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KSH(1)				 User commands				KSH(1)

NAME
       ksh - Public domain Korn shell

SYNOPSIS
       ksh [±abCefhikmnprsuvxX] [±o option] [ [ -c command-string [command-
       name] | -s | file ] [argument ...] ]

DESCRIPTION
       ksh is a command interpreter that is intended for both interactive  and
       shell  script  use.   Its  command  language is a superset of the sh(1)
       shell language.

   Shell Startup
       The following options can be specified only on the command line:

       -c command-string
	      the shell executes the command(s) contained in command-string

       -i     interactive mode — see below

       -l     login shell — see below interactive mode — see below

       -s     the shell reads commands from  standard  input;  all  non-option
	      arguments are positional parameters

       -r     restricted mode — see below

       In  addition  to	 the  above, the options described in the set built-in
       command can also be used on the command line.

       If neither the -c nor the -s options  are  specified,  the  first  non-
       option  argument	 specifies the name of a file the shell reads commands
       from; if there are no non-option arguments, the	shell  reads  commands
       from  standard input.  The name of the shell (i.e., the contents of the
       $0) parameter is determined as follows: if the -c option	 is  used  and
       there is a non-option argument, it is used as the name; if commands are
       being read from a file, the file is used as  the	 name;	otherwise  the
       name the shell was called with (i.e., argv[0]) is used.

       A  shell	 is  interactive  if the -i option is used or if both standard
       input and standard error are attached to a tty.	An  interactive	 shell
       has  job control enabled (if available), ignores the INT, QUIT and TERM
       signals, and prints prompts before  reading  input  (see	 PS1  and  PS2
       parameters).   For non-interactive shells, the trackall option is on by
       default (see set command below).

       A shell is restricted if the -r option is used or if either  the	 base‐
       name of the name the shell is invoked with or the SHELL parameter match
       the pattern *r*sh (e.g.,	 rsh,  rksh,  rpdksh,  etc.).	The  following
       restrictions come into effect after the shell processes any profile and
       $ENV files:
	 ·    the cd command is disabled
	 ·    the SHELL, ENV and PATH parameters can't be changed
	 ·    command names can't be specified with absolute or relative paths
	 ·    the -p option of the command built-in can't be used
	 ·    redirections that create files can't be used (i.e., >,  >|,  >>,
	      <>)

       A  shell	 is privileged if the -p option is used or if the real user-id
       or group-id does not match  the	effective  user-id  or	group-id  (see
       getuid(2), getgid(2)).  A privileged shell does not process $HOME/.pro‐
       file nor the ENV parameter (see below), instead the file /etc/suid_pro‐
       file  is processed.  Clearing the privileged option causes the shell to
       set its effective user-id (group-id) to its real user-id (group-id).

       If the basename of the name the shell is called	with  (i.e.,  argv[0])
       starts with - or if the -l option is used, the shell is assumed to be a
       login shell and the shell reads and executes the contents of  /etc/pro‐
       file, $HOME/.profile and $ENV if they exist and are readable.

       If  the	ENV parameter is set when the shell starts (or, in the case of
       login shells, after any profiles are processed), its value is subjected
       to  parameter,  command,	 arithmetic  and  tilde	 substitution  and the
       resulting file (if any) is read and executed.  If the ENV parameter  is
       not  set	 (and  not  null) the file $HOME/.kshrc is included (after the
       above mentioned substitutions have been performed).

       The exit status of the shell is 127 if the command  file	 specified  on
       the  command  line  could  not be opened, or non-zero if a fatal syntax
       error occurred during the execution of a script.	  In  the  absence  of
       fatal  errors, the exit status is that of the last command executed, or
       zero, if no command is executed.

   Command Syntax
       The shell begins parsing its input by breaking it into  words.	Words,
       which  are  sequences  of  characters, are delimited by unquoted white-
       space characters (space, tab and newline) or meta-characters (<, >,  |,
       ;,  &,  (  and  )).   Aside  from delimiting words, spaces and tabs are
       ignored, while newlines usually delimit commands.  The  meta-characters
       are  used  in building the following tokens: <, <&, <<, >, >&, >>, etc.
       are used to specify redirections (see Input/Output Redirection  below);
       |  is  used to create pipelines; |& is used to create co-processes (see
       Co-Processes below); ; is used to separate commands; & is used to  cre‐
       ate  asynchronous  pipelines; && and || are used to specify conditional
       execution; ;; is used in case statements; (( .. )) are used  in	arith‐
       metic expressions; and lastly, ( .. ) are used to create subshells.

       White-space  and meta-characters can be quoted individually using back‐
       slash (\), or in groups using double (") or single  (')	quotes.	  Note
       that  the  following characters are also treated specially by the shell
       and must be quoted if they are to represent themselves: \, ", ', #,  $,
       `,  ~,  {,  }, *, ? and [.  The first three of these are the above men‐
       tioned quoting characters (see Quoting below); #, if used at the begin‐
       ning of a word, introduces a comment — everything after the # up to the
       nearest newline is ignored; $ is used to introduce  parameter,  command
       and  arithmetic substitutions (see Substitution below); ` introduces an
       old-style command substitution (see Substitution	 below);  ~  begins  a
       directory expansion (see Tilde Expansion below); { and } delimit csh(1)
       style alternations (see Brace Expansion below); and, finally, *, ?  and
       [ are used in file name generation (see File Name Patterns below).

       As  words  and  tokens  are parsed, the shell builds commands, of which
       there are two basic types: simple-commands, typically programs that are
       executed,  and compound-commands, such as for and if statements, group‐
       ing constructs and function definitions.

       A simple-command consists of some combination of parameter  assignments
       (see  Parameters	 below),  input/output	redirections (see Input/Output
       Redirections below), and command words; the only	 restriction  is  that
       parameter  assignments  come  before  any  command  words.  The command
       words, if any, define the command that is to be executed and its	 argu‐
       ments.	The  command may be a shell built-in command, a function or an
       external command, i.e., a separate  executable  file  that  is  located
       using  the PATH parameter (see Command Execution below).	 Note that all
       command constructs have an exit status: for external commands, this  is
       related	to the status returned by wait(2) (if the command could not be
       found, the exit status is 127, if it could not be  executed,  the  exit
       status  is  126); the exit status of other command constructs (built-in
       commands, functions, compound-commands, pipelines, lists, etc.) are all
       well  defined  and are described where the construct is described.  The
       exit status of a command consisting only of  parameter  assignments  is
       that  of	 the  last command substitution performed during the parameter
       assignment or zero if there were no command substitutions.

       Commands can be chained together using the | token to  form  pipelines,
       in which the standard output of each command but the last is piped (see
       pipe(2)) to the standard input of the following command.	 The exit sta‐
       tus  of a pipeline is that of its last command.	A pipeline may be pre‐
       fixed by the ! reserved word which causes the exit status of the	 pipe‐
       line  to	 be  logically	complemented: if the original status was 0 the
       complemented status will be 1, and if the original status  was  not  0,
       then the complemented status will be 0.

       Lists  of commands can be created by separating pipelines by any of the
       following tokens: &&, ||, &, |& and ;.  The first two  are  for	condi‐
       tional execution: cmd1 && cmd2 executes cmd2 only if the exit status of
       cmd1 is zero; || is the opposite — cmd2 is executed only	 if  the  exit
       status  of  cmd1 is non-zero.  && and || have equal precedence which is
       higher than that of &, |& and ;, which also have equal precedence.  The
       &  token	 causes	 the  preceding command to be executed asynchronously,
       that is, the shell starts the command, but does not wait for it to com‐
       plete (the shell does keep track of the status of asynchronous commands
       — see Job Control below).  When an asynchronous command is started when
       job control is disabled (i.e., in most scripts), the command is started
       with signals INT and  QUIT  ignored  and	 with  input  redirected  from
       /dev/null  (however, redirections specified in the asynchronous command
       have precedence).  The |& operator starts a co-process which is special
       kind  of	 asynchronous  process	(see Co-Processes below).  Note that a
       command must follow the && and || operators, while a command  need  not
       follow &, |& and ;.  The exit status of a list is that of the last com‐
       mand executed, with the exception of asynchronous lists, for which  the
       exit status is 0.

       Compound	 commands  are	created	 using	the following reserved words —
       these words are only recognized if they are unquoted and	 if  they  are
       used  as	 the  first word of a command (i.e., they can't be preceded by
       parameter assignments or redirections):

			 case	else   function	  then	  !
			 do	esac   if	  time	  [[
			 done	fi     in	  until	  {
			 elif	for    select	  while	  }
       Note: Some shells (but not this one) execute control structure commands
       in  a  subshell	when  one  or more of their file descriptors are redi‐
       rected, so any environment changes inside them may fail.	 To be	porta‐
       ble,  the  exec	statement  should  be  used  instead  to redirect file
       descriptors before the control structure.

       In the following compound command descriptions, command lists  (denoted
       as  list)  that	are  followed  by reserved words must end with a semi-
       colon, a newline or a (syntactically correct) reserved word.  For exam‐
       ple,
	      { echo foo; echo bar; }
	      { echo foo; echo bar<newline>}
	      { { echo foo; echo bar; } }
       are all valid, but
	      { echo foo; echo bar }
       is not.

       ( list )
	      Execute  list  in	 a subshell.  There is no implicit way to pass
	      environment changes from a subshell back to its parent.

       { list }
	      Compound construct; list is executed, but	 not  in  a  subshell.
	      Note that { and } are reserved words, not meta-characters.

       case word in [ [(] pattern [| pattern] ... ) list ;; ] ... esac
	      The  case statement attempts to match word against the specified
	      patterns;	 the  list  associated	with  the  first  successfully
	      matched  pattern	is executed.  Patterns used in case statements
	      are the same as those used for file name	patterns  except  that
	      the  restrictions	 regarding . and / are dropped.	 Note that any
	      unquoted space before and after a pattern is stripped; any space
	      with  a  pattern must be quoted.	Both the word and the patterns
	      are subject to parameter, command, and  arithmetic  substitution
	      as well as tilde substitution.  For historical reasons, open and
	      close braces may be used instead of in and esac (e.g., case $foo
	      {	 *) echo bar; }).  The exit status of a case statement is that
	      of the executed list; if no list is executed, the exit status is
	      zero.

       for name [ in word ... term ] do list done
	      where  term  is  either  a newline or a ;.  For each word in the
	      specified word list, the parameter name is set to the  word  and
	      list is executed.	 If in is not used to specify a word list, the
	      positional parameters ("$1", "$2", etc.) are used instead.   For
	      historical reasons, open and close braces may be used instead of
	      do and done (e.g., for i; { echo $i; }).	The exit status	 of  a
	      for  statement is the last exit status of list; if list is never
	      executed, the exit status is zero.

       if list then list [elif list then list] ... [else list] fi
	      If the exit status of the first list is zero, the second list is
	      executed; otherwise the list following the elif, if any, is exe‐
	      cuted with similar consequences.	If all the lists following the
	      if  and  elifs  fail (i.e., exit with non-zero status), the list
	      following the else is executed.  The exit status of an if state‐
	      ment  is	that  of  non-conditional list that is executed; if no
	      non-conditional list is executed, the exit status is zero.

       select name [ in word ... term ] do list done
	      where term is either a newline or a  ;.	The  select  statement
	      provides	an automatic method of presenting the user with a menu
	      and selecting from it.  An  enumerated  list  of	the  specified
	      words  is	 printed on standard error, followed by a prompt (PS3,
	      normally `#? ').	A number corresponding to one of  the  enumer‐
	      ated  words is then read from standard input, name is set to the
	      selected word (or is unset if the selection is not valid), REPLY
	      is  set  to  what was read (leading/trailing space is stripped),
	      and list is executed.  If a blank line (i.e., zero or  more  IFS
	      characters) is entered, the menu is re-printed without executing
	      list.  When list completes, the enumerated list  is  printed  if
	      REPLY is null, the prompt is printed and so on.  This process is
	      continues until an end-of-file is read, an interrupt is received
	      or  a  break  statement is executed inside the loop.  If in word
	      ... is omitted, the positional parameters are used (i.e.,	 "$1",
	      "$2",  etc.).  For historical reasons, open and close braces may
	      be used instead of do and done (e.g., select i; { echo  $i;  }).
	      The  exit status of a select statement is zero if a break state‐
	      ment is used to exit the loop, non-zero otherwise.

       until list do list done
	      This works like while, except that the  body  is	executed  only
	      while the exit status of the first list is non-zero.

       while list do list done
	      A	 while is a prechecked loop.  Its body is executed as often as
	      the exit status of the first list is zero.  The exit status of a
	      while  statement is the last exit status of the list in the body
	      of the loop; if the body is not executed,	 the  exit  status  is
	      zero.

       function name { list }
	      Defines  the  function  name.   See  Functions below.  Note that
	      redirections specified after a function definition are performed
	      whenever the function is executed, not when the function defini‐
	      tion is executed.

       name () command
	      Mostly the same as function.  See Functions below.

       time [ -p ] [ pipeline ]
	      The time reserved word is described  in  the  Command  Execution
	      section.

       (( expression ))
	      The arithmetic expression expression is evaluated; equivalent to
	      let "expression".	 See Arithmetic Expressions and the  let  com‐
	      mand below.

       [[ expression ]]
	      Similar to the test and [ ... ] commands (described later), with
	      the following exceptions:
		·    Field splitting and file name  generation	are  not  per‐
		     formed on arguments.
		·    The  -a  (and) and -o (or) operators are replaced with &&
		     and ||, respectively.
		·    Operators (e.g., -f, =, !, etc.) must be unquoted.
		·    The second operand of != and = expressions	 are  patterns
		     (e.g., the comparison in
					[[ foobar = f*r ]]
		     succeeds).
		·    There  are two additional binary operators: < and > which
		     return true if their first string operand is  less	 than,
		     or	 greater  than,	 their	second string operand, respec‐
		     tively.
		·    The single argument form of  test,	 which	tests  if  the
		     argument  has  non-zero  length,  is not valid - explicit
		     operators must always be used, e.g., instead of
					      [ str ]
		     use
					   [[ -n str ]]
		·    Parameter, command and arithmetic substitutions are  per‐
		     formed  as	 expressions are evaluated and lazy expression
		     evaluation is used for the &&  and	 ||  operators.	  This
		     means that in the statement
				  [[ -r foo && $(< foo) = b*r ]]
		     the  $(<  foo)  is	 evaluated if and only if the file foo
		     exists and is readable.

   Quoting
       Quoting is used to prevent the shell from treating characters or	 words
       specially.   There  are	three  methods of quoting: First, \ quotes the
       following character, unless it is at the end of a line, in  which  case
       both  the  \  and the newline are stripped.  Second, a single quote (')
       quotes everything up to the next single quote (this  may	 span  lines).
       Third,  a double quote (") quotes all characters, except $, ` and \, up
       to the next unquoted double quote.  $ and ` inside double  quotes  have
       their  usual  meaning (i.e., parameter, command or arithmetic substitu‐
       tion) except no field splitting is carried out on the results  of  dou‐
       ble-quoted substitutions.  If a \ inside a double-quoted string is fol‐
       lowed by \, $, ` or ", it is replaced by the second character; if it is
       followed	 by a newline, both the \ and the newline are stripped; other‐
       wise, both the \ and the character following are unchanged.

       Note: An earlier	 version  of  ksh(1)  changed  the  interpretation  of
       sequences  of  the  form "...`...\"...`.."  according to whether or not
       POSIX mode was in effect.  In the current implementation, the backslash
       in  \"  is seen and removed by the outer "...", so the backslash is not
       seen by the inner `...`.

   Aliases
       There are two types of aliases:	normal	command	 aliases  and  tracked
       aliases.	  Command aliases are normally used as a short hand for a long
       or often used command.  The shell expands command aliases  (i.e.,  sub‐
       stitutes	 the alias name for its value) when it reads the first word of
       a command.  An  expanded	 alias	is  re-processed  to  check  for  more
       aliases.	 If a command alias ends in a space or tab, the following word
       is also checked for alias expansion.  The alias expansion process stops
       when  a word that is not an alias is found, when a quoted word is found
       or when an alias word that is currently being expanded is found.

       The following command aliases are defined automatically by the shell:
	      autoload='typeset -fu'
	      functions='typeset -f'
	      hash='alias -t'
	      history='fc -l'
	      integer='typeset -i'
	      local='typeset'
	      login='exec login'
	      nohup='nohup '
	      r='fc -e -'
	      stop='kill -STOP'
	      suspend='kill -STOP $$'
	      type='whence -v'

       Tracked aliases allow the shell to remember where it found a particular
       command.	  The  first  time  the shell does a path search for a command
       that is marked as a tracked alias, it saves the full path of  the  com‐
       mand.   The  next  time	the  command is executed, the shell checks the
       saved path to see that it is still valid, and if so,  avoids  repeating
       the path search.	 Tracked aliases can be listed and created using alias
       -t.  Note that changing the PATH parameter clears the saved  paths  for
       all  tracked  aliases.	If  the	 trackall  option is set (i.e., set -o
       trackall or set -h), the shell tracks all commands.  This option is set
       automatically for non-interactive shells.  For interactive shells, only
       the following commands are automatically tracked: cat, cc,  chmod,  cp,
       date, ed, emacs, grep, ls, mail, make, mv, pr, rm, sed, sh, vi and who.

   Substitution
       The first step the shell takes in executing a simple-command is to per‐
       form substitutions on the words of the command.	There are three	 kinds
       of  substitution: parameter, command and arithmetic.  Parameter substi‐
       tutions, which are described in detail in the next  section,  take  the
       form $name or ${...}; command substitutions take the form $(command) or
       `command`; and arithmetic substitutions take the form $((expression)).

       If a substitution appears outside of double quotes, the results of  the
       substitution are generally subject to word or field splitting according
       to the current value of the IFS parameter.  The IFS parameter specifies
       a  list	of characters which are used to break a string up into several
       words; any characters from the set space, tab and newline  that	appear
       in  the IFS characters are called IFS white space.  Sequences of one or
       more IFS white space characters, in combination with zero or  one  non-
       IFS white space characters delimit a field.  As a special case, leading
       and trailing IFS white space is stripped (i.e., no leading or  trailing
       empty  field is created by it); leading or trailing non-IFS white space
       does create an empty field.  Example: if IFS is set to `<space>:',  the
       sequence	 of  characters	 `<space>A<space>:<space><space>B::D' contains
       four fields: `A', `B', `' and `D'.  Note that if the IFS	 parameter  is
       set to the null string, no field splitting is done; if the parameter is
       unset, the default value of space, tab and newline is used.

       The results of substitution are, unless otherwise specified, also  sub‐
       ject  to brace expansion and file name expansion (see the relevant sec‐
       tions below).

       A command substitution is replaced by the output generated by the spec‐
       ified  command,	which  is run in a subshell.  For $(command) substitu‐
       tions, normal quoting rules are used when command is  parsed,  however,
       for the `command` form, a \ followed by any of $, ` or \ is stripped (a
       \ followed by any other character is unchanged).	 As a special case  in
       command	substitutions,	a command of the form < file is interpreted to
       mean substitute the contents of file ($(< foo) has the same  effect  as
       $(cat  foo),  but it is carried out more efficiently because no process
       is started).
       NOTE: $(command) expressions are currently parsed by finding the match‐
       ing  parenthesis,  regardless of quoting.  This will hopefully be fixed
       soon.

       Arithmetic substitutions are replaced by the  value  of	the  specified
       expression.   For  example, the command echo $((2+3*4)) prints 14.  See
       Arithmetic Expressions for a description of an expression.

   Parameters
       Parameters are shell variables; they can be assigned values  and	 their
       values  can  be	accessed  using a parameter substitution.  A parameter
       name is either one of the special single punctuation or digit character
       parameters  described  below, or a letter followed by zero or more let‐
       ters or digits (`_' counts as a letter).	 The later form can be treated
       as arrays by appending an array index of the form: [expr] where expr is
       an arithmetic expression.  Array indices are currently limited  to  the
       range 0 through 1023, inclusive.	 Parameter substitutions take the form
       $name, ${name} or ${name[expr]}, where name is a	 parameter  name.   If
       substitution  is	 performed  on a parameter (or an array parameter ele‐
       ment) that is not set, a null string is substituted unless the  nounset
       option  (set  -o	 nounset  or  set  -u)	is set, in which case an error
       occurs.

       Parameters can be assigned values in a  number  of  ways.   First,  the
       shell  implicitly  sets	some parameters like #, PWD, etc.; this is the
       only way the special single  character  parameters  are	set.   Second,
       parameters  are	imported  from	the  shell's  environment  at startup.
       Third, parameters can be assigned values on the command line, for exam‐
       ple,  `FOO=bar'	sets  the  parameter  FOO  to  bar; multiple parameter
       assignments can be given on a single command line and they can be  fol‐
       lowed  by a simple-command, in which case the assignments are in effect
       only for the  duration  of  the	command	 (such	assignments  are  also
       exported,  see  below  for  implications	 of this).  Note that both the
       parameter name and the = must be unquoted for the shell to recognize  a
       parameter  assignment.	The  fourth way of setting a parameter is with
       the export, readonly and typeset commands; see  their  descriptions  in
       the Command Execution section.  Fifth, for and select loops set parame‐
       ters as well as the getopts, read and set -A commands.  Lastly, parame‐
       ters  can  be  assigned values using assignment operators inside arith‐
       metic expressions (see  Arithmetic  Expressions	below)	or  using  the
       ${name=value} form of parameter substitution (see below).

       Parameters  with	 the export attribute (set using the export or typeset
       -x commands, or by parameter assignments followed by  simple  commands)
       are  put	 in  the  environment  (see environ(7)) of commands run by the
       shell as name=value pairs.  The order in which parameters appear in the
       environment  of a command is unspecified.  When the shell starts up, it
       extracts parameters and their values from its environment and automati‐
       cally sets the export attribute for those parameters.

       Modifiers can be applied to the ${name} form of parameter substitution:

       ${name:-word}
	      if  name	is set and not null, it is substituted, otherwise word
	      is substituted.

       ${name:+word}
	      if name is set and not  null,  word  is  substituted,  otherwise
	      nothing is substituted.

       ${name:=word}
	      if  name is set and not null, it is substituted, otherwise it is
	      assigned word and the resulting value of name is substituted.

       ${name:?word}
	      if name is set and not null, it is substituted,  otherwise  word
	      is  printed  on  standard error (preceded by name:) and an error
	      occurs (normally causing termination of a shell script, function
	      or  .-script).  If word is omitted the string `parameter null or
	      not set' is used instead.

       In the above modifiers, the : can be omitted, in which case the	condi‐
       tions  only  depend on name being set (as opposed to set and not null).
       If word is needed, parameter, command, arithmetic and  tilde  substitu‐
       tion are performed on it; if word is not needed, it is not evaluated.

       The following forms of parameter substitution can also be used:

       ${#name}
	      The  number  of  positional parameters if name is *, @ or is not
	      specified, or the length of the string value of parameter name.

       ${#name[*]}, ${#name[@]}
	      The number of elements in the array name.

       ${name#pattern}, ${name##pattern}
	      If pattern matches the beginning of the value of parameter name,
	      the  matched text is deleted from the result of substitution.  A
	      single # results in the shortest match, two #'s results  in  the
	      longest match.

       ${name%pattern}, ${name%%pattern}
	      Like  ${..#..}  substitution, but it deletes from the end of the
	      value.

       The following special parameters are implicitly set by  the  shell  and
       cannot be set directly using assignments:

       !      Process  id of the last background process started.  If no back‐
	      ground processes have been started, the parameter is not set.

       #      The number of positional parameters (i.e., $1, $2, etc.).

       $      The process ID of the shell, or the PID of the original shell if
	      it is a subshell.

       -      The  concatenation of the current single letter options (see set
	      command below for list of options).

       ?      The exit status of the last non-asynchronous  command  executed.
	      If  the  last  command  was killed by a signal, $? is set to 128
	      plus the signal number.

       0      The name the shell was invoked with (i.e., argv[0]), or the com‐
	      mand-name	 if it was invoked with the -c option and the command-
	      name was supplied, or the file argument, if it was supplied.  If
	      the posix option is not set, $0 is the name of the current func‐
	      tion or script.

       1 ... 9
	      The first nine positional parameters that were supplied  to  the
	      shell,  function or .-script.  Further positional parameters may
	      be accessed using ${number}.

       *      All positional parameters (except	 parameter  0),	 i.e.,	$1  $2
	      $3....   If  used outside of double quotes, parameters are sepa‐
	      rate words (which are subjected  to  word	 splitting);  if  used
	      within  double  quotes,  parameters  are	separated by the first
	      character of the IFS parameter (or the empty string  if  IFS  is
	      null).

       @      Same  as	$*,  unless  it is used inside double quotes, in which
	      case a separate word is generated for each positional  parameter
	      -	 if  there  are no positional parameters, no word is generated
	      ("$@" can be used to access arguments, verbatim, without	losing
	      null arguments or splitting arguments with spaces).

       The following parameters are set and/or used by the shell:

       _ (underscore)
	      When  an external command is executed by the shell, this parame‐
	      ter is set in the environment of the new process to the path  of
	      the  executed  command.	In  interactive use, this parameter is
	      also set in the parent shell to the last word  of	 the  previous
	      command.	 When  MAILPATH messages are evaluated, this parameter
	      contains the name of the file that changed (see MAILPATH parame‐
	      ter below).

       CDPATH Search  path for the cd built-in command.	 Works the same way as
	      PATH for those directories not beginning with / in cd  commands.
	      Note  that  if CDPATH is set and does not contain . nor an empty
	      path, the current directory is not searched.

       COLUMNS
	      Set to the number of columns on the terminal  or	window.	  Cur‐
	      rently  set  to  the  cols  value as reported by stty(1) if that
	      value is non-zero.  This parameter is used  by  the  interactive
	      line  editing  modes, and by select, set -o and kill -l commands
	      to format information in columns.

       EDITOR If the VISUAL parameter is not set, this parameter controls  the
	      command  line  editing  mode for interactive shells.  See VISUAL
	      parameter below for how this works.

       ENV    If this parameter is found to be set after any profile files are
	      executed,	 the  expanded value is used as a shell start-up file.
	      It typically contains function and alias definitions.

       ERRNO  Integer value of the shell's errno variable — indicates the rea‐
	      son the last system call failed.

	      Not implemented yet.

       EXECSHELL
	      If  set,	this parameter is assumed to contain the shell that is
	      to be used to execute commands that execve(2) fails  to  execute
	      and which do not start with a `#! shell' sequence.

       FCEDIT The editor used by the fc command (see below).

       FPATH  Like  PATH,  but	used when an undefined function is executed to
	      locate the file defining the function.  It is also searched when
	      a	 command  can't	 be found using PATH.  See Functions below for
	      more information.

       HISTFILE
	      The name of the file used to store history.  When	 assigned  to,
	      history  is loaded from the specified file.  Also, several invo‐
	      cations of the shell running on the same machine will share his‐
	      tory if their HISTFILE parameters all point at the same file.
	      NOTE:  if	 HISTFILE isn't set, no history file is used.  This is
	      different	  from	 the   original	  Korn	 shell,	  which	  uses
	      $HOME/.sh_history;  in future, pdksh may also use a default his‐
	      tory file.

       HISTSIZE
	      The number of commands normally stored for history, default 128.

       HOME   The default directory for the cd command and the	value  substi‐
	      tuted for an unqualified ~ (see Tilde Expansion below).

       IFS    Internal	field  separator,  used during substitution and by the
	      read command, to split values into distinct arguments;  normally
	      set  to  space,  tab  and	 newline.   See Substitution above for
	      details.
	      Note: this parameter is not imported from the  environment  when
	      the shell is started.

       KSH_VERSION
	      The version of shell and the date the version was created (read‐
	      only).  See also the version commands in Emacs Editing Mode  and
	      Vi Editing Mode sections, below.

       LINENO The  line	 number	 of  the function or shell script that is cur‐
	      rently being executed.

       LINES  Set to the number of lines on the terminal or window.

	      Not implemented yet.

       MAIL   If set, the user will be informed of the arrival of mail in  the
	      named file.  This parameter is ignored if the MAILPATH parameter
	      is set.

       MAILCHECK
	      How often, in seconds, the shell will  check  for	 mail  in  the
	      file(s)  specified  by MAIL or MAILPATH.	If 0, the shell checks
	      before each prompt.  The default is 600 (10 minutes).

       MAILPATH
	      A list of files to be checked for mail.  The list is colon sepa‐
	      rated,  and each file may be followed by a ? and a message to be
	      printed if new mail has arrived.	Command, parameter and	arith‐
	      metic substitution is performed on the message, and, during sub‐
	      stitution, the parameter $_ contains the name of the file.   The
	      default message is you have mail in $_.

       OLDPWD The  previous  working  directory.  Unset if cd has not success‐
	      fully changed directories since the shell	 started,  or  if  the
	      shell doesn't know where it is.

       OPTARG When  using  getopts,  it	 contains  the	argument  for a parsed
	      option, if it requires one.

       OPTIND The index of the last argument  processed	 when  using  getopts.
	      Assigning	 1  to	this parameter causes getopts to process argu‐
	      ments from the beginning the next time it is invoked.

       PATH   A colon separated list of directories  that  are	searched  when
	      looking  for  commands and .'d files.  An empty string resulting
	      from a leading or trailing colon,	 or  two  adjacent  colons  is
	      treated as a `.', the current directory.

       POSIXLY_CORRECT
	      If  set,	this  parameter causes the posix option to be enabled.
	      See POSIX Mode below.

       PPID   The process ID of the shell's parent (readonly).

       PS1    PS1 is the primary prompt for  interactive  shells.   Parameter,
	      command  and  arithmetic	substitutions  are performed, and ! is
	      replaced with the current command number (see fc command below).
	      A literal ! can be put in the prompt by placing !! in PS1.  Note
	      that since the command line editors try to figure out  how  long
	      the  prompt  is  (so  they  know	how  far  it is to edge of the
	      screen), escape codes in the prompt tend to mess things up.  You
	      can  tell	 the  shell  not  to  count certain sequences (such as
	      escape codes) by prefixing your prompt with a non-printing char‐
	      acter (such as control-A) followed by a carriage return and then
	      delimiting the escape codes with	this  non-printing  character.
	      If  you  don't  have  any non-printing characters, you're out of
	      luck...  BTW, don't blame me for this hack; it's in the original
	      ksh.  Default is `$ ' for non-root users, `# ' for root.

       PS2    Secondary	 prompt	 string, by default `> ', used when more input
	      is needed to complete a command.

       PS3    Prompt used by select statement when reading a  menu  selection.
	      Default is `#? '.

       PS4    Used  to prefix commands that are printed during execution trac‐
	      ing (see set -x command below).  Parameter, command  and	arith‐
	      metic substitutions are performed before it is printed.  Default
	      is `+ '.

       PWD    The current working directory.  Maybe unset  or  null  if	 shell
	      doesn't know where it is.

       RANDOM A	 simple	 random number generator.  Every time RANDOM is refer‐
	      enced, it is assigned the next number in a random number series.
	      The point in the series can be set by assigning a number to RAN‐
	      DOM (see rand(3)).

       REPLY  Default parameter for the read command if no  names  are	given.
	      Also  used  in select loops to store the value that is read from
	      standard input.

       SECONDS
	      The number of seconds since the shell started or, if the parame‐
	      ter  has	been  assigned an integer value, the number of seconds
	      since the assignment plus the value that was assigned.

       TMOUT  If set to a positive integer in an interactive shell, it	speci‐
	      fies the maximum number of seconds the shell will wait for input
	      after printing  the  primary  prompt  (PS1).   If	 the  time  is
	      exceeded, the shell exits.

       TMPDIR The  directory  shell  temporary	files are created in.  If this
	      parameter is not set, or does not contain the absolute path of a
	      writable directory, temporary files are created in /tmp.

       VISUAL If  set,	this  parameter controls the command line editing mode
	      for interactive shells.  If the last component of the path spec‐
	      ified  in this parameter contains the string vi, emacs or gmacs,
	      the vi, emacs or gmacs (Gosling emacs) editing mode is  enabled,
	      respectively.

   Tilde Expansion
       Tilde expansion, which is done in parallel with parameter substitution,
       is done on words starting with an unquoted ~.  The characters following
       the  tilde,  up to the first /, if any, are assumed to be a login name.
       If the login name is empty, + or -, the value of the HOME, PWD, or OLD‐
       PWD  parameter  is  substituted, respectively.  Otherwise, the password
       file is searched for the login name, and the tilde expression  is  sub‐
       stituted	 with  the  user's  home  directory.  If the login name is not
       found in the password file or if any quoting or parameter  substitution
       occurs in the login name, no substitution is performed.

       In  parameter  assignments  (those  preceding a simple-command or those
       occurring in the arguments of alias, export,  readonly,	and  typeset),
       tilde  expansion	 is done after any unquoted colon (:), and login names
       are also delimited by colons.

       The home directory of previously expanded login names  are  cached  and
       re-used.	  The  alias -d command may be used to list, change and add to
       this cache (e.g., `alias -d fac=/usr/local/facilities; cd ~fac/bin').

   Brace Expansion (alternation)
       Brace expressions, which take the form
	      prefix{str1,...,strN}suffix
       are expanded to N words, each of which is the concatenation of  prefix,
       stri  and  suffix  (e.g.,  `a{c,b{X,Y},d}e'  expands to four word: ace,
       abXe, abYe, and ade).  As noted in the example, brace  expressions  can
       be  nested  and	the resulting words are not sorted.  Brace expressions
       must contain an unquoted comma (,) for expansion to occur (i.e., {} and
       {foo}  are not expanded).  Brace expansion is carried out after parame‐
       ter substitution and before file name generation.

   File Name Patterns
       A file name pattern is a word containing one or more unquoted  ?	 or  *
       characters or [..] sequences.  Once brace expansion has been performed,
       the shell replaces file name patterns with the sorted names of all  the
       files  that  match  the	pattern	 (if  no files match, the word is left
       unchanged).  The pattern elements have the following meaning:

       ?      matches any single character.

       *      matches any sequence of characters.

       [..]   matches any of the characters inside the	brackets.   Ranges  of
	      characters can be specified by separating two characters by a -,
	      e.g., [a0-9] matches the letter a or any	digit.	 In  order  to
	      represent itself, a - must either be quoted or the first or last
	      character in the character list.	Similarly, a ] must be	quoted
	      or  the  first  character	 in the list if it is represent itself
	      instead of the end of the list.  Also, a	!   appearing  at  the
	      start  of the list has special meaning (see below), so to repre‐
	      sent itself it must be quoted or appear later in the list.

       [!..]  like [..], except it matches any character not inside the brack‐
	      ets.

       *(pattern| ... |pattern)
	      matches  any  string  of	characters  that  matches zero or more
	      occurrences of the specified  patterns.	Example:  the  pattern
	      *(foo|bar)  matches  the	strings `', `foo', `bar', `foobarfoo',
	      etc..

       +(pattern| ... |pattern)
	      matches any string of characters that matches one or more occur‐
	      rences   of   the	 specified  patterns.	Example:  the  pattern
	      +(foo|bar) matches the strings `foo', `bar', `foobarfoo', etc..

       ?(pattern| ... |pattern)
	      matches the empty string or a string that	 matches  one  of  the
	      specified	  patterns.   Example:	the  pattern  ?(foo|bar)  only
	      matches the strings `', `foo' and `bar'.

       @(pattern| ... |pattern)
	      matches a string that matches one	 of  the  specified  patterns.
	      Example:	the  pattern @(foo|bar) only matches the strings `foo'
	      and `bar'.

       !(pattern| ... |pattern)
	      matches any string that does not match one of the specified pat‐
	      terns.   Examples:  the  pattern	!(foo|bar) matches all strings
	      except `foo' and `bar'; the pattern !(*) matches no strings; the
	      pattern !(?)* matches all strings (think about it).

       Note that pdksh currently never matches . and .., but the original ksh,
       Bourne sh and bash do, so this may have to change (too bad).

       Note that none of the above pattern elements match either a period  (.)
       at the start of a file name or a slash (/), even if they are explicitly
       used in a [..] sequence; also, the names . and ..  are  never  matched,
       even by the pattern .*.

       If  the	markdirs  option is set, any directories that result from file
       name generation are marked with a trailing /.

       The POSIX character classes (i.e., [:class-name:] inside a [..] expres‐
       sion) are not yet implemented.

   Input/Output Redirection
       When  a	command	 is  executed, its standard input, standard output and
       standard error (file descriptors 0, 1 and 2, respectively) are normally
       inherited  from	the  shell.   Three exceptions to this are commands in
       pipelines, for which standard input and/or standard  output  are	 those
       set  up by the pipeline, asynchronous commands created when job control
       is disabled, for which standard input  is  initially  set  to  be  from
       /dev/null,  and	commands  for  which any of the following redirections
       have been specified:

       > file standard output is redirected to file.  If file does not	exist,
	      it  is  created;	if  it	does  exist, is a regular file and the
	      noclobber option is set, an error occurs, otherwise the file  is
	      truncated.   Note	 that  this  means the command cmd < foo > foo
	      will open foo for reading and then truncate it when it opens  it
	      for writing, before cmd gets a chance to actually read foo.

       >| file
	      same  as	>, except the file is truncated, even if the noclobber
	      option is set.

       >> file
	      same as >, except the file  an  existing	file  is  appended  to
	      instead  of being truncated.  Also, the file is opened in append
	      mode, so writes always go to the end of the file (see open(2)).

       < file standard input is redirected from	 file,	which  is  opened  for
	      reading.

       <> file
	      same as <, except the file is opened for reading and writing.

       << marker
	      after reading the command line containing this kind of redirect‐
	      ion (called a here document), the shell copies  lines  from  the
	      command  source  into  a	temporary  file	 until a line matching
	      marker is read.  When the command is executed, standard input is
	      redirected  from	the  temporary	file.	If  marker contains no
	      quoted characters, the contents of the temporary file  are  pro‐
	      cessed  as if enclosed in double quotes each time the command is
	      executed, so parameter, command and arithmetic substitutions are
	      performed,  along	 with  backslash  (\)  escapes for $, `, \ and
	      \newline.	 If multiple here documents are used on the same  com‐
	      mand line, they are saved in order.

       <<- marker
	      same  as	<<, except leading tabs are stripped from lines in the
	      here document.

       <& fd  standard input is duplicated from file descriptor fd.  fd can be
	      a	 single	 digit,	 indicating  the  number  of  an existing file
	      descriptor, the letter p, indicating the file descriptor associ‐
	      ated with the output of the current co-process, or the character
	      -, indicating standard input is to be closed.

       >& fd  same as <&, except the operation is done on standard output.

       In any of the above redirections, the file  descriptor  that  is	 redi‐
       rected  (i.e.,  standard	 input	or  standard output) can be explicitly
       given by preceding the redirection with	a  single  digit.   Parameter,
       command	and  arithmetic substitutions, tilde substitutions and (if the
       shell is interactive) file name generation are  all  performed  on  the
       file,  marker and fd arguments of redirections.	Note however, that the
       results of any file name generation are only used if a single  file  is
       matched;	 if  multiple  files  match, the word with the unexpanded file
       name generation characters is used.  Note that  in  restricted  shells,
       redirections which can create files cannot be used.

       For  simple-commands,  redirections may appear anywhere in the command,
       for compound-commands (if  statements,  etc.),  any  redirections  must
       appear at the end.  Redirections are processed after pipelines are cre‐
       ated and in the order they are given, so
	      cat /foo/bar 2>&1 > /dev/null | cat -n
       will print an error with a line number prepended to it.

   Arithmetic Expressions
       Integer arithmetic expressions can be used with the let command, inside
       $((..))	expressions,  inside  array  references (e.g., name[expr]), as
       numeric arguments to the test command, and as the value of  an  assign‐
       ment to an integer parameter.

       Expression  may contain alpha-numeric parameter identifiers, array ref‐
       erences, and integer constants and may be combined with the following C
       operators (listed and grouped in increasing order of precedence).

       Unary operators:
	      + - ! ~ ++ --

       Binary operators:
	      ,
	      = *= /= %= += -= <<= >>= &= ^= |=
	      ||
	      &&
	      |
	      ^
	      &
	      == !=
	      < <= >= >
	      << >>
	      + -
	      * / %

       Ternary operator:
	      ?: (precedence is immediately higher than assignment)

       Grouping operators:
	      ( )

       Integer constants may be specified with arbitrary bases using the nota‐
       tion base#number, where base is a decimal integer specifying the	 base,
       and number is a number in the specified base.

       The operators are evaluated as follows:

	      unary +
		     result is the argument (included for completeness).

	      unary -
		     negation.

	      !	     logical  not;  the	 result is 1 if argument is zero, 0 if
		     not.

	      ~	     arithmetic (bit-wise) not.

	      ++     increment; must be applied to a parameter (not a  literal
		     or other expression) - the parameter is incremented by 1.
		     When used as a prefix operator, the result is the	incre‐
		     mented  value  of	the  parameter, when used as a postfix
		     operator, the result is the original value of the parame‐
		     ter.

	      --     similar to ++, except the parameter is decremented by 1.

	      ,	     separates	two arithmetic expressions; the left hand side
		     is evaluated first, then the right.  The result is	 value
		     of the expression on the right hand side.

	      =	     assignment;  variable  on the left is set to the value on
		     the right.

	      *= /= %= += -= <<= >>= &= ^= |=
		     assignment operators; <var> <op>= <expr> is the  same  as
		     <var> = <var> <op> ( <expr> ).

	      ||     logical  or;  the	result is 1 if either argument is non-
		     zero, 0 if not.  The right argument is evaluated only  if
		     the left argument is zero.

	      &&     logical  and;  the result is 1 if both arguments are non-
		     zero, 0 if not.  The right argument is evaluated only  if
		     the left argument is non-zero.

	      |	     arithmetic (bit-wise) or.

	      ^	     arithmetic (bit-wise) exclusive-or.

	      &	     arithmetic (bit-wise) and.

	      ==     equal;  the result is 1 if both arguments are equal, 0 if
		     not.

	      !=     not equal; the result is 0 if both arguments are equal, 1
		     if not.

	      <	     less  than;  the result is 1 if the left argument is less
		     than the right, 0 if not.

	      <= >= >
		     less than or equal, greater than or equal, greater	 than.
		     See <.

	      << >>  shift  left (right); the result is the left argument with
		     its bits shifted left (right) by the amount given in  the
		     right argument.

	      + - * /
		     addition, subtraction, multiplication, and division.

	      %	     remainder; the result is the remainder of the division of
		     the left argument by the right.  The sign of  the	result
		     is unspecified if either argument is negative.

	      <arg1> ? <arg2> : <arg3>
		     if	 <arg1>	 is  non-zero, the result is <arg2>, otherwise
		     <arg3>.

   Co-Processes
       A co-process, which is a pipeline created with the |& operator,	is  an
       asynchronous  process that the shell can both write to (using print -p)
       and read from (using read -p).  The input and output of the  co-process
       can  also  be manipulated using >&p and <&p redirections, respectively.
       Once a co-process has been started, another can't be started until  the
       co-process  exits,  or  until  the co-process input has been redirected
       using an exec n>&p redirection.	If a co-process's input is  redirected
       in  this	 way,  the next co-process to be started will share the output
       with the first co-process, unless the output of the initial  co-process
       has been redirected using an exec n<&p redirection.

       Some notes concerning co-processes:
	 ·    the  only	 way  to close the co-process input (so the co-process
	      reads an end-of-file) is to redirect the	input  to  a  numbered
	      file  descriptor and then close that file descriptor (e.g., exec
	      3>&p;exec 3>&-).
	 ·    in order for co-processes to share a common  output,  the	 shell
	      must keep the write portion of the output pipe open.  This means
	      that end of file will not be  detected  until  all  co-processes
	      sharing  the  co-process output have exited (when they all exit,
	      the shell closes its copy of the pipe).  This can be avoided  by
	      redirecting  the	output	to a numbered file descriptor (as this
	      also causes the shell to close its copy).	 Note that this behav‐
	      iour  is	slightly  different from the original Korn shell which
	      closes its copy of the write portion of the co-processes' output
	      when  the	 most recently started co-process (instead of when all
	      sharing co-processes) exits.
	 ·    print -p will ignore SIGPIPE signals during writes if the signal
	      is not being trapped or ignored; the same is not true if the co-
	      process input has been duplicated to another file descriptor and
	      print -un is used.

   Functions
       Functions  are  defined using either Korn shell function name syntax or
       the Bourne/POSIX shell name() syntax  (see  below  for  the  difference
       between	the two forms).	 Functions are like .-scripts in that they are
       executed in the current environment, however, unlike  .-scripts,	 shell
       arguments  (i.e.,  positional  parameters,  $1, etc.) are never visible
       inside them.  When the shell is determining the location of a  command,
       functions are searched after special built-in commands, and before reg‐
       ular and non-regular built-ins, and before the PATH is searched.

       An existing function may be deleted using unset	-f  function-name.   A
       list  of	 functions  can	 be obtained using typeset +f and the function
       definitions can be listed using typeset	-f.   autoload	(which	is  an
       alias  for typeset -fu) may be used to create undefined functions; when
       an undefined function is executed, the shell searches the  path	speci‐
       fied  in the FPATH parameter for a file with the same name as the func‐
       tion, which, if found is read and executed.   If	 after	executing  the
       file,  the  named function is found to be defined, the function is exe‐
       cuted, otherwise, the normal command search  is	continued  (i.e.,  the
       shell searches the regular built-in command table and PATH).  Note that
       if a command is not found using PATH, an attempt is made to autoload  a
       function	 using	FPATH (this is an undocumented feature of the original
       Korn shell).

       Functions can have two attributes, trace and export, which can  be  set
       with typeset -ft and typeset -fx, respectively.	When a traced function
       is executed, the shell's xtrace option is turned on for	the  functions
       duration,  otherwise  the  xtrace  option  is  turned  off.  The export
       attribute of functions is currently not used.   In  the	original  Korn
       shell,  exported	 functions  are visible to shell scripts that are exe‐
       cuted.

       Since functions are executed in the current shell environment,  parame‐
       ter  assignments	 made  inside functions are visible after the function
       completes.  If this is not the desired effect, the typeset command  can
       be  used inside a function to create a local parameter.	Note that spe‐
       cial parameters (e.g., $$, $!) can't be scoped in this way.

       The exit status of a function is that of the last command  executed  in
       the  function.	A function can be made to finish immediately using the
       return command; this may also be used to explicitly  specify  the  exit
       status.

       Functions  defined  with the function reserved word are treated differ‐
       ently in the following ways from functions defined with	the  ()	 nota‐
       tion:
	 ·    the  $0  parameter  is  set to the name of the function (Bourne-
	      style functions leave $0 untouched).
	 ·    parameter assignments preceding function calls are not  kept  in
	      the  shell  environment  (executing  Bourne-style functions will
	      keep assignments).
	 ·    OPTIND is saved/reset and restored on entry and  exit  from  the
	      function so getopts can be used properly both inside and outside
	      the function (Bourne-style functions leave OPTIND untouched,  so
	      using  getopts  inside  a function interferes with using getopts
	      outside the function).  In the future, the following differences
	      will also be added:
	 ·    A	 separate trap/signal environment will be used during the exe‐
	      cution of functions.  This will mean that	 traps	set  inside  a
	      function	will not affect the shell's traps and signals that are
	      not ignored in the shell (but may be trapped)  will  have	 their
	      default effect in a function.
	 ·    The  EXIT trap, if set in a function, will be executed after the
	      function returns.

   POSIX Mode
       The shell is intended to be POSIX compliant, however,  in  some	cases,
       POSIX behaviour is contrary either to the original Korn shell behaviour
       or to user convenience.	How the shell behaves in these cases is deter‐
       mined  by  the  state of the posix option (set -o posix) — if it is on,
       the POSIX behaviour is followed, otherwise it is not.  The posix option
       is  set	automatically when the shell starts up if the environment con‐
       tains the POSIXLY_CORRECT parameter.  (The shell can also  be  compiled
       so  that	 it  is	 in POSIX mode by default, however this is usually not
       desirable).

       The following is a list of things that are affected by the state of the
       posix option:
	 ·    kill  -l	output:	 in  posix mode, signal names are listed one a
	      single line;  in	non-posix  mode,  signal  numbers,  names  and
	      descriptions  are	 printed  in columns.  In future, a new option
	      (-v perhaps) will be added to distinguish the two behaviours.
	 ·    fg exit status: in posix mode, the exit status is 0 if no errors
	      occur;  in  non-posix  mode, the exit status is that of the last
	      foregrounded job.
	 ·    eval exit status: if eval gets to see an	empty  command	(e.g.,
	      eval  "`false`"),	 its  exit status in posix mode will be 0.  In
	      non-posix mode, it will be the exit status of the	 last  command
	      substitution that was done in the processing of the arguments to
	      eval (or 0 if there were no command substitutions).
	 ·    getopts: in posix mode, options must start with  a  -;  in  non-
	      posix mode, options can start with either - or +.
	 ·    brace  expansion	(also  known  as  alternation): in posix mode,
	      brace expansion is disabled; in non-posix mode, brace  expansion
	      enabled.	Note that set -o posix (or setting the POSIXLY_CORRECT
	      parameter) automatically turns the braceexpand option off,  how‐
	      ever it can be explicitly turned on later.
	 ·    set  -: in posix mode, this does not clear the verbose or xtrace
	      options; in non-posix mode, it does.
	 ·    set exit status: in posix mode, the exit status of set is	 0  if
	      there  are no errors; in non-posix mode, the exit status is that
	      of any command substitutions performed  in  generating  the  set
	      command.	 For  example,	`set  -- `false`; echo $?' prints 0 in
	      posix mode, 1 in non-posix mode.	This construct is used in most
	      shell scripts that use the old getopt(1) command.
	 ·    argument	expansion of alias, export, readonly, and typeset com‐
	      mands: in posix mode, normal argument expansion  done;  in  non-
	      posix  mode,  field splitting, file globing, brace expansion and
	      (normal) tilde expansion are turned off,	and  assignment	 tilde
	      expansion is turned on.
	 ·    signal specification: in posix mode, signals can be specified as
	      digits only if signal numbers match POSIX values	(i.e.,	HUP=1,
	      INT=2,  QUIT=3,  ABRT=6,	KILL=9, ALRM=14, and TERM=15); in non-
	      posix mode, signals can be always digits.
	 ·    alias expansion: in posix mode, alias expansion is only  carried
	      out  when reading command words; in non-posix mode, alias expan‐
	      sion is carried out on any word following an alias that ended in
	      a space.	For example, the following for loop
	      alias a='for ' i='j'
	      a i in 1 2; do echo i=$i j=$j; done
       uses parameter i in posix mode, j in non-posix mode.
	 ·    test:  in posix mode, the expression "-t" (preceded by some num‐
	      ber of "!" arguments) is always true as it is a non-zero	length
	      string;  in  non-posix  mode, it tests if file descriptor 1 is a
	      tty (i.e., the fd argument to the -t test may be	left  out  and
	      defaults to 1).

   Command Execution
       After  evaluation of command line arguments, redirections and parameter
       assignments, the type of command is determined: a special  built-in,  a
       function,  a  regular  built-in	or the name of a file to execute found
       using the PATH parameter.  The checks are  made	in  the	 above	order.
       Special	built-in  commands differ from other commands in that the PATH
       parameter is not used to find them, an error during their execution can
       cause  a	 non-interactive  shell to exit and parameter assignments that
       are specified before the command are kept after the command  completes.
       Just to confuse things, if the posix option is turned off (see set com‐
       mand below) some special commands are very special  in  that  no	 field
       splitting,  file	 globing,  brace expansion nor tilde expansion is per‐
       formed on arguments that look like assignments.	Regular built-in  com‐
       mands are different only in that the PATH parameter is not used to find
       them.

       The original ksh and POSIX differ somewhat in which commands  are  con‐
       sidered special or regular:

       POSIX special commands

	      .		 continue   exit       return	  trap
	      :		 eval	    export     set	  unset
	      break	 exec	    readonly   shift

       Additional ksh special commands

	      builtin	 times	    typeset

       Very special commands (non-posix mode)

	      alias	 readonly   set	       typeset

       POSIX regular commands

	      alias	 command    fg	       kill	  umask

	      bg	 false	    getopts    read	  unalias
	      cd	 fc	    jobs       true	  wait

       Additional ksh regular commands

	      [		 let	    pwd	       ulimit
	      echo	 print	    test       whence

       In  the	future, the additional ksh special and regular commands may be
       treated differently from the POSIX special and regular commands.

       Once the type of the command has	 been  determined,  any	 command  line
       parameter  assignments  are  performed and exported for the duration of
       the command.

       The following describes the special and regular built-in commands:

       . file [arg1 ...]
	      Execute the commands in file in the  current  environment.   The
	      file  is	searched for in the directories of PATH.  If arguments
	      are given, the positional parameters may be used to access  them
	      while  file  is  being executed.	If no arguments are given, the
	      positional parameters are those of the environment  the  command
	      is used in.

       : [ ... ]
	      The null command.	 Exit status is set to zero.

       alias [ -d | ±t [-r] ] [±px] [±] [name1[=value1] ...]
	      Without  arguments, alias lists all aliases.  For any name with‐
	      out a value, the existing alias is  listed.   Any	 name  with  a
	      value defines an alias (see Aliases above).

	      When  listing  aliases,  one  of	two formats is used: normally,
	      aliases are listed as name=value,	 where	value  is  quoted;  if
	      options were preceded with + or a lone + is given on the command
	      line, only name is printed.  In addition, if the	-p  option  is
	      used, each alias is prefixed with the string "alias ".

	      The -x option sets (+x clears) the export attribute of an alias,
	      or, if no names are given, lists the  aliases  with  the	export
	      attribute (exporting an alias has no affect).

	      The   -t	option	indicates  that	 tracked  aliases  are	to  be
	      listed/set (values specified on the command line are ignored for
	      tracked  aliases).   The	-r  option  indicates that all tracked
	      aliases are to be reset.

	      The -d causes directory aliases, which are used in tilde	expan‐
	      sion, to be listed or set (see Tilde Expansion above).

       bg [job ...]
	      Resume  the  specified  stopped job(s) in the background.	 If no
	      jobs are specified, %+ is assumed.  This command is only	avail‐
	      able  on	systems	 which	support	 job control.  See Job Control
	      below for more information.

       bind [-l] [-m] [key[=editing-command] ...]
	      Set  or  view  the  current  emacs  command  editing  key	 bind‐
	      ings/macros.   See  Emacs	 Editing  Mode	below  for  a complete
	      description.

       break [level]
	      break exits the levelth inner most for, select, until, or	 while
	      loop.  level defaults to 1.

       builtin command [arg1 ...]
	      Execute the built-in command command.

       cd [-LP] [dir]
	      Set  the	working	 directory to dir.  If the parameter CDPATH is
	      set, it lists directories to search in for dir.  An empty	 entry
	      in the CDPATH entry means the current directory.	If a non-empty
	      directory from CDPATH  is	 used,	the  resulting	full  path  is
	      printed  to standard output.  If dir is missing, the home direc‐
	      tory $HOME is used.  If dir is -, the previous working directory
	      is  used (see OLDPWD parameter).	If -L option (logical path) is
	      used or if the physical option (see  set	command	 below)	 isn't
	      set,  references	to .. in dir are relative to the path used get
	      to the directory.	 If -P option (physical path) is  used	or  if
	      the  physical  option  is	 set, .. is relative to the filesystem
	      directory tree.  The PWD and OLDPWD parameters  are  updated  to
	      reflect the current and old wording directory, respectively.

       cd [-LP] old new
	      The  string new is substituted for old in the current directory,
	      and the shell attempts to change to the new directory.

       command [-pvV] cmd [arg1 ...]
	      If neither the -v nor -V options	are  given,  cmd  is  executed
	      exactly  as  if  the  command  had  not been specified, with two
	      exceptions: first, cmd cannot be a shell function,  and  second,
	      special  built-in	 commands  lose their specialness (i.e., redi‐
	      rection and utility errors do not cause the shell to  exit,  and
	      command  assignments  are	 not  permanent).  If the -p option is
	      given, a default search path is  used  instead  of  the  current
	      value  of	 PATH  (the actual value of the default path is system
	      dependent: on POSIXish systems, it is the value returned by
				      getconf CS_PATH
	      ).

	      If the -v option is given, instead of executing cmd, information
	      about  what would be executed is given (and the same is done for
	      arg1 ...): for special and regular built-in commands  and	 func‐
	      tions,  their  names  are simply printed, for aliases, a command
	      that defines them is printed, and for commands found by  search‐
	      ing the PATH parameter, the full path of the command is printed.
	      If no command is found, (i.e., the path search  fails),  nothing
	      is  printed  and	command	 exits with a non-zero status.	The -V
	      option is like the -v option, except it is more verbose.

       continue [levels]
	      continue jumps to the beginning of the levelth inner  most  for,
	      select, until, or while loop.  level defaults to 1.

       echo [-neE] [arg ...]
	      Prints  its  arguments  (separated by spaces) followed by a new‐
	      line, to standard out.  The newline is suppressed if any of  the
	      arguments	 contain the backslash sequence \c.  See print command
	      below for a list of other backslash sequences  that  are	recog‐
	      nized.

	      The  options  are	 provided  for	compatibility  with  BSD shell
	      scripts: -n suppresses the trailing newline,  -e	enables	 back‐
	      slash interpretation (a no-op, since this is normally done), and
	      -E suppresses backslash interpretation.

       eval command ...
	      The arguments are concatenated (with  spaces  between  them)  to
	      form a single string which the shell then parses and executes in
	      the current environment.

       exec [command [arg ...]]
	      The command is executed without  forking,	 replacing  the	 shell
	      process.

	      If  no  arguments are given, any IO redirection is permanent and
	      the shell is not replaced.  Any file descriptors greater than  2
	      which are opened or dup(2)-ed in this way are not made available
	      to other executed commands (i.e., commands that are not built-in
	      to the shell).  Note that the Bourne shell differs here: it does
	      pass these file descriptors on.

       exit [status]
	      The shell exits with the specified exit status.	If  status  is
	      not  specified,  the  exit  status is the current value of the ?
	      parameter.

       export [-p] [parameter[=value]] ...
	      Sets the export attribute of  the	 named	parameters.   Exported
	      parameters  are  passed in the environment to executed commands.
	      If values are specified, the named parameters also assigned.

	      If no parameters are specified, the names of all parameters with
	      the  export  attribute  are  printed one per line, unless the -p
	      option is used, in  which	 case  export  commands	 defining  all
	      exported parameters, including their values, are printed.

       false  A command that exits with a non-zero status.

       fc [-e editor | -l [-n]] [-r] [first [last]]
	      first  and  last select commands from the history.  Commands can
	      be selected by history number, or a string specifying  the  most
	      recent  command  starting with that string.  The -l option lists
	      the command on stdout, and -n inhibits the default command  num‐
	      bers.   The  -r  option reverses the order of the list.  Without
	      -l, the selected commands are edited  by	the  editor  specified
	      with  the -e option, or if no -e is specified, the editor speci‐
	      fied by the FCEDIT parameter (if	this  parameter	 is  not  set,
	      /bin/ed is used), and then executed by the shell.

       fc [-e - | -s] [-g] [old=new] [prefix]
	      Re-execute   the	selected  command  (the	 previous  command  by
	      default) after performing the optional substitution of old  with
	      new.   If	 -g  is specified, all occurrences of old are replaced
	      with new.	 This command is usually accessed with the  predefined
	      alias r='fc -e -'.

       fg [job ...]
	      Resume  the  specified job(s) in the foreground.	If no jobs are
	      specified, %+ is assumed.	 This command  is  only	 available  on
	      systems  which  support  job control.  See Job Control below for
	      more information.

       getopts optstring name [arg ...]
	      getopts is used by shell procedures to parse the specified argu‐
	      ments  (or positional parameters, if no arguments are given) and
	      to check for legal options.  optstring contains the option  let‐
	      ters that getopts is to recognize.  If a letter is followed by a
	      colon, the option is expected to have an argument.  Options that
	      do  not  take arguments may be grouped in a single argument.  If
	      an option takes an argument and the option character is not  the
	      last  character of the argument it is found in, the remainder of
	      the argument is taken to be the  option's	 argument,  otherwise,
	      the next argument is the option's argument.

	      Each  time  getopts is invoked, it places the next option in the
	      shell parameter name and the index of the next  argument	to  be
	      processed	 in  the  shell	 parameter  OPTIND.  If the option was
	      introduced with a +, the option placed in name is prefixed  with
	      a	 +.  When an option requires an argument, getopts places it in
	      the shell parameter OPTARG.  When an illegal option or a missing
	      option  argument	is  encountered	 a question mark or a colon is
	      placed in name (indicating an illegal option  or	missing	 argu‐
	      ment,  respectively)  and	 OPTARG is set to the option character
	      that caused the problem.	An error message is  also  printed  to
	      standard error if optstring does not begin with a colon.

	      When the end of the options is encountered, getopts exits with a
	      non-zero exit status.  Options end  at  the  first  (non-option)
	      argument	that does not start with a -, or when a -- argument is
	      encountered.

	      Option parsing can be reset by setting OPTIND to 1 (this is done
	      automatically  whenever  the  shell  or  a  shell	 procedure  is
	      invoked).

	      Warning: Changing the value of the shell parameter OPTIND	 to  a
	      value other than 1, or parsing different sets of arguments with‐
	      out resetting OPTIND may lead to unexpected results.

       hash [-r] [name ...]
	      Without arguments, any hashed executable command	pathnames  are
	      listed.	The -r option causes all hashed commands to be removed
	      from the hash table.  Each name is searched as  if  it  where  a
	      command  name and added to the hash table if it is an executable
	      command.

       jobs [-lpn] [job ...]
	      Display information about the specified jobs;  if	 no  jobs  are
	      specified,  all jobs are displayed.  The -n option causes infor‐
	      mation to be displayed only for jobs  that  have	changed	 state
	      since  the  last	notification.	If  the -l option is used, the
	      process-id of each process in a job  is  also  listed.   The  -p
	      option  causes only the process group of each job to be printed.
	      See Job Control below for the format of job  and	the  displayed
	      job.

       kill [-s signame | -signum | -signame ] { job | pid | -pgrp } ...
	      Send the specified signal to the specified jobs, process ids, or
	      process groups.  If no signal is specified, the signal  TERM  is
	      sent.   If  a  job is specified, the signal is sent to the job's
	      process group.  See Job Control below for the format of job.

       kill -l [exit-status ...]
	      Print the name of the signal that killed a process which	exited
	      with  the	 specified  exit-statuses.  If no arguments are speci‐
	      fied, a list of all the  signals,	 their	numbers	 and  a	 short
	      description of them are printed.

       let [expression ...]
	      Each  expression is evaluated, see Arithmetic Expressions above.
	      If all expressions are successfully evaluated, the  exit	status
	      is  0  (1)  if the last expression evaluated to non-zero (zero).
	      If an error occurs  during  the  parsing	or  evaluation	of  an
	      expression,  the	exit  status is greater than 1.	 Since expres‐
	      sions may need to be quoted, (( expr )) is syntactic  sugar  for
	      let "expr".

       print [-nprsun | -R [-en]] [argument ...]
	      Print  prints its arguments on the standard output, separated by
	      spaces, and terminated with a newline.  The -n option suppresses
	      the  newline.   By  default,  certain  C escapes are translated.
	      These include \b, \f, \n, \r, \t, \v, and \0### (# is  an	 octal
	      digit, of which there may be 0 to 3).  \c is equivalent to using
	      the -n option.  \ expansion may be inhibited with the -r option.
	      The  -s  option  prints  to the history file instead of standard
	      output, the -u option prints to file descriptor n (n defaults to
	      1	 if  omitted), and the -p option prints to the co-process (see
	      Co-Processes above).

	      The -R option is used to emulate, to some degree, the  BSD  echo
	      command, which does not process \ sequences unless the -e option
	      is given.	 As above, the -n option suppresses the trailing  new‐
	      line.

       pwd [-LP]
	      Print the present working directory.  If -L option is used or if
	      the physical option (see set command below) isn't set, the logi‐
	      cal  path	 is  printed (i.e., the path used to cd to the current
	      directory).  If -P option (physical path)	 is  used  or  if  the
	      physical	option is set, the path determined from the filesystem
	      (by following ..	directories to the root directory) is printed.

       read [-prsun] [parameter ...]
	      Reads a line of input from standard  input,  separate  the  line
	      into  fields  using  the IFS parameter (see Substitution above),
	      and assign each field to the specified parameters.  If there are
	      more  parameters	than  fields,  the extra parameters are set to
	      null, or alternatively, if there are more	 fields	 than  parame‐
	      ters,  the  last	parameter  is  assigned	 the  remaining fields
	      (inclusive of any separating  spaces).   If  no  parameters  are
	      specified,  the REPLY parameter is used.	If the input line ends
	      in a backslash and the -r option was not used, the backslash and
	      newline  are  stripped  and  more input is read.	If no input is
	      read, read exits with a non-zero status.

	      The first parameter may  have  a	question  mark	and  a	string
	      appended	to  it,	 in  which case the string is used as a prompt
	      (printed to standard error before any  input  is	read)  if  the
	      input is a tty (e.g., read nfoo?'number of foos: ').

	      The -un and -p options cause input to be read from file descrip‐
	      tor n or the current co-process (see Co-Processes above for com‐
	      ments  on	 this), respectively.  If the -s option is used, input
	      is saved to the history file.

       readonly [-p] [parameter[=value]] ...
	      Sets the readonly attribute of the named parameters.  If	values
	      are  given,  parameters  are  set	 to  them  before  setting the
	      attribute.  Once a parameter is  made  readonly,	it  cannot  be
	      unset and its value cannot be changed.

	      If no parameters are specified, the names of all parameters with
	      the readonly attribute are printed one per line, unless  the  -p
	      option  is  used,	 in  which case readonly commands defining all
	      readonly parameters, including their values, are printed.

       return [status]
	      Returns from a function or . script, with	 exit  status  status.
	      If no status is given, the exit status of the last executed com‐
	      mand is used.  If used outside of a function or . script, it has
	      the  same	 effect	 as exit.  Note that pdksh treats both profile
	      and $ENV files as . scripts, while the original Korn shell  only
	      treats profiles as . scripts.

       set [±abCefhkmnpsuvxX] [±o [option]] [±A name] [--] [arg ...]
	      The  set	command	 can  be  used	to  set (-) or clear (+) shell
	      options, set the positional parameters, or set an array  parame‐
	      ter.   Options  can be changed using the ±o option syntax, where
	      option is the long name of an option, or using the ±letter  syn‐
	      tax,  where  letter  is the option's single letter name (not all
	      options have a single letter name).  The following  table	 lists
	      both  option letters (if they exist) and long names along with a
	      description of what the option does.

	       -A				Sets the elements of the array
						parameter  name to arg ...; If
						-A is used, the array is reset
						(i.e.,	emptied)  first; if +A
						is used, the first N  elements
						are set (where N is the number
						of args), the  rest  are  left
						untouched.
	       -a	  allexport		all new parameters are created
						with the export attribute
	       -b	  notify		Print  job  notification  mes‐
						sages  asynchronously, instead
						of  just  before  the  prompt.
						Only  used  if	job control is
						enabled (-m).
	       -C	  noclobber		Prevent	 >  redirection	  from
						overwriting existing files (>|
						must be used to force an over‐
						write).
	       -e	  errexit		Exit  (after executing the ERR
						trap)  as  soon	 as  an	 error
						occurs	 or  a	command	 fails
						(i.e., exits with  a  non-zero
						status).   This does not apply
						to commands whose exit	status
						is   explicitly	 tested	 by  a
						shell construct	 such  as  if,
						until,	while, && or || state‐
						ments.
	       -f	  noglob		Do not expand file  name  pat‐
						terns.
	       -h	  trackall		Create tracked aliases for all
						executed commands (see Aliases
						above).	  On  by  default  for
						non-interactive shells.
	       -i	  interactive		Enable interactive mode - this
						can only be set/unset when the
						shell is invoked.

	       -k	  keyword		Parameter assignments are rec‐
						ognized anywhere in a command.
	       -l	  login			The  shell  is a login shell -
						this  can  only	 be  set/unset
						when the shell is invoked (see
						Shell Startup above).
	       -m	  monitor		Enable	job  control  (default
						for interactive shells).
	       -n	  noexec		Do  not execute any commands -
						useful for checking the syntax
						of  scripts (ignored if inter‐
						active).
	       -p	  privileged		Set automatically if, when the
						shell  starts, the real uid or
						gid does not match the	effec‐
						tive uid or gid, respectively.
						See Shell Startup above for  a
						description   of   what	  this
						means.
	       -r	  restricted		Enable restricted mode —  this
						option	can  only be used when
						the  shell  is	invoked.   See
						Shell	Startup	 above	for  a
						description   of   what	  this
						means.
	       -s	  stdin			If  used  when	the  shell  is
						invoked,  commands  are	  read
						from   standard	  input.   Set
						automatically if the shell  is
						invoked with no arguments.

						When  -s  is  used  in the set
						command, it causes the	speci‐
						fied  arguments	 to  be sorted
						before assigning them  to  the
						positional  parameters	(or to
						array name, if -A is used).
	       -u	  nounset		Referencing of an unset param‐
						eter  is  treated as an error,
						unless one of the -,  +	 or  =
						modifiers is used.
	       -v	  verbose		Write  shell input to standard
						error as it is read.
	       -x	  xtrace		Print commands	and  parameter
						assignments when they are exe‐
						cuted, preceded by  the	 value
						of PS4.
	       -X	  markdirs		Mark directories with a trail‐
						ing / during file name genera‐
						tion.
			  bgnice		Background  jobs  are run with
						lower priority.
			  braceexpand		Enable brace  expansion	 (aka,
						alternation).
			  emacs			Enable	BRL emacs-like command
						line   editing	  (interactive
						shells	only); see Emacs Edit‐
						ing Mode.
			  emacs-usemeta		In emacs command-line editing,
						use  the  8th bit as meta (^[)
						prefix.	 This is  the  default
						if  LC_CTYPE is unset or POSIX
						respectively C.	 8
			  gmacs			Enable	 gmacs-like   (Gosling
						emacs)	command	 line  editing
						(interactive   shells	only);
						currently  identical  to emacs
						editing except that  transpose
						(^T)   acts  slightly  differ‐
						ently.

			  ignoreeof		The shell  will	 not  (easily)
						exit  on  when	end-of-file is
						read, exit must be  used.   To
						avoid	infinite   loops,  the
						shell will exit if eof is read
						13 times in a row.
			  nohup			Do  not kill running jobs with
						a  HUP	signal	when  a	 login
						shell  exists.	 Currently set
						by  default,  but  this	  will
						change	in  the	 future	 to be
						compatible with	 the  original
						Korn shell (which doesn't have
						this option, but does send the
						HUP signal).
			  nolog			No  effect  -  in the original
						Korn  shell,   this   prevents
						function    definitions	  from
						being stored  in  the  history
						file.
			  physical		Causes the cd and pwd commands
						to use `physical'  (i.e.,  the
						filesystem's)  ..  directories
						instead of `logical'  directo‐
						ries (i.e.,  the shell handles
						.., which allows the  user  to
						be  oblivious of symlink links
						to  directories).   Clear   by
						default.   Note	 that  setting
						this option  does  not	effect
						the  current  value of the PWD
						parameter; only the cd command
						changes	 PWD.	See the cd and
						pwd commands  above  for  more
						details.
			  posix			Enable	posix mode.  See POSIX
						Mode above.
			  vi			Enable	vi-like	 command  line
						editing	  (interactive	shells
						only).
			  viraw			No effect -  in	 the  original
						Korn  shell,  unless viraw was
						set, the vi command line  mode
						would  let  the	 tty driver do
						the work until	ESC  (^[)  was
						entered.   pdksh  is always in
						viraw mode.
			  vi-esccomplete	In vi command line editing, do
						command / file name completion
						when escape (^[) is entered in
						command mode.
			  vi-show8		Prefix	 characters  with  the
						eighth bit set with `M-'.   If
						this  option is not set, char‐
						acters in  the	range  128-160
						are  printed  as is, which may
						cause problems.
			  vi-tabcomplete	In vi command line editing, do
						command / file name completion
						when tab (^I)  is  entered  in
						insert	 mode.	 This  is  the
						default.

	      These options can also be used upon  invocation  of  the	shell.
	      The  current  set	 of  options (with single letter names) can be
	      found in the parameter -.	 set -o with no option name will  list
	      all the options and whether each is on or off; set +o will print
	      the long names of all options that are currently on.

	      Remaining arguments, if any, are positional parameters  and  are
	      assigned,	 in  order,  to the positional parameters (i.e., 1, 2,
	      etc.).  If options are ended with -- and there are no  remaining
	      arguments, all positional parameters are cleared.	 If no options
	      or arguments are	given,	then  the  values  of  all  names  are
	      printed.	 For  unknown  historical  reasons, a lone - option is
	      treated specially: it clears both the -x and -v options.

       shift [number]
	      The positional parameters number+1, number+2 etc. are renamed to
	      1, 2, etc.  number defaults to 1.

       test expression

       [ expression ]
	      test evaluates the expression and returns zero status if true, 1
	      if false, and greater than 1 if there was an error.  It is  nor‐
	      mally  used as the condition command of if and while statements.
	      The following basic expressions are available:

	       str		    str has non-zero  length.	Note
				    that  there is the potential for
				    problems if str turns out to  be
				    an	operator  (e.g., -r) - it is
				    generally better to use  a	test
				    like
					    [ X"str" != X ]
				    instead  (double quotes are used
				    in case str contains  spaces  or
				    file globing characters).
	       -r file		    file exists and is readable.
	       -w file		    file exists and is writable.
	       -x file		    file exists and is executable.
	       -a file		    file exists.
	       -e file		    file exists.
	       -f file		    file is a regular file.
	       -d file		    file is a directory.
	       -c file		    file   is  a  character  special
				    device.
	       -b file		    file is a block special device.
	       -p file		    file is a named pipe.
	       -u file		    file's mode has setuid bit set.
	       -g file		    file's mode has setgid bit set.
	       -k file		    file's mode has sticky bit set.
	       -s file		    file is not empty.
	       -O file		    file's  owner  is  the   shell's
				    effective user-ID.
	       -G file		    file's   group  is	the  shell's
				    effective group-ID.
	       -h file		    file is a symbolic link.
	       -H file		    file  is  a	 context   dependent
				    directory  (only  useful  on HP-
				    UX).
	       -L file		    file is a symbolic link.
	       -S file		    file is a socket.
	       -o option	    shell option  is  set  (see	 set
				    command   above   for   list  of
				    options).	As  a	non-standard
				    extension,	if the option starts
				    with a !, the test	is  negated;
				    the	 test always fails if option
				    doesn't exist (thus
					 [ -o foo -o -o !foo ]
				    returns  true  if  and  only  if
				    option foo exists).
	       file -nt file	    first  file is newer than second
				    file or first  file	 exists	 and
				    the second file does not.
	       file -ot file	    first  file is older than second
				    file or second file	 exists	 and
				    the first file does not.
	       file -ef file	    first  file	 is the same file as
				    second file.
	       -t [fd]		    file descriptor is a tty device.
				    If	the  posix  option  (set  -o
				    posix, see POSIX Mode above)  is
				    not	 set, fd may be left out, in
				    which case it is taken to  be  1
				    (the  behaviour  differs  due to
				    the	   special    POSIX    rules
				    described below).

	       string		    string is not empty.
	       -z string	    string is empty.
	       -n string	    string is not empty.
	       string = string	    strings are equal.
	       string == string	    strings are equal.
	       string != string	    strings are not equal.
	       number -eq number    numbers compare equal.
	       number -ne number    numbers compare not equal.
	       number -ge number    numbers  compare greater than or
				    equal.
	       number -gt number    numbers compare greater than.
	       number -le number    numbers  compare  less  than  or
				    equal.
	       number -lt number    numbers compare less than.

	      The  above  basic	 expressions,  in  which  unary operators have
	      precedence over binary operators, may be combined with the  fol‐
	      lowing operators (listed in increasing order of precedence):

	       expr -o expr    logical or
	       expr -a expr    logical and
	       ! expr	       logical not
	       ( expr )	       grouping

	      On  operating  systems not supporting /dev/fd/n devices (where n
	      is a file descriptor number), the test command will  attempt  to
	      fake  it	for  all  tests	 that  operate on files (except the -e
	      test).  I.e., [ -w /dev/fd/2 ] tests if  file  descriptor	 2  is
	      writable.

	      Note  that some special rules are applied (courtesy of POSIX) if
	      the number of arguments to test or [ ... ] is less than five: if
	      leading  ! arguments can be stripped such that only one argument
	      remains then a string length test is performed (again,  even  if
	      the argument is a unary operator); if leading ! arguments can be
	      stripped such that three arguments remain and the	 second	 argu‐
	      ment  is	a  binary  operator, then the binary operation is per‐
	      formed (even if first argument is a unary operator, including an
	      unstripped !).

	      Note:  A	common mistake is to use if [ $foo = bar ] which fails
	      if parameter foo is null or unset, if  it	 has  embedded	spaces
	      (i.e.,  IFS  characters), or if it is a unary operator like ! or
	      -n.  Use tests like if [ "X$foo" = Xbar ] instead.

       time [-p] [ pipeline ]
	      If a pipeline is given, the times used to execute	 the  pipeline
	      are reported.  If no pipeline is given, then the user and system
	      time used by the shell itself, and all the commands it  has  run
	      since  it was started, are reported.  The times reported are the
	      real time (elapsed time from start to finish), the user CPU time
	      (time  spent running in user mode) and the system CPU time (time
	      spent running in kernel mode).  Times are reported  to  standard
	      error; the format of the output is:
		  0.00s real	 0.00s user	0.00s system
	      unless  the  -p  option is given (only possible if pipeline is a
	      simple command), in which case the output is slightly longer:
		  real	 0.00
		  user	 0.00
		  sys	 0.00
	      (the number of digits after the decimal may vary from system  to
	      system).	Note that simple redirections of standard error do not
	      effect the output of the time command:
				   time sleep 1 2> afile
				 { time sleep 1; } 2> afile
	      times for the first command do not go to afile, but those of the
	      second command do.

       times  Print  the  accumulated  user and system times used by the shell
	      and by processes which have exited that the shell started.

       trap [handler signal ...]
	      Sets trap handler that is to be executed when any of the	speci‐
	      fied  signals  are  received.   Handler is either a null string,
	      indicating the signals are to be ignored, a minus (-),  indicat‐
	      ing  that the default action is to be taken for the signals (see
	      signal(3)), or a string containing shell commands to  be	evalu‐
	      ated  and executed at the first opportunity (i.e., when the cur‐
	      rent command completes, or before printing the next PS1  prompt)
	      after  receipt  of  one of the signals.  Signal is the name of a
	      signal (e.g., PIPE or ALRM) or the number	 of  the  signal  (see
	      kill  -l	command	 above).   There are two special signals: EXIT
	      (also known as 0), which is executed when the shell is about  to
	      exit,  and ERR which is executed after an error occurs (an error
	      is something that would cause the shell to exit  if  the	-e  or
	      errexit option were set — see set command above).	 EXIT handlers
	      are executed in the environment of the  last  executed  command.
	      Note that for non-interactive shells, the trap handler cannot be
	      changed for signals that were ignored when the shell started.

	      With no arguments, trap lists, as a series of trap commands, the
	      current  state  of  the traps that have been set since the shell
	      started.	Note that the output of trap can not be usefully piped
	      to  another  process  (an	 artifact  of  the fact that traps are
	      cleared when subprocesses are created).

	      The original Korn shell's DEBUG trap and the handling of ERR and
	      EXIT traps in functions are not yet implemented.

       true   A command that exits with a zero value.

       typeset	[[±Ulprtux]  [-L[n]]  [-R[n]]  [-Z[n]]	[-i[n]]	 |  -f [-tux]]
       [name[=value] ...]
	      Display or set parameter attributes.  With  no  name  arguments,
	      parameter	 attributes are displayed: if no options arg used, the
	      current attributes of all parameters are printed as typeset com‐
	      mands;  if  an  option is given (or - with no option letter) all
	      parameters and their values with the  specified  attributes  are
	      printed;	if options are introduced with +, parameter values are
	      not printed.

	      If name arguments are given, the attributes of the named parame‐
	      ters  are	 set  (-)  or  cleared (+).  Values for parameters may
	      optionally be specified.	If typeset is used inside a  function,
	      any newly created parameters are local to the function.

	      When  -f	is  used,  typeset operates on the attributes of func‐
	      tions.  As with parameters, if no names are given, functions are
	      listed  with their values (i.e., definitions) unless options are
	      introduced with +, in which case only  the  function  names  are
	      reported.

	       -Ln		 Left justify attribute: n specifies the field
				 width.	 If n is not  specified,  the  current
				 width	of  a  parameter  (or the width of its
				 first assigned value) is used.	 Leading white
				 space (and zeros, if used with the -Z option)
				 is stripped.  If necessary, values are either
				 truncated  or	space  padded to fit the field
				 width.
	       -Rn		 Right	justify	 attribute:  n	specifies  the
				 field width.  If n is not specified, the cur‐
				 rent width of a parameter (or	the  width  of
				 its  first assigned value) is used.  Trailing
				 white space are stripped.  If necessary, val‐
				 ues are either stripped of leading characters
				 or space padded to make them  fit  the	 field
				 width.
	       -Zn		 Zero fill attribute: if not combined with -L,
				 this is the same as -R, except	 zero  padding
				 is used instead of space padding.
	       -in		 integer  attribute:  n	 specifies the base to
				 use when displaying the integer (if not spec‐
				 ified, the base given in the first assignment
				 is used).  Parameters with this attribute may
				 be   assigned	values	containing  arithmetic
				 expressions.

	       -U		 unsigned  integer  attribute:	integers   are
				 printed  as unsigned values (only useful when
				 combined with the -i option).	This option is
				 not in the original Korn shell.
	       -f		 Function  mode:  display or set functions and
				 their attributes, instead of parameters.
	       -l		 Lower case attribute: all  upper case charac‐
				 ters  in  values are converted to lower case.
				 (In the original Korn shell,  this  parameter
				 meant	`long  integer'	 when used with the -i
				 option).
	       -p		 Print complete typeset commands that  can  be
				 used to re-create the attributes (but not the
				 values) of parameters.	 This is  the  default
				 action	 (option  exists for ksh93 compatibil‐
				 ity).
	       -r		 Readonly attribute: parameters with the  this
				 attribute  may	 not  be assigned to or unset.
				 Once this attribute is set,  it  can  not  be
				 turned off.
	       -t		 Tag  attribute:  has no meaning to the shell;
				 provided for application use.

				 For functions, -t  is	the  trace  attribute.
				 When  functions  with the trace attribute are
				 executed, the xtrace  (-x)  shell  option  is
				 temporarily turned on.
	       -u		 Upper	case attribute: all lower case charac‐
				 ters in values are converted to  upper	 case.
				 (In  the  original Korn shell, this parameter
				 meant `unsigned integer' when used  with  the
				 -i  option,  which  meant  upper case letters
				 would never be used for  bases	 greater  than
				 10.  See the -U option).

				 For functions, -u is the undefined attribute.
				 See Functions above for the  implications  of
				 this.
	       -x		 Export	 attribute:  parameters (or functions)
				 are placed in the environment of any executed
				 commands.   Exported functions are not imple‐
				 mented yet.

       ulimit [-abcdfHlmnpsStvw] [value]
	      Display or set process limits.  If no options are used, the file
	      size  limit (-f) is assumed.  value, if specified, may be either
	      be an arithmetic expression or the word unlimited.   The	limits
	      affect  the shell and any processes created by the shell after a
	      limit is imposed.	 Note that some systems may not	 allow	limits
	      to  be increased once they are set.  Also note that the types of
	      limits available are system dependent - some systems  have  only
	      the -f limit.

	      -a     Displays  all  limits; unless -H is used, soft limits are
		     displayed.

	      -H     Set the hard limit only (default is to set both hard  and
		     soft limits).

	      -S     Set  the soft limit only (default is to set both hard and
		     soft limits).

	      -b     Impose a size limit of n bytes on the size of socket buf‐
		     fers.

	      -c     Impose  a	size  limit  of	 n  blocks on the size of core
		     dumps.

	      -d     Impose a size limit of n kbytes on the size of  the  data
		     area.

	      -f     Impose  a	size limit of n blocks on files written by the
		     shell and its child processes (files of any size  may  be
		     read).

	      -l     Impose  a	limit  of  n  kbytes  on  the amount of locked
		     (wired) physical memory.

	      -m     Impose a limit of n kbytes on the amount of physical mem‐
		     ory used.

	      -n     Impose  a limit of n file descriptors that can be open at
		     once.

	      -p     Impose a limit of n processes that can be run by the user
		     at any one time.

	      -s     Impose  a size limit of n kbytes on the size of the stack
		     area.

	      -t     Impose a time limit of n CPU seconds to be used  by  each
		     process.

	      -v     Impose  a limit of n kbytes on the amount of virtual mem‐
		     ory used; on some systems this is the  maximum  allowable
		     virtual address (in bytes, not kbytes).

	      -w     Impose  a	limit  of n kbytes on the amount of swap space
		     used.

	      As far as ulimit is concerned, a block is 512 bytes.

       umask [-S] [mask]
	      Display or set the file permission creation mask, or umask  (see
	      umask(2)).   If the -S option is used, the mask displayed or set
	      is symbolic, otherwise it is an octal number.

	      Symbolic masks are like those used by chmod(1):
		     [ugoa]{{=+-}{rwx}*}+[,...]
	      in which the first group of characters is the who part, the sec‐
	      ond  group  is the op part, and the last group is the perm part.
	      The who part specifies which part of the umask is	 to  be	 modi‐
	      fied.  The letters mean:

		     u	    the user permissions

		     g	    the group permissions

		     o	    the other permissions (non-user, non-group)

		     a	    all permissions (user, group and other)

	      The  op  part  indicates how the who permissions are to be modi‐
	      fied:

		     =	    set

		     +	    added to

		     -	    removed from

	      The perm part specifies which permissions are to be  set,	 added
	      or removed:

		     r	    read permission

		     w	    write permission

		     x	    execute permission

	      When symbolic masks are used, they describe what permissions may
	      be made available (as opposed to octal masks in which a set  bit
	      means  the  corresponding	 bit  is  to  be  cleared).   Example:
	      `ug=rwx,o=' sets	the  mask  so  files  will  not	 be  readable,
	      writable	or  executable by `others', and is equivalent (on most
	      systems) to the octal mask `07'.

       unalias [-adt] [name1 ...]
	      The aliases for the given names are removed.  If the  -a	option
	      is  used,	 all aliases are removed.  If the -t or -d options are
	      used, the indicated operations are carried  out  on  tracked  or
	      directory aliases, respectively.

       unset [-fv] parameter ...
	      Unset  the named parameters (-v, the default) or functions (-f).
	      The exit status is  non-zero  if	any  of	 the  parameters  were
	      already unset, zero otherwise.

       wait [job]
	      Wait  for	 the  specified	 job(s) to finish.  The exit status of
	      wait is that of the last specified  job:	if  the	 last  job  is
	      killed  by  a signal, the exit status is 128 + the number of the
	      signal (see kill -l exit-status above); if  the  last  specified
	      job  can't  be  found  (because it never existed, or had already
	      finished), the exit status of wait  is  127.   See  Job  Control
	      below  for  the format of job.  Wait will return if a signal for
	      which a trap has been set is received, or if a HUP, INT or  QUIT
	      signal is received.

	      If  no  jobs are specified, wait waits for all currently running
	      jobs (if any) to finish and exits with a zero  status.   If  job
	      monitoring  is enabled, the completion status of jobs is printed
	      (this is not the case when jobs are explicitly specified).

       whence [-pv] [name ...]
	      For each name, the type of command  is  listed  (reserved	 word,
	      built-in, alias, function, tracked alias or executable).	If the
	      -p option is used, a path search done even if name is a reserved
	      word,  alias,  etc.  Without the -v option, whence is similar to
	      command -v except that whence will find reserved words and won't
	      print  aliases  as alias commands; with the -v option, whence is
	      the same as command -V.  Note that for  whence,  the  -p	option
	      does  not	 affect	 the search path used, as it does for command.
	      If the type of one or more of the names could not be determined,
	      the exit status is non-zero.

   Job Control
       Job  control refers to the shell's ability to monitor and control jobs,
       which are processes or groups of	 processes  created  for  commands  or
       pipelines.   At	a  minimum, the shell keeps track of the status of the
       background (i.e., asynchronous) jobs that currently exist; this	infor‐
       mation  can  be	displayed  using  the jobs command.  If job control is
       fully enabled (using set -m or set -o monitor), as it is	 for  interac‐
       tive  shells,  the  processes  of a job are placed in their own process
       group, foreground jobs can be stopped by typing the  suspend  character
       from  the  terminal  (normally ^Z), jobs can be restarted in either the
       foreground or background, using the fg and bg  commands,	 respectively,
       and  the	 state	of the terminal is saved or restored when a foreground
       job is stopped or restarted, respectively.

       Note that only commands that create processes (e.g., asynchronous  com‐
       mands,  subshell commands, and non-built-in, non-function commands) can
       be stopped; commands like read cannot be.

       When a job is created, it is assigned a	job-number.   For  interactive
       shells, this number is printed inside [..], followed by the process-ids
       of the processes in the job when an asynchronous command is run.	 A job
       may  be	referred  to in bg, fg, jobs, kill and wait commands either by
       the process id of the last process in the command pipeline  (as	stored
       in the $! parameter) or by prefixing the job-number with a percent sign
       (%).  Other percent sequences can also be used to refer to jobs:

	%+			 The most recently stopped job, or,  if	 there
				 are no stopped jobs, the oldest running job.
	%%, %			 Same as %+.
	%-			 The  job  that	 would	be  the %+ job, if the
				 later did not exist.
	%n			 The job with job-number n.
	%?string		 The job  containing  the  string  string  (an
				 error occurs if multiple jobs are matched).
	%string			 The job starting with string string (an error
				 occurs if multiple jobs are matched).

       When a job changes state (e.g., a background job finishes or foreground
       job is stopped), the shell prints the following status information:
	      [number] flag status command
       where

	number
	      is the job-number of the job.

	flag  is + or - if the job is the %+ or %- job, respectively, or space
	      if it is neither.

	status
	      indicates the current state of the job and can be

	      Running
		     the job has neither stopped or exited (note that  running
		     does  not	necessarily  mean  consuming  CPU  time	 — the
		     process could be blocked waiting for some event).

	      Done [(number)]
		     the job exited.  number is the exit status	 of  the  job,
		     which is omitted if the status is zero.

	      Stopped [(signal)]
		     the job was stopped by the indicated signal (if no signal
		     is given, the job was stopped by SIGTSTP).

	      signal-description [(core dumped)]
		     the job was  killed  by  a	 signal	 (e.g.,	 Memory fault,
		     Hangup,  etc. — use kill -l for a list of signal descrip‐
		     tions).  The (core dumped) message indicates the  process
		     created a core file.

	command
	      is  the command that created the process.	 If there are multiple
	      processes in the job, then each process will have a line showing
	      its command and possibly its status, if it is different from the
	      status of the previous process.

       When an attempt is made to exit the shell while there are jobs  in  the
       stopped state, the shell warns the user that there are stopped jobs and
       does not exit.  If another attempt is  immediately  made	 to  exit  the
       shell,  the  stopped  jobs  are	sent a HUP signal and the shell exits.
       Similarly, if the nohup option is not set and there  are	 running  jobs
       when an attempt is made to exit a login shell, the shell warns the user
       and does not exit.  If another attempt is immediately made to exit  the
       shell, the running jobs are sent a HUP signal and the shell exits.

   Interactive Input Line Editing
       The  shell  supports three modes of reading command lines from a tty in
       an interactive session.	Which is used  is  controlled  by  the	emacs,
       gmacs and vi set options (at most one of these can be set at once).  If
       none of these options is enabled, the shell simply  reads  lines	 using
       the  normal tty driver.	If the emacs or gmacs option is set, the shell
       allows emacs like editing of the command; similarly, if the  vi	option
       is  set,	 the shell allows vi like editing of the command.  These modes
       are described in detail in the following sections.

       In these editing modes, if a line is longer that the screen width  (see
       COLUMNS parameter), a >, + or < character is displayed in the last col‐
       umn indicating that there are more characters after, before and	after,
       or  before  the	current	 position, respectively.  The line is scrolled
       horizontally as necessary.

   Emacs Editing Mode
       When the emacs  option  is  set,	 interactive  input  line  editing  is
       enabled.	  Warning: This mode is slightly different from the emacs mode
       in the original Korn shell and the 8th bit is stripped in  emacs	 mode.
       In  this	 mode various editing commands (typically bound to one or more
       control characters) cause immediate actions without waiting for a  new-
       line.  Several editing commands are bound to particular control charac‐
       ters when the shell is invoked; these bindings can be changed using the
       following commands:

       bind   The current bindings are listed.

       bind string=[editing-command]
	      The  specified  editing  command	is  bound to the given string,
	      which should consist of a control character (which may be	 writ‐
	      ten  using caret notation ^X), optionally preceded by one of the
	      two prefix characters.  Future input of the  string  will	 cause
	      the  editing  command  to	 be  immediately  invoked.   Note that
	      although only two prefix characters (usually  ESC	 and  ^X)  are
	      supported, some multi-character sequences can be supported.  The
	      following binds the arrow keys on an  ANSI  terminal,  or	 xterm
	      (these  are  in  the  default  bindings).	 Of course some escape
	      sequences won't work out quite this nicely:

	      bind '^[['=prefix-2
	      bind '^XA'=up-history
	      bind '^XB'=down-history
	      bind '^XC'=forward-char
	      bind '^XD'=backward-char

       bind -l
	      Lists the names of the functions to which keys may be bound.

       bind -m string=[substitute]
	      The  specified  input  string  will  afterwards  be  immediately
	      replaced by the given substitute string, which may contain edit‐
	      ing commands.

       The following is a list of editing commands available.	Each  descrip‐
       tion  starts  with  the name of the command, a n, if the command can be
       prefixed with a count, and any keys the command is bound to by  default
       (written	 using caret notation, e.g., ASCII ESC character is written as
       ^[).  A count prefix for a command is entered using the	sequence  ^[n,
       where  n is a sequence of 1 or more digits; unless otherwise specified,
       if a count is omitted, it defaults to 1.	  Note	that  editing  command
       names  are  used only with the bind command.  Furthermore, many editing
       commands are useful only on  terminals  with  a	visible	 cursor.   The
       default	bindings were chosen to resemble corresponding EMACS key bind‐
       ings.  The users tty characters (e.g., ERASE) are bound	to  reasonable
       substitutes and override the default bindings.

       abort ^G
	      Useful  as  a response to a request for a search-history pattern
	      in order to abort the search.

       auto-insert n
	      Simply causes the character to appear as	literal	 input.	  Most
	      ordinary characters are bound to this.

       backward-char  n ^B
	      Moves the cursor backward n characters.

       backward-word  n ^[B
	      Moves the cursor backward to the beginning of a word; words con‐
	      sist of alphanumerics, underscore (_) and dollar ($).

       beginning-of-history ^[<
	      Moves to the beginning of the history.

       beginning-of-line ^A
	      Moves the cursor to the beginning of the edited input line.

       capitalize-word n ^[c, ^[C
	      Uppercase the first character in the next n words,  leaving  the
	      cursor  past the end of the last word.  If the current line does
	      not begin with a comment character, one is added at  the	begin‐
	      ning  of the line and the line is entered (as if return had been
	      pressed), otherwise the existing comment characters are  removed
	      and the cursor is placed at the beginning of the line.

       complete ^[^[

       complete ^I
	      Automatically completes as much as is unique of the command name
	      or the file name containing the cursor.  If the entire remaining
	      command or file name is unique a space is printed after its com‐
	      pletion, unless it is a  directory  name	in  which  case	 /  is
	      appended.	  If there is no command or file name with the current
	      partial word as its prefix, a bell character is output  (usually
	      causing a audio beep).

       complete-command ^X^[
	      Automatically completes as much as is unique of the command name
	      having the partial word up to the cursor as its  prefix,	as  in
	      the complete command described above.

       complete-file ^[^X
	      Automatically  completes	as  much as is unique of the file name
	      having the partial word up to the cursor as its  prefix,	as  in
	      the complete command described above.

       complete-list ^[=
	      List the possible completions for the current word.

       delete-char-backward n ERASE, ^?, ^H
	      Deletes n characters before the cursor.

       delete-char-forward n
	      Deletes n characters after the cursor.

       delete-word-backward n ^[ERASE, ^[^?, ^[^H, ^[h
	      Deletes n words before the cursor.

       delete-word-forward n ^[d
	      Deletes characters after the cursor up to the end of n words.

       down-history n ^N
	      Scrolls  the history buffer forward n lines (later).  Each input
	      line originally starts just after the last entry in the  history
	      buffer,  so  down-history is not useful until either search-his‐
	      tory or up-history has been performed.

       downcase-word n ^[L, ^[l
	      Lowercases the next n words.

       end-of-history ^[>
	      Moves to the end of the history.

       end-of-line ^E
	      Moves the cursor to the end of the input line.

       eot ^_ Acts as an end-of-file; this is useful because  edit-mode	 input
	      disables normal terminal input canonicalization.

       eot-or-delete n ^D
	      Acts  as	eot if alone on a line; otherwise acts as delete-char-
	      forward.

       error  Error (ring the bell).

       exchange-point-and-mark ^X^X
	      Places the cursor where the mark is, and sets the mark to	 where
	      the cursor was.

       expand-file ^[*
	      Appends  a  * to the current word and replaces the word with the
	      result of performing file globbing on the	 word.	 If  no	 files
	      match the pattern, the bell is rung.

       forward-char n ^F
	      Moves the cursor forward n characters.

       forward-word n ^[f
	      Moves the cursor forward to the end of the nth word.

       goto-history n ^[g
	      Goes to history number n.

       kill-line KILL
	      Deletes the entire input line.

       kill-region ^W
	      Deletes the input between the cursor and the mark.

       kill-to-eol n ^K
	      Deletes the input from the cursor to the end of the line if n is
	      not specified, otherwise deletes characters between  the	cursor
	      and column n.

       list ^[?
	      Prints  a sorted, columnated list of command names or file names
	      (if any) that can complete the partial word containing the  cur‐
	      sor.  Directory names have / appended to them.

       list-command ^X?
	      Prints  a sorted, columnated list of command names (if any) that
	      can complete the partial word containing the cursor.

       list-file ^X^Y
	      Prints a sorted, columnated list of file names (if any) that can
	      complete	the  partial  word  containing	the cursor.  File type
	      indicators are appended as described under list above.

       newline ^J, ^M
	      Causes the current input line to be processed by the shell.  The
	      current cursor position may be anywhere on the line.

       newline-and-next ^O
	      Causes  the current input line to be processed by the shell, and
	      the next line from history becomes the current  line.   This  is
	      only useful after an up-history or search-history.

       no-op QUIT
	      This does nothing.

       prefix-1 ^[
	      Introduces a 2-character command sequence.

       prefix-2 ^X

       prefix-2 ^[[
	      Introduces a 2-character command sequence.

       prev-hist-word n ^[., ^[_
	      The  last	 (nth) word of the previous command is inserted at the
	      cursor.

       quote ^^
	      The following character is taken literally  rather  than	as  an
	      editing command.

       redraw ^L
	      Reprints the prompt string and the current input line.

       search-character-backward n ^[^]
	      Search  backward	in  the current line for the nth occurrence of
	      the next character typed.

       search-character-forward n ^]
	      Search forward in the current line for the nth occurrence of the
	      next character typed.

       search-history ^R
	      Enter  incremental  search  mode.	  The internal history list is
	      searched backwards for commands matching the input.  An  initial
	      ^	 in  the search string anchors the search.  The abort key will
	      leave search mode.  Other commands will be executed after	 leav‐
	      ing  search  mode.   Successive search-history commands continue
	      searching backward to the next previous occurrence of  the  pat‐
	      tern.  The history buffer retains only a finite number of lines;
	      the oldest are discarded as necessary.

       set-mark-command ^[<space>
	      Set the mark at the cursor position.

       stuff  On systems supporting it, pushes the bound character  back  onto
	      the  terminal  input  where it may receive special processing by
	      the terminal handler.  This is useful for the BRL ^T mini-systat
	      feature, for example.

       stuff-reset
	      Acts like stuff, then aborts input the same as an interrupt.

       transpose-chars ^T
	      If  at  the  end	of  line,  or if the gmacs option is set, this
	      exchanges the two previous characters; otherwise,	 it  exchanges
	      the  previous  and  current  characters and moves the cursor one
	      character to the right.

       up-history n ^P
	      Scrolls the history buffer backward n lines (earlier).

       upcase-word n ^[U, ^[u
	      Uppercases the next n words.

       version ^V
	      Display the version of ksh.  The current edit buffer is restored
	      as soon as any key is pressed (the key is then processed, unless
	      it is a space).

       yank ^Y
	      Inserts the most recently killed text string at the current cur‐
	      sor position.

       yank-pop ^[y
	      Immediately after a yank, replaces the inserted text string with
	      the next previous killed text string.

   Vi Editing Mode
       The vi command line editor in ksh has basically the  same  commands  as
       the vi editor (see vi(1)), with the following exceptions:

	 ·    you start out in insert mode,

	 ·    there  are  file	name and command completion commands (=, \, *,
	      ^X, ^E, ^F and, optionally, <tab>),

	 ·    the _ command is different (in ksh it is the last argument  com‐
	      mand, in vi it goes to the start of the current line),

	 ·    the  /  and  G  commands move in the opposite direction as the j
	      command

	 ·    and commands which don't make sense in a single line editor  are
	      not  available  (e.g.,  screen movement commands, ex : commands,
	      etc.).

       Note that the ^X stands for control-X; also <esc>,  <space>  and	 <tab>
       are used for escape, space and tab, respectively (no kidding).

       Like  vi, there are two modes: insert mode and command mode.  In insert
       mode, most characters are simply put in the buffer at the current  cur‐
       sor  position  as  they are typed, however, some characters are treated
       specially.  In particular, the following characters are taken from cur‐
       rent  tty  settings  (see stty(1)) and have their usual meaning (normal
       values are in parentheses): kill (^U), erase  (^?),  werase  (^W),  eof
       (^D), intr (^C) and quit (^\).  In addition to the above, the following
       characters are also treated specially in insert mode:

	^H			 erases previous character
	^V			 literal next: the next character typed is not
				 treated  specially (can be used to insert the
				 characters being described here)
	^J ^M			 end of line: the current line is read, parsed
				 and executed by the shell
	<esc>			 puts the editor in command mode (see below)
	^E			 command and file name enumeration (see below)
	^F			 command and file name completion (see below).
				 If used twice in a row, the list of  possible
				 completions  is  displayed;  if  used a third
				 time, the completion is undone.
	^X			 command and file name expansion (see below)
	<tab>			 optional file	name  and  command  completion
				 (see  ^F  above), enabled with set -o vi-tab‐
				 complete

       In command mode, each character is interpreted as a  command.   Charac‐
       ters  that  don't  correspond  to commands, are illegal combinations of
       commands or are commands that can't be carried out all cause beeps.  In
       the  following  command	descriptions, a n indicates the command may be
       prefixed by a number (e.g., 10l moves right 10 characters); if no  num‐
       ber  prefix  is	used, n is assumed to be 1 unless otherwise specified.
       The term `current position' refers to the position between  the	cursor
       and the character preceding the cursor.	A `word' is a sequence of let‐
       ters, digits and underscore characters or  a  sequence  of  non-letter,
       non-digit,  non-underscore,  non-white-space  characters	 (e.g., ab2*&^
       contains two words) and a `big-word' is a sequence  of  non-white-space
       characters.

       Special ksh vi commands
	      The  following  commands	are not in, or are different from, the
	      normal vi file editor:

	      n_     insert a space followed by the nth big-word from the last
		     command  in the history at the current position and enter
		     insert mode; if n is not  specified,  the	last  word  is
		     inserted.

	      #	     insert the comment character (#) at the start of the cur‐
		     rent line and return the line to the shell (equivalent to
		     I#^J).

	      ng     like G, except if n is not specified, it goes to the most
		     recent remembered line.

	      nv     edit line n using the vi editor; if n is  not  specified,
		     the  current line is edited.  The actual command executed
		     is `fc -e ${VISUAL:-${EDITOR:-vi}} n'.

	      * and ^X
		     command or file name expansion is applied to the  current
		     big-word  (with  an  appended  *, if the word contains no
		     file globing characters) - the big-word is replaced  with
		     the  resulting  words.   If  the  current big-word is the
		     first on the line (or follows one of the following	 char‐
		     acters:  ;,  |, &, (, )) and does not contain a slash (/)
		     then command  expansion  is  done,	 otherwise  file  name
		     expansion is done.	 Command expansion will match the big-
		     word against all aliases, functions and built-in commands
		     as	 well  as  any executable files found by searching the
		     directories in the PATH parameter.	 File  name  expansion
		     matches  the  big-word  against  the files in the current
		     directory.	 After expansion, the cursor  is  placed  just
		     past the last word and the editor is in insert mode.

	      n\, n^F, n<tab> and n<esc>
		     command/file  name	 completion:  replace the current big-
		     word with the longest unique match	 obtained  after  per‐
		     forming  command/file name expansion.  <tab> is only rec‐
		     ognized if the vi-tabcomplete option is set, while	 <esc>
		     is	 only  recognized  if the vi-esccomplete option is set
		     (see set -o).  If n is specified, the nth	possible  com‐
		     pletion is selected (as reported by the command/file name
		     enumeration command).

	      = and ^E
		     command/file name enumeration: list all the  commands  or
		     files that match the current big-word.

	      ^V     display  the  version  of	pdksh;	it  is displayed until
		     another key is pressed (this key is ignored).

	      @c     macro expansion: execute the commands found in the	 alias
		     _c.

       Intra-line movement commands

	      nh and n^H
		     move left n characters.

	      nl and n<space>
		     move right n characters.

	      0	     move to column 0.

	      ^	     move to the first non white-space character.

	      n|     move to column n.

	      $	     move to the last character.

	      nb     move back n words.

	      nB     move back n big-words.

	      ne     move forward to the end the word, n times.

	      nE     move forward to the end the big-word, n times.

	      nw     move forward n words.

	      nW     move forward n big-words.

	      %	     find  match:  the	editor	looks  forward for the nearest
		     parenthesis, bracket or brace and then moves the  to  the
		     matching parenthesis, bracket or brace.

	      nfc    move forward to the nth occurrence of the character c.

	      nFc    move backward to the nth occurrence of the character c.

	      ntc    move  forward  to	just  before the nth occurrence of the
		     character c.

	      nTc    move backward to just before the nth  occurrence  of  the
		     character c.

	      n;     repeats the last f, F, t or T command.

	      n,     repeats  the  last f, F, t or T command, but moves in the
		     opposite direction.

       Inter-line movement commands

	      nj and n+ and n^N
		     move to the nth next line in the history.

	      nk and n- and n^P
		     move to the nth previous line in the history.

	      nG     move to line n in the history; if n is not specified, the
		     number first remembered line is used.

	      ng     like G, except if n is not specified, it goes to the most
		     recent remembered line.

	      n/string
		     search backward through the history for the nth line con‐
		     taining string; if string starts with ^, the remainder of
		     the string must appear at the start of the	 history  line
		     for it to match.

	      n?string
		     same  as  /,  except it searches forward through the his‐
		     tory.

	      nn     search for the nth occurrence of the last search  string;
		     the  direction  of	 the  search  is  the same as the last
		     search.

	      nN     search for the nth occurrence of the last search  string;
		     the  direction  of the search is the opposite of the last
		     search.

       Edit commands

	      na     append text n times: goes into insert mode just after the
		     current  position.	 The append is only replicated if com‐
		     mand mode is re-entered (i.e., <esc> is used).

	      nA     same as a, except it appends at the end of the line.

	      ni     insert text n times: goes into insert mode at the current
		     position.	 The  insertion	 is only replicated if command
		     mode is re-entered (i.e., <esc> is used).

	      nI     same as i, except the insertion is done just  before  the
		     first non-blank character.

	      ns     substitute	 the next n characters (i.e., delete the char‐
		     acters and go into insert mode).

	      S	     substitute whole line: all characters from the first non-
		     blank character to the end of line are deleted and insert
		     mode is entered.

	      ncmove-cmd
		     change from the current position to the position  result‐
		     ing  from	n move-cmds (i.e., delete the indicated region
		     and go into insert mode); if  move-cmd  is	 c,  the  line
		     starting from the first non-blank character is changed.

	      C	     change  from  the current position to the end of the line
		     (i.e., delete to the end of the line and go  into	insert
		     mode).

	      nx     delete the next n characters.

	      nX     delete the previous n characters.

	      D	     delete to the end of the line.

	      ndmove-cmd
		     delete  from the current position to the position result‐
		     ing from n move-cmds; move-cmd is a movement command (see
		     above) or d, in which case the current line is deleted.

	      nrc    replace the next n characters with the character c.

	      nR     replace: enter insert mode but overwrite existing charac‐
		     ters instead of  inserting	 before	 existing  characters.
		     The replacement is repeated n times.

	      n~     change the case of the next n characters.

	      nymove-cmd
		     yank  from the current position to the position resulting
		     from n move-cmds into the yank buffer; if move-cmd is  y,
		     the whole line is yanked.

	      Y	     yank from the current position to the end of the line.

	      np     paste the contents of the yank buffer just after the cur‐
		     rent position, n times.

	      nP     same as p, except the buffer is  pasted  at  the  current
		     position.

       Miscellaneous vi commands

	      ^J and ^M
		     the  current  line	 is  read,  parsed and executed by the
		     shell.

	      ^L and ^R
		     redraw the current line.

	      n.     redo the last edit command n times.

	      u	     undo the last edit command.

	      U	     undo all changes that have been made to the current line.

	      intr and quit
		     the interrupt and quit terminal characters cause the cur‐
		     rent line to be deleted and a new prompt to be printed.

FILES
       ~/.kshrc
       ~/.profile
       /etc/profile
       /etc/suid_profile

BUGS
       Any  bugs  in  pdksh  should  be	 reported  to pdksh@cs.mun.ca.	Please
       include the version of pdksh (echo $KSH_VERSION shows it), the machine,
       operating system and compiler you are using and a description of how to
       repeat the bug (a small shell  script  that  demonstrates  the  bug  is
       best).  The following, if relevant (if you are not sure, include them),
       can also helpful: options you are using (both options.h options and set
       -o options) and a copy of your config.h (the file generated by the con‐
       figure  script).	  New  versions	 of  pdksh  can	  be   obtained	  from
       ftp://ftp.cs.mun.ca/pub/pdksh/.

       BTW, the most frequently reported bug is
	       echo hi | read a; echo $a   # Does not print hi
       I'm aware of this and there is no need to report it.

VERSION
       This page documents version
			    @(#)PD KSH v5.2.14 99/07/13.2
       of the public domain korn shell.

AUTHORS
       This shell is based on the public domain 7th edition Bourne shell clone
       by Charles Forsyth and parts of the BRL shell by	 Doug  A.  Gwyn,  Doug
       Kingston,  Ron  Natalie,	 Arnold	 Robbins, Lou Salkind and others.  The
       first release of pdksh was created by Eric Gisin,  and  it  was	subse‐
       quently	maintained  by	John R. MacMillan (chance!john@sq.sq.com), and
       Simon J.	 Gerraty  (sjg@zen.void.oz.au).	  The  current	maintainer  is
       Michael	Rendell	 (michael@cs.mun.ca).	The  CONTRIBUTORS  file in the
       source distribution contains a more complete list of people  and	 their
       part in the shell's development.

SEE ALSO
       awk(1),	sh(1),	csh(1), ed(1), getconf(1), getopt(1), sed(1), stty(1),
       vi(1),  dup(2),	execve(2),  getgid(2),	getuid(2),  open(2),  pipe(2),
       wait(2), getopt(3), rand(3), signal(3), system(3), environ(7)

       The KornShell Command and Programming Language, Morris Bolsky and David
       Korn, 1989, ISBN 0-13-516972-0.

       UNIX Shell Programming, Stephen G. Kochan, Patrick H. Wood, Hayden.

       IEEE Standard for information Technology -  Portable  Operating	System
       Interface  (POSIX)  - Part 2: Shell and Utilities, IEEE Inc, 1993, ISBN
       1-55937-255-9.

				August 19, 1996				KSH(1)
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