhere in a simple-command or may precede or follow a  command
       and  are	 not  passed on to the invoked command.	 Command substitution,
       parameter expansion, and arithmetic substitution occur before  word  or
       digit  is used except as noted below.  File name generation occurs only
       if the shell is interactive and the  pattern  matches  a	 single	 file.
       Field splitting is not performed.

       In  each	 of  the  following  redirections,  if	file  is  of  the form
       /dev/sctp/host/port, /dev/tcp/host/port, or  /dev/udp/host/port,	 where
       host is a hostname or host address, and port is a service given by name
       or an integer port number, then the redirection attempts to make a tcp,
       sctp or udp connection to the corresponding socket.

       No  intervening	space is allowed between the characters of redirection
       operators.

       <word	     Use file word as standard input (file descriptor 0).

       >word	     Use file word as standard output (file descriptor 1).  If
		     the  file does not exist then it is created.  If the file
		     exists, and the noclobber option is on,  this  causes  an
		     error; otherwise, it is truncated to zero length.

       >|word	     Same as >, except that it overrides the noclobber option.

       >;word	     Write  output  to	a temporary file.  If the command com‐
		     pletes successfully rename it to word, otherwise,	delete
		     the  temporary  file.   >;word  cannot  be	 used with the
		     exec(2).  built-in.

       >>word	     Use file word as standard output.	If  the	 file  exists,
		     then  output  is  appended to it (by first seeking to the
		     end-of-file); otherwise, the file is created.

       <>word	     Open file word for reading and writing as	standard  out‐
		     put.

       <>;word	     The  same	as <>word except that if the command completes
		     successfully, word is truncated to the offset at  command
		     completion.   <>;word  cannot  be	used with the exec(2).
		     built-in.

       <<[-]word     The shell input is read up to a line that is the same  as
		     word after any quoting has been removed, or to an end-of-
		     file.  No parameter substitution,	command	 substitution,
		     arithmetic	 substitution  or file name generation is per‐
		     formed on word.  The resulting document, called  a	 here-
		     document,	becomes	 the standard input.  If any character
		     of word is quoted, then no interpretation is placed  upon
		     the  characters  of  the  document;  otherwise, parameter
		     expansion, command substitution, and arithmetic substitu‐
		     tion  occur,  \new-line is ignored, and \ must be used to
		     quote the characters \, $, `.  If - is  appended  to  <<,
		     then all leading tabs are stripped from word and from the
		     document.	If # is appended to <<,	 then  leading	spaces
		     and tabs will be stripped off the first line of the docu‐
		     ment and up to an equivalent indentation will be stripped
		     from  the	remaining  lines and from word.	 A tab stop is
		     assumed to occur at every 8 columns for the  purposes  of
		     determining the indentation.

       <<<word	     A	short  form of here document in which word becomes the
		     contents of the here-document after any parameter	expan‐
		     sion,  command  substitution, and arithmetic substitution
		     occur.

       <&digit	     The standard input is  duplicated	from  file  descriptor
		     digit  (see  dup(2)).   Similarly for the standard output
		     using >&digit.

       <&digit-	     The file descriptor given by digit is moved  to  standard
		     input.  Similarly for the standard output using >&digit-.

       <&-	     The standard input is closed.  Similarly for the standard
		     output using >&-.

       <&p	     The input from the co-process is moved to standard input.

       >&p	     The output to the co-process is moved to standard output.

       <#((expr))    Evaluate arithmetic expression  expr  and	position  file
		     descriptor	 0 to the resulting value bytes from the start
		     of the file.  The variables CUR and EOF evaluate  to  the
		     current  offset  and end-of-file offset respectively when
		     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line  contain‐
		     ing pattern.

       <##pattern    The  same	as <# except that the portion of the file that
		     is skipped is copied to standard output.

       If one of the above is preceded by a digit, with no intervening	space,
       then  the  file	descriptor number referred to is that specified by the
       digit (instead of the default 0 or 1).  If one of the above, other than
       >&- and the ># and <# forms, is preceded by {varname} with no interven‐
       ing space, then a file descriptor number > 10 will be selected  by  the
       shell  and stored in the variable varname.  If >&- or the any of the >#
       and <# forms is preceded by {varname} the value of varname defines  the
       file descriptor to close or position.  For example:

	      ... 2>&1

       means  file  descriptor 2 is to be opened for writing as a duplicate of
       file descriptor 1 and

	      exec {n}<file

       means open file named file for reading and store	 the  file  descriptor
       number in variable n.

       The  order  in  which  redirections  are specified is significant.  The
       shell evaluates each redirection in  terms  of  the  (file  descriptor,
       file) association at the time of evaluation.  For example:

	      ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).	 If the order of redirections were reversed, file descriptor 2
       would be associated with the terminal (assuming file descriptor	1  had
       been) and then file descriptor 1 would be associated with file fname.

       If  a  command is followed by & and job control is not active, then the
       default standard input for the command is  the  empty  file  /dev/null.
       Otherwise,  the environment for the execution of a command contains the
       file descriptors of the invoking	 shell	as  modified  by  input/output
       specifications.

   Environment.
       The  environment (see environ(7)) is a list of name-value pairs that is
       passed to an executed program in the same  way  as  a  normal  argument
       list.   The  names  must	 be  identifiers  and the values are character
       strings.	 The shell interacts with the environment in several ways.  On
       invocation,  the shell scans the environment and creates a variable for
       each name found, giving it the corresponding value and  attributes  and
       marking	it export.  Executed commands inherit the environment.	If the
       user modifies the values of these variables or creates new ones,	 using
       the export or typeset -x commands, they become part of the environment.
       The environment seen by any executed command is thus  composed  of  any
       name-value pairs originally inherited by the shell, whose values may be
       modified by the current shell, plus any additions which must  be	 noted
       in export or typeset -x commands.

       The  environment for any simple-command or function may be augmented by
       prefixing it with one or more variable assignments.  A variable assign‐
       ment argument is a word of the form identifier=value.  Thus:

	      TERM=450 cmd args			 and
	      (export TERM; TERM=450; cmd args)

       are  equivalent	(as  far  as  the  above execution of cmd is concerned
       except for special built-in commands listed below - those that are pre‐
       ceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed in the environment, even if they occur after the	command	 name.
       The following first prints a=b c and then c:

	      echo a=b c
	      set -k
	      echo a=b c
       This  feature  is  intended for use with scripts written for early ver‐
       sions of the shell and its use in new scripts is strongly  discouraged.
       It is likely to disappear someday.

   Functions.
       For  historical	reasons,  there	 are two ways to define functions, the
       name() syntax and the function name syntax, described in	 the  Commands
       section	above.	 Shell	functions  are	read in and stored internally.
       Alias names are resolved when the function is read.  Functions are exe‐
       cuted like commands with the arguments passed as positional parameters.
       (See Execution below.)

       Functions defined by the function name syntax and called by  name  exe‐
       cute  in the same process as the caller and share all files and present
       working directory with the caller.  Traps  caught  by  the  caller  are
       reset  to  their	 default action inside the function.  A trap condition
       that is not caught or ignored by the function causes  the  function  to
       terminate  and  the condition to be passed on to the caller.  A trap on
       EXIT set inside a function is executed in the environment of the caller
       after the function completes.  Ordinarily, variables are shared between
       the calling program and the function.   However,	 the  typeset  special
       built-in	 command  used within a function defines local variables whose
       scope includes the current function.  They can be passed	 to  functions
       that  they  call in the variable assignment list that precedes the call
       or as arguments passed as name  references.   Errors  within  functions
       return control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function name syntax that are invoked with the .	 special built-in  are
       executed	 in the caller's environment and share all variables and traps
       with the caller.	 Errors within these  function	executions  cause  the
       script that contains them to abort.

       The  special  built-in  command	return is used to return from function
       calls.

       Function names can be listed with the -f or +f option  of  the  typeset
       special	built-in command.  The text of functions, when available, will
       also be listed with -f.	Functions can be undefined with the -f	option
       of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions that need to be defined across separate  invocations  of  the
       shell  should  be  placed  in a directory and the FPATH variable should
       contain the name of this directory.  They may also be specified in  the
       ENV file.

   Discipline Functions.
       Each  variable  can  have  zero or more discipline functions associated
       with it.	 The shell initially understands  the  discipline  names  get,
       set,  append,  and  unset but can be added when defining new types.  On
       most systems others can be added at run	time  via  the	C  programming
       interface  extension  provided by the builtin built-in utility.	If the
       get discipline is defined for a variable, it is	invoked	 whenever  the
       given  variable is referenced.  If the variable .sh.value is assigned a
       value inside the discipline  function,  the  referenced	variable  will
       evaluate to this value instead.	If the set discipline is defined for a
       variable, it is invoked whenever	 the  given  variable  is  assigned  a
       value.	If  the	 append	 discipline  is	 defined for a variable, it is
       invoked whenever a value is appended to the given variable.  The	 vari‐
       able  .sh.value	is given the value of the variable before invoking the
       discipline, and the variable will be assigned the  value	 of  .sh.value
       after  the discipline completes.	 If .sh.value is unset inside the dis‐
       cipline, then that value is unchanged.	If  the	 unset	discipline  is
       defined	for  a	variable, it is invoked whenever the given variable is
       unset.  The variable will not be unset unless it	 is  unset  explicitly
       from within this discipline function.

       The  variable  .sh.name contains the name of the variable for which the
       discipline function is called, .sh.subscript is the  subscript  of  the
       variable,  and  .sh.value  will contain the value being assigned inside
       the set discipline function.  The variable _  is	 a  reference  to  the
       variable	 including  the	 subscript  if	any.   For the set discipline,
       changing .sh.value will change the value that gets assigned.   Finally,
       the  expansion  ${var.name}, when name is the name of a discipline, and
       there is no variable of this name, is equivalent to the command substi‐
       tution ${ var.name;}.

   Name Spaces.
       Commands	 and  functions	 that  are  executed  as part of the list of a
       namespace command that modify variables or create new  ones,  create  a
       new variable whose name is the name of the name space as given by iden‐
       tifier preceded by ..  When a variable whose name  is  name  is	refer‐
       enced,  it  is first searched for using .identifier.name.  Similarly, a
       function defined by a command in the namespace list  is	created	 using
       the name space name  preceded by a ..

       When  the list of a namespace command contains a namespace command, the
       names of variables and functions that are created consist of the	 vari‐
       able or function name preceded by the list of identifiers each preceded
       by ..

       Outside of a name space, a variable or function created inside  a  name
       space can be referenced by preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.

   Type Variables.
       Typed  variables provide a way to create data structure and objects.  A
       type can be defined either by a shared library, by  the	enum  built-in
       command	described  below, or by using the new -T option of the typeset
       built-in command.  With the -T option of typeset, the type name, speci‐
       fied  as	 an  option  argument  to  -T, is set with a compound variable
       assignment that defines the  type.   Function  definitions  can	appear
       inside  the  compound  variable	assignment and these become discipline
       functions for this type	and  can  be  invoked  or  redefined  by  each
       instance	 of  the type.	The function name create is treated specially.
       It is invoked for each instance of the type that is created but is  not
       inherited and cannot be redefined for each instance.

       When  a	type  is  defined  a  special built-in command of that name is
       added.  These built-ins are declaration commands and  follow  the  same
       expansion rules as all the special built-in commands defined below that
       are preceded by ††.  These commands can	subsequently  be  used	inside
       further	type definitions.  The man page for these commands can be gen‐
       erated by using the --man  option  or  any  of  the  other  --  options
       described  with getopts.	 The -r, -a, -A, -h, and -S options of typeset
       are permitted with each of these new built-ins.

       An instance of a type is created by invoking the type name followed  by
       one  or	more instance names.  Each instance of the type is initialized
       with a copy of the sub-variables	 except	 for  sub-variables  that  are
       defined	with  the -S option.  Variables defined with the -S are shared
       by all instances of the type.  Each instance can change	the  value  of
       any  sub-variable  and  can also define new discipline functions of the
       same names as those defined by the type definition as well as any stan‐
       dard  discipline names.	No additional sub-variables can be defined for
       any instance.

       When defining a type, if the value of a sub-variable is not set and the
       -r  attribute is specified, it causes the sub-variable to be a required
       sub-variable.  Whenever an instance of a type is created, all  required
       sub-variables  must  be specified.  These sub-variables become readonly
       in each instance.

       When unset is invoked on a sub-variable	within	a  type,  and  the  -r
       attribute  has not been specified for this field, the value is reset to
       the default value associative with the type.  Invoking unset on a  type
       instance	 not  contained	 within another type deletes all sub-variables
       and the variable itself.

       A type definition can be derived from another type definition by defin‐
       ing  the first sub-variable name as _ and defining its type as the base
       type.  Any remaining definitions will be	 additions  and	 modifications
       that  apply  to the new type.  If the new type name is the same is that
       of the base type, the type will be replaced and the original type  will
       no longer be accessible.

       The typeset command with the -T and no option argument or operands will
       write all the type definitions to standard output in a form  that  that
       can be read in to create all they types.

   Jobs.
       If  the	monitor option of the set command is turned on, an interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs,  printed by the jobs command, and assigns them small integer num‐
       bers.  When a job is started asynchronously with &, the shell prints  a
       line which looks like:

	    [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       This paragraph and the next require features that are not in  all  ver‐
       sions  of UNIX and may not apply.  If you are running a job and wish to
       do something else you may hit the key ^Z (control-Z) which sends a STOP
       signal  to the current job.  The shell will then normally indicate that
       the job has been `Stopped', and print another  prompt.	You  can  then
       manipulate the state of this job, putting it in the background with the
       bg command, or run some other commands and then	eventually  bring  the
       job  back  into	the  foreground	 with the foreground command fg.  A ^Z
       takes effect immediately and is like an interrupt in that pending  out‐
       put and unread input are discarded when it is typed.

       A  job  being  run in the background will stop if it tries to read from
       the terminal.  Background jobs are normally allowed to produce  output,
       but this can be disabled by giving the command stty tostop.  If you set
       this tty option, then background jobs will stop when they try  to  pro‐
       duce output like they do when they try to read input.

       A  job pool is a collection of jobs started with list & associated with
       a name.

       There are several ways to refer to jobs in the shell.   A  job  can  be
       referred	 to  by	 the process id of any process of the job or by one of
       the following:
       %number
	      The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
	      The job number number in the job pool named by pool.
       %string
	      Any job whose command line begins with string.
       %?string
	      Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.  In addition, unless noted otherwise,  wherever  a
	      job  can	be specified, the name of a background job pool can be
	      used to represent all the jobs in that pool.

       The shell learns immediately whenever a process changes state.  It nor‐
       mally  informs  you  whenever  a job becomes blocked so that no further
       progress is possible, but only just before it prints a prompt.  This is
       done  so	 that  it  does	 not  otherwise disturb your work.  The notify
       option of the set command causes the shell to print  these  job	change
       messages as soon as they occur.

       When the monitor option is on, each background job that completes trig‐
       gers any trap set for CHLD.

       When you try to leave the shell while jobs are running or stopped,  you
       will  be warned that `You have stopped(running) jobs.'  You may use the
       jobs command to see what they are.  If  you  immediately	 try  to  exit
       again,  the shell will not warn you a second time, and the stopped jobs
       will be terminated.  When a login shell receives a HUP signal, it sends
       a  HUP  signal  to  each job that has not been disowned with the disown
       built-in command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the com‐
       mand is followed by & and the monitor option is not active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each  time  a command is read, the above substitutions are carried out.
       If the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.	Next, the com‐
       mand name is checked to see if it matches a user defined function.   If
       it  does,  the  positional  parameters  are saved and then reset to the
       arguments of the function call.	A function is  also  executed  in  the
       current shell process.  When the function completes or issues a return,
       the positional parameter list is restored.  For functions defined  with
       the  function  name syntax, any trap set on EXIT within the function is
       executed.  The exit value of a function is the value of the  last  com‐
       mand  executed.	If a command name is not a special built-in command or
       a user defined function, but it is one of the built-in commands	listed
       below, it is executed in the current shell process.

       The  shell  variables  PATH  followed by the variable FPATH defines the
       list of directories to search for the command name.  Alternative direc‐
       tory  names  are	 separated  by	a  colon  (:).	 The  default  path is
       /bin:/usr/bin: (specifying /bin, /usr/bin, and the current directory in
       that  order).   The  current  directory can be specified by two or more
       adjacent colons, or by a colon at the beginning	or  end	 of  the  path
       list.   If  the	command name contains a /, then the search path is not
       used.  Otherwise, each directory in the list of directories defined  by
       PATH and FPATH is checked in order.  If the directory being searched is
       contained in FPATH and contains a file whose name matches  the  command
       being  searched,	 then this file is loaded into the current shell envi‐
       ronment as if it were the argument to the . command  except  that  only
       preset  aliases	are expanded, and a function of the given name is exe‐
       cuted as described above.

       If this directory is not in FPATH the shell  first  determines  whether
       there is a built-in version of a command corresponding to a given path‐
       name and if so it is invoked in the current process.  If no built-in is
       found,  the shell checks for a file named .paths in this directory.  If
       found and there is a line of the form FPATH=path where  path  names  an
       existing	 directory  then  that directory is searched after immediately
       after the current directory as if it were found in the FPATH  variable.
       If path does not begin with /, it is checked for relative to the direc‐
       tory being searched.

       The .paths file is then checked	for a line of the form PLUGIN_LIB=lib‐
       name  [	:  libname  ]  ...  .	Each  library named by libname will be
       searched for as if it were an option argument to builtin -f, and if  it
       contains a built-in of the specified name this will be executed instead
       of a command by this name.  Any built-in loaded from  a	library	 found
       this  way  will	be associated with the directory containing the .paths
       file so it will only execute if not found in an earlier directory.

       Finally, the directory will be checked for a file of  the  given	 name.
       If  the	file  has  execute  permission but is not an a.out file, it is
       assumed to be a file containing shell commands.	A  separate  shell  is
       spawned	to  read  it.	All non-exported variables are removed in this
       case.  If the shell command file doesn't have read  permission,	or  if
       the  setuid and/or setgid bits are set on the file, then the shell exe‐
       cutes an agent whose job it is to set up the  permissions  and  execute
       the  shell with the shell command file passed down as an open file.  If
       the .paths contains a line of the form name=value in the first or  sec‐
       ond  line, then the environment variable name is modified by prepending
       the directory specified by value to the directory list.	 If  value  is
       not  an	absolute  directory, then it specifies a directory relative to
       the directory that the executable was found.  If the environment	 vari‐
       able  name  does	 not already exist it will be added to the environment
       list for the specified command.	A parenthesized command is executed in
       a sub-shell without removing non-exported variables.

   Command Re-entry.
       The  text  of  the  last HISTSIZE (default 512) commands entered from a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is  used if the HISTFILE variable is not set or if the file it names is
       not writable.  A shell can  access  the	commands  of  all  interactive
       shells which use the same named HISTFILE.  The built-in command hist is
       used to list or edit a portion of this file.  The portion of  the  file
       to be edited or listed can be selected by number or by giving the first
       character or characters of the command.	A single command or  range  of
       commands	 can be specified.  If you do not specify an editor program as
       an argument to hist then the value of the variable  HISTEDIT  is	 used.
       If  HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT
       is not defined, then /bin/ed is used.  The edited command(s) is printed
       and  re-executed	 upon leaving the editor unless you quit without writ‐
       ing.  The -s option (and in obsolete versions, the editor  name	-)  is
       used  to skip the editing phase and to re-execute the command.  In this
       case a substitution parameter of the form old=new can be used to modify
       the  command  before  execution.	 For example, with the preset alias r,
       which is aliased to ′hist -s′, typing `r bad=good  c'  will  re-execute
       the  most  recent command which starts with the letter c, replacing the
       first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal  device  is	simply
       typed  followed by a new-line (`RETURN' or `LINE FEED').	 If either the
       emacs, gmacs, or vi option is active, the user  can  edit  the  command
       line.   To  be  in  either  of  these  edit modes set the corresponding
       option.	An editing option is automatically selected each time the VIS‐
       UAL  or	EDITOR	variable is assigned a value ending in either of these
       option names.

       The editing features require that the user's terminal  accept  `RETURN'
       as  carriage return without line feed and that a space (` ') must over‐
       write the current character on the screen.

       Unless the multiline option is on, the editing modes implement  a  con‐
       cept  where  the	 user is looking through a window at the current line.
       The window width is the value of COLUMNS if it  is  defined,  otherwise
       80.   If	 the window width is too small to display the prompt and leave
       at least 8 columns to enter input, the prompt  is  truncated  from  the
       left.  If the line is longer than the window width minus two, a mark is
       displayed at the end of the window to notify the user.  As  the	cursor
       moves  and  reaches  the	 window boundaries the window will be centered
       about the cursor.  The mark is a > (<, *) if the line  extends  on  the
       right (left, both) side(s) of the window.

       The  search  commands  in  each edit mode provide access to the history
       file.  Only strings are matched, not patterns, although a leading ^  in
       the  string  restricts the match to begin at the first character in the
       line.

       Each of the edit modes has an operation to list the files  or  commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, ⎪, &, or (, and  the  word  does
       not  begin  with	 ∼ or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could  match  the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.	 If the partially entered word does  not  con‐
       tain  any  file expansion characters, a * is appended before generating
       these lists.  After displaying the generated list, the  input  line  is
       redrawn.	  These	 operations  are  called command name listing and file
       name listing, respectively.  There are additional operations,  referred
       to  as  command name completion and file name completion, which compute
       the list of matching commands or files, but  instead  of	 printing  the
       list,  replace  the current word with a complete or partial match.  For
       file name completion, if the match is unique, a / is  appended  if  the
       file is a directory and a space is appended if the file is not a direc‐
       tory.  Otherwise, the longest common prefix for all the matching	 files
       replaces	 the  word.   For command name completion, only the portion of
       the file names after the last / are used to find	 the  longest  command
       prefix.	 If  only  a single name matches this prefix, then the word is
       replaced with the command name followed by a space.  When using	a  tab
       for  completion	that  does  not yield a unique match, a subsequent tab
       will provide a numbered list  of	 matching  alternatives.   A  specific
       selection  can  be  made by entering the selection number followed by a
       tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys  as	 they  are  typed  and
       change  the  characters that are actually seen by the shell.  This trap
       is executed after each character (or sequence of	 characters  when  the
       first  character is ESC) is entered while reading from a terminal.  The
       variable .sh.edchar contains the character or character sequence	 which
       generated  the  trap.   Changing	 the  value  of .sh.edchar in the trap
       action causes the shell to behave as if the new value were entered from
       the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor
       at the time of the input.  The variable .sh.edmode is set to  ESC  when
       in  vi  insert  mode  (see below) and is null otherwise.	 By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar  it  will  cause  the
       shell to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only  difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the  point  needing  correction  and
       then inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation  for
       control	characters  is caret (^) followed by the character.  For exam‐
       ple, ^F is the notation for control F.  This is entered	by  depressing
       `f'  while  holding  down the `CTRL' (control) key.  The `SHIFT' key is
       not depressed.  (The notation ^?	 indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a  character.   For
       example,	 M-f  (pronounced  Meta f) is entered by depressing ESC (ascii
       033) followed by `f'.  (M-F would be the notation for ESC  followed  by
       `SHIFT' (capital) `F'.)

       All  edit  commands operate from any place on the line (not just at the
       beginning).  Neither the `RETURN' nor the `LINE FEED'  key  is  entered
       after edit commands except when noted.

       ^F	 Move cursor forward (right) one character.
       M-[C	 Move cursor forward (right) one character.
       M-f	 Move  cursor forward one word.	 (The emacs editor's idea of a
		 word is a string of characters consisting  of	only  letters,
		 digits and underscores.)
       ^B	 Move cursor backward (left) one character.
       M-[D	 Move cursor backward (left) one character.
       M-b	 Move cursor backward one word.
       ^A	 Move cursor to start of line.
       M-[H	 Move cursor to start of line.
       ^E	 Move cursor to end of line.
       M-[Y	 Move cursor to end of line.
       ^]char	 Move cursor forward to character char on current line.
       M-^]char	 Move cursor backward to character char on current line.
       ^X^X	 Interchange the cursor and mark.
       erase	 (User	defined erase character as defined by the stty(1) com‐
		 mand, usually ^H or #.)  Delete previous character.
       lnext	 (User defined	literal	 next  character  as  defined  by  the
		 stty(1)  command,  or	^V  if not defined.)  Removes the next
		 character's editing features (if any).
       ^D	 Delete current character.
       M-d	 Delete current word.
       M-^H	 (Meta-backspace) Delete previous word.
       M-h	 Delete previous word.
       M-^?	 (Meta-DEL) Delete previous word (if your interrupt  character
		 is ^?	(DEL, the default) then this command will not work).
       ^T	 Transpose  current  character	with  previous	character  and
		 advance the cursor in emacs  mode.   Transpose	 two  previous
		 characters in gmacs mode.
       ^C	 Capitalize current character.
       M-c	 Capitalize current word.
       M-l	 Change the current word to lower case.
       ^K	 Delete	 from  the cursor to the end of the line.  If preceded
		 by a numerical parameter whose value is less than the current
		 cursor	 position,  then  delete from given position up to the
		 cursor.  If preceded by a numerical parameter whose value  is
		 greater  than	the  current cursor position, then delete from
		 cursor up to given cursor position.
       ^W	 Kill from the cursor to the mark.
       M-p	 Push the region from the cursor to the mark on the stack.
       kill	 (User defined kill character as defined by the stty  command,
		 usually ^G or @.)  Kill the entire current line.  If two kill
		 characters are entered in  succession,	 all  kill  characters
		 from  then on cause a line feed (useful when using paper ter‐
		 minals).
       ^Y	 Restore last item removed from line. (Yank item back  to  the
		 line.)
       ^L	 Line feed and print current line.
       M-^L	 Clear the screen.
       ^@	 (Null character) Set mark.
       M-space	 (Meta space) Set mark.
       ^J	 (New line) Execute the current line.
       ^M	 (Return) Execute the current line.
       eof	 End-of-file  character,  normally ^D, is processed as an End-
		 of-file only if the current line is null.
       ^P	 Fetch previous command.  Each time ^P is entered the previous
		 command  back	in time is accessed.  Moves back one line when
		 not on the first line of a multi-line command.
       M-[A	 If the cursor is at the end of the line, it is equivalent  to
		 ^R with string set to the contents of the current line.  Oth‐
		 erwise, it is equivalent to ^P.
       M-<	 Fetch the least recent (oldest) history line.
       M->	 Fetch the most recent (youngest) history line.
       ^N	 Fetch next command line.  Each time ^N is  entered  the  next
		 command line forward in time is accessed.
       M-[B	 Equivalent to ^N.
       ^Rstring	 Reverse search history for a previous command line containing
		 string.  If a parameter of zero is given, the search is  for‐
		 ward.	 String is terminated by a `RETURN' or `NEW LINE'.  If
		 string is preceded by a ^, the matched line must  begin  with
		 string.   If  string  is  omitted, then the next command line
		 containing the most recent string is accessed.	 In this  case
		 a parameter of zero reverses the direction of the search.
       ^O	 Operate  -  Execute  the current line and fetch the next line
		 relative to current line from the history file.
       M-digits	 (Escape) Define numeric parameter, the digits are taken as  a
		 parameter  to	the  next command.  The commands that accept a
		 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
		 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter	 Soft-key  -  Your  alias list is searched for an alias by the
		 name _letter and if an alias of this  name  is	 defined,  its
		 value	will  be inserted on the input queue.  The letter must
		 not be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an	alias  by  the
		 name  __letter	 and  if an alias of this name is defined, its
		 value will be inserted on the input queue.  This can be  used
		 to program function keys on many terminals.
       M-.	 The  last  word  of  the  previous command is inserted on the
		 line.	If preceded by a numeric parameter, the value of  this
		 parameter  determines	which  word  to insert rather than the
		 last word.
       M-_	 Same as M-..
       M-*	 Attempt file name generation on the current word.  An	aster‐
		 isk is appended if the word doesn't match any file or contain
		 any special pattern characters.
       M-ESC	 Command or file name completion as described above.
       ^I tab	 Attempts command or file name completion as described	above.
		 If a partial completion occurs, repeating this will behave as
		 if M-= were entered.  If no match is found or	entered	 after
		 space, a tab is inserted.
       M-=	 If not preceded by a numeric parameter, it generates the list
		 of matching commands or file names as described above.	  Oth‐
		 erwise,  the  word  under  the cursor is replaced by the item
		 corresponding to the value of the numeric parameter from  the
		 most  recently generated command or file list.	 If the cursor
		 is not on a word, it is inserted instead.
       ^U	 Multiply parameter of next command by 4.
       \	 Escape next character.	 Editing characters, the user's erase,
		 kill  and  interrupt (normally ^?)  characters may be entered
		 in a command line or in a search string if preceded by	 a  \.
		 The \ removes the next character's editing features (if any).
       M-^V	 Display version of the shell.
       M-#	 If  the  line does not begin with a #, a # is inserted at the
		 beginning of the line and after each new-line, and  the  line
		 is entered.  This causes a comment to be inserted in the his‐
		 tory file.  If the line begins with a #, the # is deleted and
		 one # after each new-line is also deleted.

   Vi Editing Mode.
       There  are  two	typing modes.  Initially, when you enter a command you
       are in the input mode.  To edit, the user enters control mode by typing
       ESC (033) and moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.   Most	 control  com‐
       mands accept an optional repeat count prior to the command.

       When  in	 vi  mode  on  most systems, canonical processing is initially
       enabled and the command will be echoed again if the speed is 1200  baud
       or greater and it contains any control characters or less than one sec‐
       ond has elapsed since the prompt was printed.  The ESC character termi‐
       nates  canonical	 processing  for  the remainder of the command and the
       user can then modify the command line.  This scheme has the  advantages
       of canonical processing with the type-ahead echoing of raw mode.

       If  the option viraw is also set, the terminal will always have canoni‐
       cal processing disabled.	 This mode is implicit for systems that do not
       support	two  alternate	end of line delimiters, and may be helpful for
       certain terminals.

	Input Edit Commands
	      By default the editor is in input mode.
	      erase	(User defined erase character as defined by  the  stty
			command, usually ^H or #.)  Delete previous character.
	      ^W	Delete	the  previous  blank  separated word.  On some
			systems the viraw option may be required for  this  to
			work.
	      eof	As the first character of the line causes the shell to
			terminate unless the ignoreeof option is set.	Other‐
			wise this character is ignored.
	      lnext	(User defined literal next character as defined by the
			stty(1) or ^V if not defined.)	Removes the next char‐
			acter's	 editing  features  (if any).  On some systems
			the viraw option may be required for this to work.
	      \		Escape the next erase or kill character.
	      ^I tab	Attempts command or file name completion as  described
			above and returns to input mode.  If a partial comple‐
			tion occurs, repeating this will behave as if  =  were
			entered	 from  control	mode.  If no match is found or
			entered after space, a tab is inserted.
	Motion Edit Commands
	      These commands will move the cursor.
	      [count]l	Cursor forward (right) one character.
	      [count][C Cursor forward (right) one character.
	      [count]w	Cursor forward one alpha-numeric word.
	      [count]W	Cursor to the beginning of the next word that  follows
			a blank.
	      [count]e	Cursor to end of word.
	      [count]E	Cursor to end of the current blank delimited word.
	      [count]h	Cursor backward (left) one character.
	      [count][D Cursor backward (left) one character.
	      [count]b	Cursor backward one word.
	      [count]B	Cursor to preceding blank separated word.
	      [count]⎪	Cursor to column count.
	      [count]fc Find the next character c in the current line.
	      [count]Fc Find the previous character c in the current line.
	      [count]tc Equivalent to f followed by h.
	      [count]Tc Equivalent to F followed by l.
	      [count];	Repeats	 count	times,	the last single character find
			command, f, F, t, or T.
	      [count],	Reverses the last single character find command	 count
			times.
	      0		Cursor to start of line.
	      ^		Cursor to start of line.
	      [H	Cursor to first non-blank character in line.
	      $		Cursor to end of line.
	      [Y	Cursor to end of line.
	      %		Moves  to balancing (, ), {, }, [, or ].  If cursor is
			not on one of the above characters, the	 remainder  of
			the  line  is searched for the first occurrence of one
			of the above characters first.
	Search Edit Commands
	      These commands access your command history.
	      [count]k	Fetch previous command.	 Each time k  is  entered  the
			previous command back in time is accessed.
	      [count]-	Equivalent to k.
	      [count][A If  cursor  is at the end of the line it is equivalent
			to / with string^set to the contents  of  the  current
			line.  Otherwise, it is equivalent to k.
	      [count]j	Fetch  next  command.  Each time j is entered the next
			command forward in time is accessed.
	      [count]+	Equivalent to j.
	      [count][B Equivalent to j.
	      [count]G	The command number count is fetched.  The  default  is
			the least recent history command.
	      /string	Search backward through history for a previous command
			containing string.  String is terminated by a `RETURN'
			or  `NEW LINE'.	  If  string  is  preceded by a ^, the
			matched line must begin with  string.	If  string  is
			null, the previous string will be used.
	      ?string	Same  as  /  except that search will be in the forward
			direction.
	      n		Search for next match of the last pattern to  /	 or  ?
			commands.
	      N		Search	for  next match of the last pattern to / or ?,
			but in reverse direction.
	Text Modification Edit Commands
	      These commands will modify the line.
	      a		Enter input mode and  enter  text  after  the  current
			character.
	      A		Append text to the end of the line.  Equivalent to $a.
	      [count]cmotion
	      c[count]motion
			Delete	current	 character  through the character that
			motion would move the cursor to and enter input	 mode.
			If  motion  is	c, the entire line will be deleted and
			input mode entered.
	      C		Delete the current character through the end  of  line
			and enter input mode.  Equivalent to c$.
	      S		Equivalent to cc.
	      [count]s	Replace characters under the cursor in input mode.
	      D		Delete	the current character through the end of line.
			Equivalent to d$.
	      [count]dmotion
	      d[count]motion
			Delete current character through  the  character  that
			motion	would  move  to.   If motion is d , the entire
			line will be deleted.
	      i		Enter input mode and insert text  before  the  current
			character.
	      I		Insert text before the beginning of the line.  Equiva‐
			lent to 0i.
	      [count]P	Place the previous text modification before  the  cur‐
			sor.
	      [count]p	Place the previous text modification after the cursor.
	      R		Enter  input mode and replace characters on the screen
			with characters you type overlay fashion.
	      [count]rc Replace the count character(s) starting at the current
			cursor position with c, and advance the cursor.
	      [count]x	Delete current character.
	      [count]X	Delete preceding character.
	      [count].	Repeat the previous text modification command.
	      [count]∼	Invert	the case of the count character(s) starting at
			the current cursor position and advance the cursor.
	      [count]_	Causes the count word of the previous  command	to  be
			appended  and  input  mode  entered.  The last word is
			used if count is omitted.
	      *		Causes an * to be appended to  the  current  word  and
			file name generation attempted.	 If no match is found,
			it rings the bell.  Otherwise, the word is replaced by
			the matching pattern and input mode is entered.
	      \		Command or file name completion as described above.
	Other Edit Commands
	      Miscellaneous commands.
	      [count]ymotion
	      y[count]motion
			Yank  current  character through character that motion
			would move the cursor to and puts them into the delete
			buffer.	 The text and cursor are unchanged.
	      yy	Yanks the entire line.
	      Y		Yanks  from  current position to end of line.  Equiva‐
			lent to y$.
	      u		Undo the last text modifying command.
	      U		Undo all the text modifying commands performed on  the
			line.
	      [count]v	Returns	 the  command hist -e ${VISUAL:-${EDITOR:-vi}}
			count in the input buffer.  If count is omitted,  then
			the current line is used.
	      ^L	Line  feed and print current line.  Has effect only in
			control mode.
	      ^J	(New line) Execute the	current	 line,	regardless  of
			mode.
	      ^M	(Return) Execute the current line, regardless of mode.
	      #		If  the	 first	character  of the command is a #, then
			this command deletes this # and each # that follows  a
			newline.   Otherwise, sends the line after inserting a
			# in front of each line in the	command.   Useful  for
			causing the current line to be inserted in the history
			as a comment  and  uncommenting	 previously  commented
			commands in the history file.
	      [count]=	If  count  is  not specified, it generates the list of
			matching commands or file names	 as  described	above.
			Otherwise,  the	 word under the the cursor is replaced
			by the count item from	the  most  recently  generated
			command or file list.  If the cursor is not on a word,
			it is inserted instead.
	      @letter	Your alias list is searched for an alias by  the  name
			_letter	 and  if an alias of this name is defined, its
			value will be inserted on the input queue for process‐
			ing.
	      ^V	Display version of the shell.

   Built-in Commands.
       The  following  simple-commands	are  executed  in  the	shell process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output  is written on file descriptor 1 and the exit status, when there
       is no syntax error, is zero.  Except for :, true, false, echo,  newgrp,
       and  login, all built-in commands accept -- to indicate end of options.
       They also interpret the option --man as a request to  display  the  man
       page onto standard error and -?	as a help request which prints a usage
       message on standard error.  Commands that are preceded by one or two  †
       symbols	are special built-in commands and are treated specially in the
       following ways:
       1.     Variable assignment lists preceding the command remain in effect
	      when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words  following a command preceded by †† that are in the format
	      of a variable assignment are expanded with the same rules	 as  a
	      variable assignment.  This means that tilde substitution is per‐
	      formed after the = sign and field splitting and file name gener‐
	      ation  are  not  performed.  These are called declaration built-
	      ins.

       † : [ arg ... ]
	      The command only expands parameters.

       † . name [ arg ... ]
	      If name is a function defined with the  function	name  reserved
	      word syntax, the function is executed in the current environment
	      (as if it had been defined with the name()  syntax.)   Otherwise
	      if  name	refers to a file, the file is read in its entirety and
	      the commands are executed in the current shell environment.  The
	      search path specified by PATH is used to find the directory con‐
	      taining the file.	 If any arguments arg are given,  they	become
	      the  positional  parameters  while processing the .  command and
	      the original positional parameters are restored upon completion.
	      Otherwise	 the  positional  parameters  are unchanged.  The exit
	      status is the exit status of the last command executed.

       †† alias [ -ptx ]  [ name[ =value  ] ] ...
	      alias with no arguments prints the list of aliases in  the  form
	      name=value  on  standard	output.	 The -p option causes the word
	      alias to be inserted before each one.  When one  or  more	 argu‐
	      ments  are  given, an alias is defined for each name whose value
	      is given.	 A trailing space in value causes the next word to  be
	      checked  for alias substitution.	The obsolete -t option is used
	      to set and list tracked aliases.	The value of a	tracked	 alias
	      is the full pathname corresponding to the given name.  The value
	      becomes undefined when the value of PATH is reset but the	 alias
	      remains  tracked.	  Without  the -t option, for each name in the
	      argument list for which no value is given, the name and value of
	      the  alias  is  printed.	 The obsolete -x option has no effect.
	      The exit status is non-zero if a name is given,  but  no	value,
	      and no alias has been defined for the name.

       bg [ job... ]
	      This  command is only on systems that support job control.  Puts
	      each specified job into the background.  The current job is  put
	      in  the  background  if  job  is	not specified.	See Jobs for a
	      description of the format of job.

       † break [ n ]
	      Exit from the enclosing for, while, until, or  select  loop,  if
	      any.  If n is specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
	      If  name	is  not	 specified, and no -f option is specified, the
	      built-ins are printed on standard output.	 The -s option	prints
	      only the special built-ins.  Otherwise, each name represents the
	      pathname whose basename is the name of the built-in.  The	 entry
	      point function name is determined by prepending b_ to the built-
	      in name.	A built-in specified by a pathname will only  be  exe‐
	      cuted  when that pathname would be found during the path search.
	      Built-ins found in libraries loaded via the .paths file will  be
	      associate	 with  the  pathname  of  the directory containing the
	      .paths file.

       The ISO C/C++ prototype is b_mycommand(int  argc,  char	*argv[],  void
       *context)  for  the builtin command mycommand where argv is array an of
       argc elements and context is an optional pointer to a Shell_t structure
       as described in <ast/shell.h>.
       Special	built-ins  cannot  be  bound to a pathname or deleted.	The -d
       option deletes each of the given built-ins.  On	systems	 that  support
       dynamic	loading,  the  -f option names a shared library containing the
       code for built-ins.  The shared library	prefix	and/or	suffix,	 which
       depend  on  the	system, can be omitted.	 Once a library is loaded, its
       symbols become available for subsequent invocations of builtin.	Multi‐
       ple libraries can be specified with separate invocations of the builtin
       command.	 Libraries are searched in the reverse order in which they are
       specified.   When  a  library is loaded, it looks for a function in the
       library whose name is lib_init() and  invokes  this  function  with  an
       argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
	      This  command  can be in either of two forms.  In the first form
	      it changes the current directory to arg.	If arg is - the direc‐
	      tory  is	changed to the previous directory.  The shell variable
	      HOME is the default arg.	The variable PWD is set to the current
	      directory.   The	shell  variable CDPATH defines the search path
	      for the directory containing arg.	 Alternative  directory	 names
	      are separated by a colon (:).  The default path is <null> (spec‐
	      ifying the current directory).  Note that the current  directory
	      is  specified  by a null path name, which can appear immediately
	      after the equal sign or between the  colon  delimiters  anywhere
	      else  in	the path list.	If arg begins with a / then the search
	      path is not used.	 Otherwise, each  directory  in	 the  path  is
	      searched for arg.
	      The  second form of cd substitutes the string new for the string
	      old in the current directory name, PWD, and tries to  change  to
	      this new directory.
	      By default, symbolic link names are treated literally when find‐
	      ing the directory name.  This is equivalent to  the  -L  option.
	      The  -P  option causes symbolic links to be resolved when deter‐
	      mining the directory.  The last instance of -L or -P on the com‐
	      mand line determines which method is used.
	      The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
	      Without  the  -v	or  -V options, command executes name with the
	      arguments given by arg.  The -p option causes a default path  to
	      be  searched  rather  than the one defined by the value of PATH.
	      Functions will not be searched for when finding name.  In	 addi‐
	      tion,  if name refers to a special built-in, none of the special
	      properties associated with the leading daggers will be  honored.
	      (For  example, the predefined alias redirect=′command exec′ pre‐
	      vents a script from terminating when an invalid  redirection  is
	      given.)	With  the -x option, if command execution would result
	      in a failure because there are too many arguments, errno	E2BIG,
	      the  shell will invoke command name multiple times with a subset
	      of the arguments on each invocation.  Arguments that occur prior
	      to  the  first word that expands to multiple arguments and after
	      the last word that expands to multiple arguments will be	passed
	      on each invocation.  The exit status will be the maximum invoca‐
	      tion exit status.	 With the -v option, command is equivalent  to
	      the  built-in  whence  command  described	 below.	 The -V option
	      causes command to act like whence -v.

       † continue [ n ]
	      Resume the next iteration of the enclosing for, while, until, or
	      select loop.  If n is specified, then resume at the n-th enclos‐
	      ing loop.

       disown [ job... ]
	      Causes the shell not to send a HUP signal to each given job,  or
	      all  active  jobs	 if  job is omitted, when a login shell termi‐
	      nates.

       echo [ arg ... ]
	      When the first arg does not begin with a	-,  and	 none  of  the
	      arguments	 contain  a  \, then echo prints each of its arguments
	      separated by a space and terminated by a	new-line.   Otherwise,
	      the  behavior  of	 echo  is system dependent and print or printf
	      described below should be	 used.	 See  echo(1)  for  usage  and
	      description.

       †† enum [ -i  ] type[=(value ...) ]
	      Creates a declaration command named type that is an integer type
	      that allows one of the specified values  as  enumeration	names.
	      If  =(value ...)	is omitted, then type must be an indexed array
	      variable with at least two elements and  the  values  are	 taken
	      from  this  array	 variable.   If -i is specified the values are
	      case insensitive.

       † eval [ arg ... ]
	      The arguments are read as input to the shell and	the  resulting
	      command(s) executed.

       † exec [ -c ] [ -a name ] [ arg ... ]
	      If  arg is given, the command specified by the arguments is exe‐
	      cuted in place of this shell without  creating  a	 new  process.
	      The -c option causes the environment to be cleared before apply‐
	      ing variable assignments associated with	the  exec  invocation.
	      The  -a  option causes name rather than the first arg, to become
	      argv[0] for the new process.  Input/output arguments may	appear
	      and affect the current process.  If arg is not given, the effect
	      of this command is to modify file descriptors as	prescribed  by
	      the  input/output	 redirection  list.   In  this	case, any file
	      descriptor numbers greater than 2	 that  are  opened  with  this
	      mechanism are closed when invoking another program.

       † exit [ n ]
	      Causes  the  shell  to exit with the exit status specified by n.
	      The value will be the least significant 8 bits of the  specified
	      status.	If  n  is omitted, then the exit status is that of the
	      last command executed.  An end-of-file will also cause the shell
	      to  exit	except for a shell which has the ignoreeof option (see
	      set below) turned on.

       †† export [ -p ] [ name[=value] ] ...
	      If name is not given, the names and values of each variable with
	      the  export  attribute  are  printed with the values quoted in a
	      manner that allows them to be re-input.  The export  command  is
	      the  same	 as  typeset -x except that if you use export within a
	      function, no local variable is created.  The  -p	option	causes
	      the  word export to be inserted before each one.	Otherwise, the
	      given names are marked for automatic export to  the  environment
	      of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
	      This  command is only on systems that support job control.  Each
	      job specified is brought to the foreground and waited for in the
	      specified order.	Otherwise, the current job is brought into the
	      foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
	      Prints the current value of the configuration parameter given by
	      name.   The  configuration  parameters  are  defined by the IEEE
	      POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See  pathconf(2)
	      and  sysconf(2).)	 The pathname argument is required for parame‐
	      ters whose value depends on the location in the file system.  If
	      no  arguments  are given, getconf prints the names and values of
	      the current configuration parameters.  The pathname  /  is  used
	      for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
	      Checks arg for legal options.  If arg is omitted, the positional
	      parameters are used.  An option argument begins with a + or a -.
	      An  option not beginning with + or - or the argument -- ends the
	      options.	Options beginning with + are only recognized when opt‐
	      string  begins  with  a  +.  optstring contains the letters that
	      getopts recognizes.  If a letter is followed by a :, that option
	      is  expected  to have an argument.  The options can be separated
	      from the argument by blanks.  The option -?  causes  getopts  to
	      generate a usage message on standard error.  The -a argument can
	      be used to specify the name to use for the usage message,	 which
	      defaults to $0.
	      getopts  places  the next option letter it finds inside variable
	      vname each time it  is  invoked.	 The  option  letter  will  be
	      prepended	 with  a + when arg begins with a +.  The index of the
	      next arg is stored in OPTIND.  The option argument, if any, gets
	      stored in OPTARG.
	      A	 leading  : in optstring causes getopts to store the letter of
	      an invalid option in OPTARG, and to  set	vname  to  ?   for  an
	      unknown option and to : when a required option argument is miss‐
	      ing.  Otherwise, getopts prints an error message.	 The exit sta‐
	      tus is non-zero when there are no more options.
	      There is no way to specify any of the options :, +, -, ?, [, and
	      ].  The option # can only be specified as the first option.

       hist [ -e ename	] [ -nlr ] [ first [ last ] ]
       hist -s	[ old=new ] [ command ]
	      In the first form, a range of commands from  first  to  last  is
	      selected	from the last HISTSIZE commands that were typed at the
	      terminal.	 The arguments first and last may be  specified	 as  a
	      number  or  as  a	 string.   A string is used to locate the most
	      recent command starting with the given string.  A negative  num‐
	      ber  is used as an offset to the current command number.	If the
	      -l option is selected, the commands are listed on standard  out‐
	      put.   Otherwise,	 the editor program ename is invoked on a file
	      containing these keyboard commands.  If ename is	not  supplied,
	      then the value of the variable HISTEDIT is used.	If HISTEDIT is
	      not set, then FCEDIT (default /bin/ed) is used  as  the  editor.
	      When  editing  is complete, the edited command(s) is executed if
	      the changes have been saved.  If last is not specified, then  it
	      will be set to first.  If first is not specified, the default is
	      the previous command for	editing	 and  -16  for	listing.   The
	      option  -r  reverses the order of the commands and the option -n
	      suppresses command numbers when listing.	In  the	 second	 form,
	      command  is interpreted as first described above and defaults to
	      the last command executed.  The resulting	 command  is  executed
	      after the optional substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
	      Lists  information  about	 each given job; or all active jobs if
	      job is omitted.  The -l option lists process ids in addition  to
	      the  normal  information.	 The -n option only displays jobs that
	      have stopped or exited  since  last  notified.   The  -p	option
	      causes  only  the	 process  group	 to be listed.	See Jobs for a
	      description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -Ll [ sig ... ]
	      Sends either the TERM (terminate) signal or the specified signal
	      to the specified jobs or processes.  Signals are either given by
	      number with the -n option or by name  with  the  -s  option  (as
	      given  in	 <signal.h>,  stripped	of the prefix ``SIG'' with the
	      exception that SIGCLD is named CHLD).  For backward  compatibil‐
	      ity,  the	 n  and s can be omitted and the number or name placed
	      immediately after the -.	If the signal being sent is TERM (ter‐
	      minate)  or HUP (hangup), then the job or process will be sent a
	      CONT (continue) signal if it is stopped.	The argument  job  can
	      be  the  process	id of a process that is not a member of one of
	      the active jobs.	See Jobs for a description of  the  format  of
	      job.   In	 the  third  form,  kill -l, or kill -L, if sig is not
	      specified, the signal names are listed.  The -l option list only
	      the  signal names.  -L options lists each signal name and corre‐
	      sponding number.	Otherwise, for each sig that is	 a  name,  the
	      corresponding  signal  number is listed.	For each sig that is a
	      number, the signal name corresponding to the least significant 8
	      bits of sig is listed.

       let arg ...
	      Each  arg	 is  a separate arithmetic expression to be evaluated.
	      let only recognizes octal constants starting with 0 when the set
	      option  letoctal	is on.	See Arithmetic Evaluation above, for a
	      description of arithmetic expression evaluation.
	      The exit status is 0 if the value of the last expression is non-
	      zero, and 1 otherwise.

       † newgrp [ arg ... ]
	      Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
	      With  no	options or with option - or --, each arg is printed on
	      standard output.	The -f	option	causes	the  arguments	to  be
	      printed  as  described  by printf.  In this case, any e, n, r, R
	      options are ignored.  Otherwise, unless the -C, -R,  -r,	or  -v
	      are specified, the following escape conventions will be applied:
	      \a     The alert character (ascii 07).
	      \b     The backspace character (ascii 010).
	      \c     Causes print to end without processing more arguments and
		     not adding a new-line.
	      \f     The formfeed character (ascii 014).
	      \n     The new-line character (ascii 012).
	      \r     The carriage return character (ascii 015).
	      \t     The tab character (ascii 011).
	      \v     The vertical tab character (ascii 013).
	      \E     The escape character (ascii 033).
	      \\     The backslash character \.
	      \0x    The character defined by  the  1,	2,  or	3-digit	 octal
		     string given by x.

	      The  -R  option  will print all subsequent arguments and options
	      other than -n.  The -e causes the above escape conventions to be
	      applied.	 This is the default behavior.	It reverses the effect
	      of an earlier -r.	 The -p option	causes	the  arguments	to  be
	      written  onto the pipe of the process spawned with ⎪& instead of
	      standard output.	The -v option treats each arg  as  a  variable
	      name  and	 writes	 the  value  in	 the printf %B format.	The -C
	      option treats each arg as a variable name and writes  the	 value
	      in the printf %#B format.	 The -s option causes the arguments to
	      be written onto the history file	instead	 of  standard  output.
	      The -u option can be used to specify a one digit file descriptor
	      unit number unit on  which  the  output  will  be	 placed.   The
	      default is 1.  If the option -n is used, no new-line is added to
	      the output.

       printf format [ arg ... ]
	      The arguments arg are printed on standard output	in  accordance
	      with  the	 ANSI-C	 formatting  rules  associated with the format
	      string format.  If the number of arguments exceeds the number of
	      format  specifications,  the  format  string is reused to format
	      remaining arguments.  The following extensions can also be used:
	      %b     A %b format can be used instead of	 %s  to	 cause	escape
		     sequences	in  the	 corresponding	arg  to be expanded as
		     described in print.
	      %B     A %B option causes each of the arguments to be treated as
		     variable  names  and the binary value of variable will be
		     printed.  The alternate flag # causes a compound variable
		     to	 be  output on a single line.  This is most useful for
		     compound variables and variables whose attribute is -b.
	      %H     A %H format can be used instead of %s to cause characters
		     in	 arg  that are special in HTML and XML to be output as
		     their entity name.	 The alternate flag # formats the out‐
		     put for use as a URI.
	      %P     A	%P format can be used instead of %s to cause arg to be
		     interpreted as an	extended  regular  expression  and  be
		     printed as a shell pattern.
	      %R     A	%R format can be used instead of %s to cause arg to be
		     interpreted as a shell pattern and to be  printed	as  an
		     extended regular expression.
	      %q     A	%q  format  can	 be  used  instead  of %s to cause the
		     resulting string to be quoted in a	 manner	 than  can  be
		     reinput to the shell.  When q is preceded by the alterna‐
		     tive format specifier, #, the string is quoted in	manner
		     suitable as a field in a .csv format file.
	      %(date-format)T
		     A	%(date-format)T format can be use to treat an argument
		     as a date/time string and to format the date/time accord‐
		     ing  to  the  date-format as defined for the date(1) com‐
		     mand.
	      %Z     A %Z format will output a byte whose value is 0.
	      %d     The precision field of the %d format can be followed by a
		     .	and the output base.  In this case, the # flag charac‐
		     ter causes base# to be prepended.
	      #	     The # flag, when used with the %d format without an  out‐
		     put base, displays the output in powers of 1000 indicated
		     by one of the following suffixes: k M G T P E,  and  when
		     used  with the %i format displays the output in powers of
		     1024 indicated by one of the following suffixes: Ki Mi Gi
		     Ti Pi Ei.
	      =	     The  = flag centers the output within the specified field
		     width.
	      L	     The L flag, when used with the %c or %s  formats,	treats
		     precision as character width instead of byte count.
	      ,	     The  ,  flag,  when used with the %d or %f formats, sepa‐
		     rates groups of digits with the grouping delimiter (,  on
		     groups of 3 in the C locale.)

       pwd [ -LP ]
	      Outputs  the  value  of  the  current working directory.	The -L
	      option is the default; it prints the logical name of the current
	      directory.   If  the  -P option is given, all symbolic links are
	      resolved from the name.  The last instance of -L or  -P  on  the
	      command line determines which method is used.

       read  [	-ACSprsv  ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u
       unit] [ vname?prompt ] [ vname ... ]
	      The shell input mechanism.  One line is read and	is  broken  up
	      into  fields  using  the	characters  in IFS as separators.  The
	      escape character, \, is used to remove any special  meaning  for
	      the  next	 character  and	 for line continuation.	 The -d option
	      causes the read to continue to  the  first  character  of	 delim
	      rather  than  new-line.  The -n option causes at most n bytes to
	      read rather a full line but will return when reading from a slow
	      device  as soon as any characters have been read.	 The -N option
	      causes exactly n to be  read  unless  an	end-of-file  has  been
	      encountered  or the read times out because of the -t option.  In
	      raw mode, -r, the \ character is	not  treated  specially.   The
	      first  field is assigned to the first vname, the second field to
	      the second vname, etc., with leftover  fields  assigned  to  the
	      last vname.  When vname has the binary attribute and -n or -N is
	      specified, the bytes that are read are stored directly into  the
	      variable.	  If  the -v is specified, then the value of the first
	      vname will be used as a default value when reading from a termi‐
	      nal device.  The -A option causes the variable vname to be unset
	      and each field that is read to be stored in successive  elements
	      of  the  indexed array vname.  The -C option causes the variable
	      vname to be read as a compound variable.	Blanks will be ignored
	      when  finding  the  beginning  open  parenthesis.	 The -S option
	      causes the line to be treated like a record  in  a  .csv	format
	      file  so	that  double quotes can be used to allow the delimiter
	      character and the new-line character to appear within  a	field.
	      The  -p  option causes the input line to be taken from the input
	      pipe of a process spawned by the shell  using  ⎪&.   If  the  -s
	      option  is  present, the input will be saved as a command in the
	      history file.  The option -u can be used to specify a one	 digit
	      file descriptor unit unit to read from.  The file descriptor can
	      be opened with the exec special built-in command.	  The  default
	      value  of unit n is 0.  The option -t is used to specify a time‐
	      out in seconds when reading from a terminal or pipe.   If	 vname
	      is omitted, then REPLY is used as the default vname.  An end-of-
	      file with the -p option causes cleanup for this process so  that
	      another can be spawned.  If the first argument contains a ?, the
	      remainder of this word is used as a  prompt  on  standard	 error
	      when  the	 shell is interactive.	The exit status is 0 unless an
	      end-of-file is encountered or read has timed out.

       †† readonly [ -p ] [ vname[=value] ] ...
	      If vname is not given, the names and  values  of	each  variable
	      with the readonly attribute is printed with the values quoted in
	      a manner that allows them to  be	re-inputted.   The  -p	option
	      causes the word readonly to be inserted before each one.	Other‐
	      wise, the given vnames are marked readonly and these names  can‐
	      not  be changed by subsequent assignment.	 When defining a type,
	      if the value of a readonly sub-variable is not defined the value
	      is required when creating each instance.

       † return [ n ]
	      Causes  a	 shell function or .  script to return to the invoking
	      script with the exit status specified by n.  The value  will  be
	      the  least  significant 8 bits of the specified status.  If n is
	      omitted, then the return status is that of the last command exe‐
	      cuted.   If  return  is  invoked	while not in a function or a .
	      script, then it behaves the same as exit.

       † set [ ±BCGabefhkmnoprstuvx ] [ ±o [ option ] ] ... [ ±A  vname	 ]   [
       arg ... ]
	      The options for this command have meaning as follows:
	      -A      Array  assignment.   Unset the variable vname and assign
		      values sequentially from the arg list.  If +A  is	 used,
		      the variable vname is not unset first.
	      -B      Enable  brace  pattern  field  generation.   This is the
		      default behavior.
	      -B      Enable brace group expansion.  On by default.
	      -C      Prevents redirection > from truncating  existing	files.
		      Files  that are created are opened with the O_EXCL mode.
		      Requires >⎪ to truncate a file when turned on.
	      -G      Causes the pattern ∗∗ by itself to match files and  zero
		      or  more	directories  and sub-directories when used for
		      file name generation.  If followed by a / only  directo‐
		      ries and sub-directories are matched.
	      -a      All  subsequent variables that are defined are automati‐
		      cally exported.
	      -b      Prints job completion messages as soon as	 a  background
		      job  changes  state  rather  than	 waiting  for the next
		      prompt.
	      -e      Unless contained in a ⎪⎪ or && command, or  the  command
		      following	 an  if while or until command or in the pipe‐
		      line following !, if a command has a non-zero exit  sta‐
		      tus,  execute the ERR trap, if set, and exit.  This mode
		      is disabled while reading profiles.
	      -f      Disables file name generation.
	      -h      Each command becomes a tracked alias when first  encoun‐
		      tered.
	      -k      (Obsolete). All variable assignment arguments are placed
		      in the environment for a command, not  just  those  that
		      precede the command name.
	      -m      Background jobs will run in a separate process group and
		      a line will print upon completion.  The exit  status  of
		      background jobs is reported in a completion message.  On
		      systems with job control, this option is turned on auto‐
		      matically for interactive shells.
	      -n      Read  commands  and check them for syntax errors, but do
		      not execute them.	 Ignored for interactive shells.
	      -o      The following argument  can  be  one  of	the  following
		      option names:
		      allexport
			      Same as -a.
		      errexit Same as -e.
		      bgnice  All background jobs are run at a lower priority.
			      This is the default mode.
		      braceexpand
			      Same as -B.
		      emacs   Puts you in an emacs style  in-line  editor  for
			      command entry.
		      globstar
			      Same as -G.
		      gmacs   Puts  you	 in  a	gmacs style in-line editor for
			      command entry.
		      ignoreeof
			      The shell will not  exit	on  end-of-file.   The
			      command exit must be used.
		      keyword Same as -k.
		      letoctal
			      The  let command allows octal constants starting
			      with 0.
		      markdirs
			      All directory names  resulting  from  file  name
			      generation have a trailing / appended.
		      monitor Same as -m.
		      multiline
			      The  built-in editors will use multiple lines on
			      the screen for lines that are  longer  than  the
			      width  of the screen.  This may not work for all
			      terminals.
		      noclobber
			      Same as -C.
		      noexec  Same as -n.
		      noglob  Same as -f.
		      nolog   Do not save function definitions in the  history
			      file.
		      notify  Same as -b.
		      nounset Same as -u.
		      pipefail
			      A	 pipeline  will	 not complete until all compo‐
			      nents of the pipeline have  completed,  and  the
			      return  value will be the value of the last non-
			      zero command to fail or zero if no  command  has
			      failed.
		      showme  When  enabled, simple commands or pipelines pre‐
			      ceded by a semicolon (;) will be displayed as if
			      the  xtrace  option were enabled but will not be
			      executed.	 Otherwise,  the  leading  ;  will  be
			      ignored.
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      trackall
			      Same as -h.
		      vi      Puts  you	 in  insert mode of a vi style in-line
			      editor until you hit the escape  character  033.
			      This  puts  you in control mode.	A return sends
			      the line.
		      viraw   Each character is processed as it is typed in vi
			      mode.
		      xtrace  Same as -x.
		      If  no  option name is supplied, then the current option
		      settings are printed.
	      -p      Disables processing of the $HOME/.profile file and  uses
		      the  file	 /etc/suid_profile  instead  of	 the ENV file.
		      This mode is on whenever the effective uid (gid) is  not
		      equal  to	 the  real uid (gid).  Turning this off causes
		      the effective uid and gid to be set to the real uid  and
		      gid.
	      -r      Enables  the  restricted	shell.	 This option cannot be
		      unset once set.
	      -s      Sort the positional parameters lexicographically.
	      -t      (Obsolete).  Exit after reading and executing  one  com‐
		      mand.
	      -u      Treat unset parameters as an error when substituting.
	      -v      Print shell input lines as they are read.
	      -x      Print commands and their arguments as they are executed.
	      --      Do  not  change any of the options; useful in setting $1
		      to a value beginning with -.   If	 no  arguments	follow
		      this option then the positional parameters are unset.

	      As an obsolete feature, if the first arg is - then the -x and -v
	      options are turned off and the next arg is treated as the	 first
	      argument.	  Using	 +  rather  than  - causes these options to be
	      turned off.  These options can also be used upon	invocation  of
	      the  shell.   The	 current  set  of  options may be found in $-.
	      Unless -A is specified, the remaining arguments  are  positional
	      parameters  and  are  assigned,  in  order, to $1 $2 ....	 If no
	      arguments are given, then the names and values of all  variables
	      are printed on the standard output.

       † shift [ n ]
	      The  positional  parameters  from $n+1 ...  are renamed $1 ... ,
	      default n is 1.  The parameter n can be any  arithmetic  expres‐
	      sion  that evaluates to a non-negative number less than or equal
	      to $#.

       sleep seconds
	      Suspends execution for the number of decimal  seconds  or	 frac‐
	      tions of a second given by seconds.

       † trap [ -p ] [ action ] [ sig ] ...
	      The  -p  option causes the trap action associated with each trap
	      as specified by the arguments to	be  printed  with  appropriate
	      quoting.	 Otherwise,  action will be processed as if it were an
	      argument to eval when the shell receives	signal(s)  sig.	  Each
	      sig can be given as a number or as the name of the signal.  Trap
	      commands are executed in order of signal number.	Any attempt to
	      set  a trap on a signal that was ignored on entry to the current
	      shell is ineffective.  If action is omitted and the first sig is
	      a	 number,  or if action is -, then the trap(s) for each sig are
	      reset to their original values.  If action is  the  null	string
	      then  this signal is ignored by the shell and by the commands it
	      invokes.	If sig is ERR then action will be executed whenever  a
	      command has a non-zero exit status.  If sig is DEBUG then action
	      will be executed before each command.  The variable  .sh.command
	      will  contain  the  contents  of	the  current command line when
	      action is running.  If the exit status of the trap is 2 the com‐
	      mand  will  not  be executed.  If the exit status of the trap is
	      255 and inside a function or a dot script, the function  or  dot
	      script  will return.  If sig is 0 or EXIT and the trap statement
	      is executed inside the body of a function defined with the func‐
	      tion  name syntax, then the command action is executed after the
	      function completes.  If sig is 0 or EXIT for a trap set  outside
	      any  function  then  the command action is executed on exit from
	      the shell.  If sig is KEYBD, then action will be executed	 when‐
	      ever  a key is read while in emacs, gmacs, or vi mode.  The trap
	      command with no arguments prints a list of  commands  associated
	      with each signal number.

       An  exit	 or  return without an argument in a trap action will preserve
       the exit status of the command that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       †† typeset [ ±ACHSfblmnprtux ] [ ±EFLRXZi[n] ]	[ +-M  [ mapname ] ] [
       -T  [ tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]
	] ...
	      Sets attributes and values for shell  variables  and  functions.
	      When  invoked  inside  a function defined with the function name
	      syntax, a new instance of the variable vname is created, and the
	      variable's  value	 and  type are restored when the function com‐
	      pletes.  The following list of attributes may be specified:
	      -A     Declares vname to be an  associative  array.   Subscripts
		     are strings rather than arithmetic expressions.
	      -C     causes each vname to be a compound variable.  value names
		     a compound variable it is copied into vname.   Otherwise,
		     it unsets each vname.
	      -a     Declares vname to be an indexed array.  If type is speci‐
		     fied, it must be the name of an enumeration type  created
		     with the enum command and it allows enumeration constants
		     to be used as subscripts.
	      -E     Declares vname to be a double  precision  floating	 point
		     number.   If n is non-zero, it defines the number of sig‐
		     nificant figures that  are	 used  when  expanding	vname.
		     Otherwise, ten significant figures will be used.
	      -F     Declares  vname  to  be a double precision floating point
		     number.  If n is  non-zero,  it  defines  the  number  of
		     places after the decimal point that are used when expand‐
		     ing vname.	 Otherwise ten places after the decimal	 point
		     will be used.
	      -H     This  option  provides  UNIX to host-name file mapping on
		     non-UNIX machines.
	      -L     Left justify and remove leading blanks from value.	 If  n
		     is non-zero, it defines the width of the field, otherwise
		     it is determined by the  width  of	 the  value  of	 first
		     assignment.   When	 the  variable	is  assigned to, it is
		     filled on the right with blanks or truncated,  if	neces‐
		     sary,  to	fit  into  the field.  The -R option is turned
		     off.
	      -M     Use the character mapping mapping defined by  wctrans(3).
		     such  as  tolower	and  toupper when assigning a value to
		     each of the specified operands.  When mapping  is	speci‐
		     fied  and	there are not operands, all variables that use
		     this mapping are written to standard output.   When  map‐
		     ping  is  omitted	and  there are no operands, all mapped
		     variables are written to standard output.
	      -R     Right justify and fill with leading blanks.  If n is non-
		     zero,  it defines the width of the field, otherwise it is
		     determined by the width of the value of first assignment.
		     The  field	 is  left filled with blanks or truncated from
		     the end if the variable is reassigned.  The -L option  is
		     turned off.
	      -S     When used within the assign_list of a type definition, it
		     causes the specified sub-variable to  be  shared  by  all
		     instances	of  the	 type.	 When  used  inside a function
		     defined with the function reserved	 word,	the  specified
		     variables	will  have  function static scope.  Otherwise,
		     the variable is unset prior to processing the  assignment
		     list.
	      -T     If	 followed  by  tname, it creates a type named by tname
		     using the compound assignment assign_list to tname.  Oth‐
		     erwise,  it  writes  all the type definitions to standard
		     output.
	      -X     Declares vname to be a double  precision  floating	 point
		     number  and expands using the %a format of ISO-C99.  If n
		     is non-zero, it defines the number of  hex	 digits	 after
		     the  radix	 point that is used when expanding vname.  The
		     default is 10.
	      -Z     Right justify and fill with leading zeros	if  the	 first
		     non-blank	character is a digit and the -L option has not
		     been set.	Remove leading zeros if the -L option is  also
		     set.   If	n  is  non-zero,  it  defines the width of the
		     field, otherwise it is determined by  the	width  of  the
		     value of first assignment.
	      -f     The  names	 refer	to function names rather than variable
		     names.  No assignments can be made	 and  the  only	 other
		     valid  options are -S, -t, -u and -x.  The -S can be used
		     with discipline functions defined in a type  to  indicate
		     that  the function is static.  For a static function, the
		     same method will be used by all instances of that type no
		     matter which instance references it.  In addition, it can
		     only use value of variables from the original type	 defi‐
		     nition.   These  discipline functions cannot be redefined
		     in any type instance.  The -t option turns	 on  execution
		     tracing  for  this	 function.   The -u option causes this
		     function to be marked undefined.  The FPATH variable will
		     be	 searched  to  find  the  function definition when the
		     function is referenced.  If no options other than	-f  is
		     specified, then the function definition will be displayed
		     on standard output.  If +f is specified, then a line con‐
		     taining  the  function  name  followed by a shell comment
		     containing the line number and  path  name	 of  the  file
		     where  this  function  was defined, if any, is displayed.
		     The exit status can be  used  to  determine  whether  the
		     function is defined so that typeset -f .sh.math.name will
		     return 0 when math function name is defined and  non-zero
		     otherwise.
	      -b     The  variable  can hold any number of bytes of data.  The
		     data can be text or binary.  The value is represented  by
		     the  base64  encoding  of the data.  If -Z is also speci‐
		     fied, the size in bytes of the data in the buffer will be
		     determined	 by  the  size associated with the -Z.	If the
		     base64 string assigned results in more data, it  will  be
		     truncated.	 Otherwise, it will be filled with bytes whose
		     value is zero.  The printf format %B can be used to  out‐
		     put  the actual data in this buffer instead of the base64
		     encoding of the data.
	      -h     Used within type definitions to add information when gen‐
		     erating  information  about  the  sub-variable on the man
		     page.  It is ignored when used outside of a type  defini‐
		     tion.   When  used	 with -f the information is associated
		     with the corresponding discipline function.
	      -i     Declares vname to be represented internally  as  integer.
		     The  right	 hand side of an assignment is evaluated as an
		     arithmetic expression when assigning to an integer.  If n
		     is	 non-zero, it defines the output arithmetic base, oth‐
		     erwise the output base will be ten.
	      -l     Used with -i, -E or -F, to indicate long integer, or long
		     float.   Otherwise,  all  upper-case  characters are con‐
		     verted to lower-case.   The  upper-case  option,  -u,  is
		     turned off.  Equivalent to -M tolower .
	      -m     moves  or renames the variable.  The value is the name of
		     a variable whose value will be moved to vname.  The orig‐
		     inal  variable  will  be  unset.  Cannot be used with any
		     other options.
	      -n     Declares vname to be a reference to  the  variable	 whose
		     name  is defined by the value of variable vname.  This is
		     usually used to reference a variable  inside  a  function
		     whose  name  has  been  passed as an argument.  Cannot be
		     used with any other options.
	      -p     The name, attributes and values for the given vnames  are
		     written  on standard output in a form that can be used as
		     shell input.  If +p is specified, then the values are not
		     displayed.
	      -r     The given vnames are marked readonly and these names can‐
		     not be changed by subsequent assignment.
	      -t     Tags the variables.  Tags are user definable and have  no
		     special meaning to the shell.
	      -u     When  given  along	 with  -i, specifies unsigned integer.
		     Otherwise, all lower-case	characters  are	 converted  to
		     upper-case.   The	lower-case  option, -l, is turned off.
		     Equivalent to -M toupper .
	      -x     The given vnames are marked for automatic export  to  the
		     environment of subsequently-executed commands.  Variables
		     whose names contain a .  cannot be exported.

	      The -i attribute cannot be specified along with -R, -L,  -Z,  or
	      -f.

	      Using + rather than - causes these options to be turned off.  If
	      no vname arguments are given, a list of vnames  (and  optionally
	      the values) of the variables is printed.	(Using + rather than -
	      keeps the values from being  printed.)   The  -p	option	causes
	      typeset followed by the option letters to be printed before each
	      name rather than the names of the options.  If any option	 other
	      than  -p	is  given,  only those variables which have all of the
	      given options are printed.  Otherwise, the vnames and attributes
	      of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
	      Set  or display a resource limit.	 The available resource limits
	      are listed below.	 Many systems do not support one  or  more  of
	      these  limits.   The  limit for a specified resource is set when
	      limit is specified.  The value of limit can be a number  in  the
	      unit specified below with each resource, or the value unlimited.
	      The -H and -S options specify whether the hard limit or the soft
	      limit  for  the  given  resource is set.	A hard limit cannot be
	      increased once it is set.	 A soft limit can be increased	up  to
	      the  value  of the hard limit.  If neither the H nor S option is
	      specified, the limit applies  to	both.	The  current  resource
	      limit  is printed when limit is omitted.	In this case, the soft
	      limit is printed unless H is  specified.	 When  more  than  one
	      resource	is  specified, then the limit name and unit is printed
	      before the value.
	      -a     Lists all of the current resource limits.
	      -c     The number of 512-byte blocks on the size of core dumps.
	      -d     The number of K-bytes on the size of the data area.
	      -f     The number of 512-byte blocks on files that can be	 writ‐
		     ten  by  the current process or by child processes (files
		     of any size may be read).
	      -m     The number of K-bytes on the size of physical memory.
	      -n     The number of file descriptors plus 1.
	      -p     The number of 512-byte blocks for pipe buffering.
	      -s     The number of K-bytes on the size of the stack area.
	      -t     The number of CPU seconds to be used by each process.
	      -v     The number of K-bytes for virtual memory.

	      If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
	      The user file-creation mask is set to mask (see umask(2)).  mask
	      can  either  be an octal number or a symbolic value as described
	      in chmod(1).  If a symbolic value is given, the new umask	 value
	      is  the complement of the result of applying mask to the comple‐
	      ment of the previous umask value.	 If mask is omitted, the  cur‐
	      rent  value  of  the  mask is printed.  The -S option causes the
	      mode to be printed as a symbolic value.  Otherwise, the mask  is
	      printed in octal.

       † unalias [ -a ] name ...
	      The  aliases  given  by  the  list of names are removed from the
	      alias list.  The -a option causes all the aliases to be unset.

       †unset [ -fnv ] vname ...
	      The variables given by the list of vnames are unassigned,	 i.e.,
	      except  for  sub-variables  within  a  type,  their  values  and
	      attributes are erased.  For sub-variables of a type, the	values
	      are  reset to the default value from the type definition.	 Read‐
	      only variables cannot be unset.  If the -f option is  set,  then
	      the  names  refer	 to  function names.  If the -v option is set,
	      then the names refer to variable names.  The -f option overrides
	      -v.   If	-n is set and name is a name reference, then name will
	      be unset rather than  the	 variable  that	 it  references.   The
	      default  is  equivalent  to  -v.	 Unsetting  LINENO, MAILCHECK,
	      OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their spe‐
	      cial meaning even if they are subsequently assigned to.

       wait [ job ... ]
	      Wait  for	 the  specified job and report its termination status.
	      If job is not given, then all currently active  child  processes
	      are  waited  for.	  The exit status from this command is that of
	      the last process waited for if job is specified; otherwise it is
	      zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
	      For each name, indicate how it would be interpreted if used as a
	      command name.
	      The -v option produces a more verbose  report.   The  -f	option
	      skips  the  search  for  functions.   The	 -p option does a path
	      search for name even if name is  an  alias,  a  function,	 or  a
	      reserved	word.	The -p option turns off the -v option.	The -a
	      option is similar to the -v option but  causes  all  interpreta‐
	      tions of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero ($0) is -, then the shell is assumed to be a login shell and  com‐
       mands  are  read from /etc/profile and then from either .profile in the
       current directory or $HOME/.profile, if either file exists.  Next,  for
       interactive shells, commands are read from the file named by performing
       parameter expansion, command substitution, and arithmetic  substitution
       on  the	value  of the environment variable ENV if the file exists.  If
       the -s option is not present and arg and a file	by  the	 name  of  arg
       exists,	then  it  reads	 and  executes this script.  Otherwise, if the
       first arg does not contain a /, a path search is performed on the first
       arg  to	determine  the	name of the script to execute.	The script arg
       must have execute permission and any setuid and setgid settings will be
       ignored.	  If  the script is not found on the path, arg is processed as
       if it named a built-in command or function.  Commands are then read  as
       described  below;  the  following  options are interpreted by the shell
       when it is invoked:

       -D      Do not execute the script, but output the set of double	quoted
	       strings	preceded  by a $.  These strings are needed for local‐
	       ization of the script to different locales.
       -E      Reads the file named by the ENV variable or by $HOME/.kshrc  if
	       not defined after the profiles.
       -c	 If  the -c option is present, then commands are read from the
		 first arg.  Any remaining arguments become positional parame‐
		 ters starting at 0.
       -s	 If  the  -s option is present or if no arguments remain, then
		 commands are read from the  standard  input.	Shell  output,
		 except	 for  the output of the Special Commands listed above,
		 is written to file descriptor 2.
       -i	 If the -i option is present or if the shell input and	output
		 are  attached	to  a terminal (as told by tcgetattr(2)), then
		 this shell is interactive.  In this case TERM is ignored  (so
		 that  kill  0 does not kill an interactive shell) and INTR is
		 caught and ignored (so that wait is ).	 In all cases, QUIT is
		 ignored by the shell.
       -r	 If the -r option is present, the shell is a restricted shell.
       -D	 A  list of all double quoted strings that are preceded by a $
		 will be printed on standard output and the shell  will	 exit.
		 This  set  of strings will be subject to language translation
		 when the locale is not C or POSIX.  No commands will be  exe‐
		 cuted.

       -P	 If  -P or -o profile is present, the shell is a profile shell
		 (see pfexec(1)).

       -R filename
		 The -R filename option is used to generate a cross  reference
		 database that can be used by a separate utility to find defi‐
		 nitions and references for variables and commands.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh  is	 used  to  set up login names and execution environments whose
       capabilities are more controlled than those of the standard shell.  The
       actions	of rksh are identical to those of ksh, except that the follow‐
       ing are disallowed:
	      Unsetting the restricted option.
	      changing directory (see cd(1)),
	      setting or unsetting the value  or  attributes  of  SHELL,  ENV,
	      FPATH, or PATH,
	      specifying path or command names containing /,
	      redirecting output (>, >|, <>, and >>).
	      adding or deleting built-in commands.
	      using command -p to invoke a command.

       The  restrictions  above	 are enforced after .profile and the ENV files
       are interpreted.

       When a command to be executed is found to be a  shell  procedure,  rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user shell procedures that have access to the full power of  the	 stan‐
       dard  shell,  while  imposing  a	 limited menu of commands; this scheme
       assumes that the end-user does not have write and  execute  permissions
       in the same directory.

       The  net	 effect	 of these rules is that the writer of the .profile has
       complete control over user  actions,  by	 performing  guaranteed	 setup
       actions	and leaving the user in an appropriate directory (probably not
       the login directory).

       The system administrator often sets up a directory of  commands	(e.g.,
       /usr/rbin) that can be safely invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-interac‐
       tively,	then execution of the shell file is abandoned unless the error
       occurs inside a subshell in which case the subshell is abandoned.  Oth‐
       erwise,	the shell returns the exit status of the last command executed
       (see also the exit command above).  Run time  errors  detected  by  the
       shell  are  reported  by	 printing the command or function name and the
       error condition.	 If the line number that  the  error  occurred	on  is
       greater than one, then the line number is also printed in square brack‐
       ets ([]) after the command or function name.

FILES
       /etc/profile
	      The system wide initialization file, executed for login shells.

       $HOME/.profile
	      The personal initialization  file,  executed  for	 login	shells
	      after /etc/profile.

       $HOME/..kshrc
	      Default  personal	 initialization file, executed for interactive
	      shells when ENV is not set.

       /etc/suid_profile
	      Alternative initialization file, executed instead	 of  the  per‐
	      sonal  initialization  file  when the real and effective user or
	      group id do not match.

       /dev/null
	      NULL device

SEE ALSO
       cat(1), cd(1), chmod(1), cut(1), egrep(1), echo(1),  emacs(1),  env(1),
       fgrep(1),  gmacs(1),  grep(1),  newgrp(1), pfexec(1), stty(1), test(1),
       umask(1),  vi(1),  dup(2),  exec(2),  fork(2),  getpwnam(3),  ioctl(2),
       lseek(2),   paste(1),   pathconf(2),   pipe(2),	sysconf(2),  umask(2),
       ulimit(2), wait(2), wctrans(3), rand(3),	 a.out(5),  profile(5),	 envi‐
       ron(7).

       Morris  I. Bolsky and David G. Korn, The New KornShell Command and Pro‐
       gramming Language, Prentice Hall, 1995.

       POSIX - Part 2: Shell and  Utilities,  IEEE  Std	 1003.2-1992,  ISO/IEC
       9945-2, IEEE, 1993.

CAVEATS
       If  a  command  is  executed,  and then a command with the same name is
       installed in a directory in the search path before the directory	 where
       the  original  command  was  found, the shell will continue to exec the
       original command.  Use the -t option of the alias  command  to  correct
       this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe char‐
       acter ⎪.

       Using the hist built-in command within a compound  command  will	 cause
       the whole command to disappear from the history file.

       The  built-in  command  . file reads the whole file before any commands
       are executed.  Therefore, alias and unalias commands in the  file  will
       not apply to any commands defined in the file.

       Traps  are  not	processed  while  a  job  is  waiting for a foreground
       process.	 Thus, a trap on CHLD won't be executed until  the  foreground
       job terminates.

       It  is  a good idea to leave a space after the comma operator in arith‐
       metic expressions to prevent the comma from being  interpreted  as  the
       decimal point character in certain locales.

									KSH(1)
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