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sh(1)				 User Commands				 sh(1)

NAME
       sh, jsh - standard and job control shell and command interpreter

SYNOPSIS
       /usr/bin/sh [-acefhiknprstuvx] [argument]...

       /usr/xpg4/bin/sh [± abCefhikmnoprstuvx]
	   [± o option]... [-c string] [arg]...

       /usr/bin/jsh [-acefhiknprstuvx] [argument]...

DESCRIPTION
       The /usr/bin/sh utility is a command programming language that executes
       commands read from a terminal or a file.

       The /usr/xpg4/bin/sh utility is a standards compliant shell. This util‐
       ity provides all the functionality of ksh(1), except in cases discussed
       in ksh(1) where differences in behavior exist.

       The jsh utility is an interface to the shell that provides all  of  the
       functionality  of  sh  and enables job control (see Job Control section
       below).

       Arguments to the shell are listed in the Invocation section below.

   Definitions
       A blank is a tab or a space. A name is a	 sequence  of  ASCII  letters,
       digits,	or  underscores,  beginning  with a letter or an underscore. A
       parameter is a name, a digit, or any of the characters *, @, #,	?,  −,
       $, and !.

USAGE
   Commands
       A  simple-command is a sequence of non-blank words separated by blanks.
       The first word specifies the name of the command to be executed. Except
       as  specified below, the remaining words are passed as arguments to the
       invoked command.	 The  command  name  is	 passed	 as  argument  0  (see
       exec(2)). The value of a simple-command is its exit status if it termi‐
       nates normally, or (octal) 200+status if it terminates abnormally.  See
       signal.h(3HEAD) for a list of status values.

       A  pipeline  is	a sequence of one or more commands separated by |. The
       standard output of each command but the last is connected by a  pipe(2)
       to  the	standard  input	 of the next command. Each command is run as a
       separate process. The shell waits for the last  command	to  terminate.
       The exit status of a pipeline is the exit status of the last command in
       the pipeline.

       A list is a sequence of one or more pipelines separated by ;, &, &&, or
       ||,  and optionally terminated by ; or &.  Of these four symbols, ; and
       & have equal precedence, which is lower than that of  &&	 and  ||.  The
       symbols	&&  and	 || also have equal precedence. A semicolon (;) causes
       sequential execution of the preceding  pipeline,	 that  is,  the	 shell
       waits  for the pipeline to finish before executing any commands follow‐
       ing the semicolon. An ampersand (&) causes  asynchronous	 execution  of
       the preceding pipeline, that is, the shell does not wait for that pipe‐
       line to finish. The symbol && (||) causes the list following it	to  be
       executed	 only if the preceding pipeline returns a zero (non-zero) exit
       status. An arbitrary number of newlines may appear in a	list,  instead
       of semicolons, to delimit commands.

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

       for name [ in word ... ] do list done

	   Each	 time  a for command is executed, name is set to the next word
	   taken from the in word list. If in word ...	is omitted,  then  the
	   for command executes the do list once for each positional parameter
	   that is set (see Parameter Substitution section  below).  Execution
	   ends when there are no more words in the list.

       case word in [ pattern [ | pattern ] ) list ;; ] ...  esac

	   A  case command executes the list associated with the first pattern
	   that matches word. The form of the patterns is  the	same  as  that
	   used	 for  file-name generation (see File Name Generation section),
	   except that a slash, a leading dot, or a dot immediately  following
	   a slash need not be matched explicitly.

       if list ; then list [ elif list ; then list ; ] ... [ else list ; ] fi

       The  list  following if is executed and, if it returns a zero exit sta‐
       tus, the list following the first then is executed. Otherwise, the list
       following  elif is executed and, if its value is zero, the list follow‐
       ing the next then is executed. Failing that, the else list is executed.
       If no else list or then list is executed, then the if command returns a
       zero exit status.

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

       (list)			  Execute list in a sub-shell.

       { list;}			  list	is  executed  in the current (that is,
				  parent) shell. The { must be followed	 by  a
				  space.

       name (){ list;}		  Define  a  function  which  is referenced by
				  name. The body of the function is  the  list
				  of  commands	between { and }. The { must be
				  followed by a space. Execution of  functions
				  is  described below (see Execution section).
				  The { and } are unnecessary if the  body  of
				  the  function is a command as defined above,
				  under Commands.

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

       if  then	 else  elif  fi	 case  esac  for  while	 until	do  done  {  }

   Comments Lines
       A  word beginning with # causes that word and all the following charac‐
       ters up to a newline to be ignored.

   Command Substitution
       The shell reads commands from the string between two grave accents (``)
       and  the standard output from these commands may be used as all or part
       of a word. Trailing newlines from the standard output are removed.

       No interpretation is done on the string	before	the  string  is	 read,
       except to remove backslashes (\) used to escape other characters. Back‐
       slashes may be used to escape a grave accent (`) or  another  backslash
       (\)  and	 are removed before the command string is read. Escaping grave
       accents allows nested command substitution. If the command substitution
       lies  within  a	pair of double quotes (" ...` ...` ... "), a backslash
       used to escape a double quote (\") will be removed; otherwise, it  will
       be left intact.

       If  a  backslash is used to escape a newline character (\newline), both
       the backslash and the newline are removed (see  the  later  section  on
       Quoting). In addition, backslashes used to escape dollar signs (\$) are
       removed. Since no parameter substitution is done on the command	string
       before it is read, inserting a backslash to escape a dollar sign has no
       effect. Backslashes that precede characters other than \,  `,  ",  new‐
       line, and $ are left intact when the command string is read.

   Parameter Substitution
       The  character  $  is used to introduce substitutable parameters. There
       are two types of parameters, positional and keyword. If parameter is  a
       digit,  it  is  a  positional  parameter.  Positional parameters may be
       assigned values by set. Keyword parameters (also	 known	as  variables)
       may be assigned values by writing:

       name=value [ name=value ] ...

       Pattern-matching	 is not performed on value. There cannot be a function
       and a variable with the same name.

       ${parameter}		The value, if any, of the parameter is substi‐
				tuted.	The  braces  are  required  only  when
				parameter is followed by a letter,  digit,  or
				underscore  that  is  not to be interpreted as
				part of its name. If parameter is * or @,  all
				the  positional	 parameters, starting with $1,
				are substituted (separated by spaces). Parame‐
				ter  $0	 is  set  from	argument zero when the
				shell is invoked.

       ${parameter:−word}	Use Default Values. If parameter is  unset  or
				null,  the  expansion  of word is substituted;
				otherwise, the value of parameter  is  substi‐
				tuted.

       ${parameter:=word}	Assign	Default	 Values. If parameter is unset
				or null, the expansion of word is assigned  to
				parameter.  In	all  cases, the final value of
				parameter is substituted. Only variables,  not
				positional  parameters	or special parameters,
				can be assigned in this way.

       ${parameter:?word}	If parameter is set and is  non-null,  substi‐
				tute its value; otherwise, print word and exit
				from the shell. If word is omitted,  the  mes‐
				sage "parameter null or not set" is printed.

       ${parameter:+word}	If  parameter  is set and is non-null, substi‐
				tute word; otherwise substitute nothing.

       In the above, word is not evaluated unless it is to be used as the sub‐
       stituted	 string,  so  that,  in the following example, pwd is executed
       only if d is not set or is null:

	 echo  ${d:−`pwd`}

       If the colon (:) is omitted from the above expressions, the shell  only
       checks whether parameter is set or not.

       The following parameters are automatically set by the shell.

       #       The number of positional parameters in decimal.

       −       Flags  supplied	to  the shell on invocation or by the set com‐
	       mand.

       ?       The decimal value returned by the last  synchronously  executed
	       command.

       $       The process number of this shell.

       !       The process number of the last background command invoked.

       The  following parameters are used by the shell. The parameters in this
       section are also referred to as environment variables.

       HOME	    The default argument (home directory) for the cd  command,
		    set	 to  the  user's  login directory by login(1) from the
		    password file (see passwd(4)).

       PATH	    The	 search	 path  for  commands  (see  Execution  section
		    below).

       CDPATH	    The search path for the cd command.

       MAIL	    If	this  parameter	 is set to the name of a mail file and
		    the MAILPATH  parameter is not set, the shell informs  the
		    user of the arrival of mail in the specified file.

       MAILCHECK    This  parameter specifies how often (in seconds) the shell
		    will check for the arrival of mail in the files  specified
		    by	the  MAILPATH or MAIL parameters. The default value is
		    600 seconds (10 minutes). If set  to  0,  the  shell  will
		    check before each prompt.

       MAILPATH	    A colon-separated list of file names. If this parameter is
		    set, the shell informs the user of the arrival of mail  in
		    any of the specified files. Each file name can be followed
		    by % and a message that will be printed when the modifica‐
		    tion time changes. The default message is, you have mail.

       PS1	    Primary prompt string, by default " $ ".

       PS2	    Secondary prompt string, by default " > ".

       IFS	    Internal  field  separators, normally space, tab, and new‐
		    line (see Blank Interpretation section).

       SHACCT	    If this parameter is set to the name of a file writable by
		    the user, the shell will write an accounting record in the
		    file for each shell procedure executed.

       SHELL	    When the shell is invoked, it scans the  environment  (see
		    Environment section below) for this name.

       See  environ(5) for descriptions of the following environment variables
       that affect the execution of sh: LC_CTYPE and LC_MESSAGES.

       The shell gives default values to PATH, PS1, PS2, MAILCHECK,  and  IFS.
       Default values for HOME and MAIL are set by login(1).

   Blank Interpretation
       After  parameter	 and command substitution, the results of substitution
       are scanned for internal field separator	 characters  (those  found  in
       IFS) and split into distinct arguments where such characters are found.
       Explicit null arguments ("" or '') are retained.	 Implicit  null	 argu‐
       ments  (those  resulting	 from  parameters  that	 have  no  values) are
       removed.

   Input/Output Redirection
       A command's input and output may be redirected using a special notation
       interpreted  by	the shell. The following may appear anywhere in a sim‐
       ple-command or may precede or follow a command and are not passed on as
       arguments to the invoked command. Note: Parameter and command substitu‐
       tion occurs before word or digit is used.

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

       >word	       Use file word as standard output (file  descriptor  1).
		       If  the	file does not exist, it is created; otherwise,
		       it is truncated to zero length.

       >>word	       Use file word as standard output. If the	 file  exists,
		       output  is  appended to it by first seeking to the EOF.
		       Otherwise, the file is created.

       <>word	       Open file word for  reading  and	 writing  as  standard
		       input.

       <<[−]word       After  parameter	 and  command  substitution is done on
		       word, the shell input is read up to the first line that
		       literally matches the resulting word, or to an EOF. If,
		       however, the hyphen (−) is appended to <<:

			   1.	  leading tabs are stripped from  word	before
				  the shell input is read (but after parameter
				  and command substitution is done on word);

			   2.	  leading tabs are  stripped  from  the	 shell
				  input	 as it is read and before each line is
				  compared with word; and

			   3.	  shell input is read up  to  the  first  line
				  that	literally  matches the resulting word,
				  or to an EOF.
		       If any character of word is quoted (see Quoting section
		       later),	no  additional processing is done to the shell
		       input. If no characters of word are quoted:

			   1.	  parameter and command substitution occurs;

			   2.	  (escaped) \newlines are removed; and

			   3.	  \ must be used to quote the characters \, $,
				  and `.
		       The resulting document becomes the standard input.

       <&digit	       Use  the	 file associated with file descriptor digit as
		       standard input. Similarly for the standard output using
		       >&digit.

       <&−	       The  standard  input is closed. Similarly for the stan‐
		       dard output using >&−.

       If any of the above is preceded by a digit, the file  descriptor	 which
       will  be	 associated  with  the	file  is  that	specified by the digit
       (instead of the default 0 or 1). For example:

	 ... 2>&1

       associates file descriptor 2 with the file  currently  associated  with
       file descriptor 1.

       The order in which redirections are specified is significant. The shell
       evaluates redirections left-to-right. For example:

	 ... 1>xxx 2>&1

       first associates file descriptor 1 with file xxx.  It  associates  file
       descriptor  2 with the file associated with file descriptor 1 (that is,
       xxx). If the order of redirections were	reversed,  file	 descriptor  2
       would  be  associated with the terminal (assuming file descriptor 1 had
       been) and file descriptor 1 would be associated with file xxx.

       Using the terminology introduced on the first page, under Commands,  if
       a  command  is composed of several simple commands, redirection will be
       evaluated for the entire command before it is evaluated for each simple
       command.	 That is, the shell evaluates redirection for the entire list,
       then each pipeline within the list, then each command within each pipe‐
       line, then each list within each command.

       If  a command is followed by &, the default standard input for the com‐
       mand is the empty file, /dev/null. Otherwise, the environment  for  the
       execution  of  a	 command contains the file descriptors of the invoking
       shell as modified by input/output specifications.

   File Name Generation
       Before a command is executed, each command  word	 is  scanned  for  the
       characters  *, ?, and [. If one of these characters appears the word is
       regarded as a pattern. The word is replaced with alphabetically	sorted
       file  names  that  match	 the  pattern.	If  no file name is found that
       matches the pattern, the word is left unchanged. The character . at the
       start of a file name or immediately following a /, as well as the char‐
       acter / itself, must be matched explicitly.

       *	    Matches any string, including the null string.

       ?	    Matches any single character.

       [...]	    Matches any one of the  enclosed  characters.  A  pair  of
		    characters	separated by − matches any character lexically
		    between the pair, inclusive. If the first  character  fol‐
		    lowing the opening [ is a !, any character not enclosed is
		    matched.

       Notice that all quoted characters (see below) must be  matched  explic‐
       itly in a filename.

   Quoting
       The  following characters have a special meaning to the shell and cause
       termination of a word unless quoted:

       ;  &  (	)  |  ^	 <  >  newline	space  tab

       A character may be quoted (that is, made to stand for itself)  by  pre‐
       ceding  it with a backslash (\) or inserting it between a pair of quote
       marks ('' or ""). During processing, the shell may quote certain	 char‐
       acters  to  prevent  them from taking on a special meaning. Backslashes
       used to quote a single character are removed from the word  before  the
       command	is  executed.  The pair \newline is removed from a word before
       command and parameter substitution.

       All characters enclosed between a pair  of  single  quote  marks	 (''),
       except  a  single quote, are quoted by the shell. Backslash has no spe‐
       cial meaning inside a pair of single quotes.  A	single	quote  may  be
       quoted  inside  a  pair of double quote marks (for example, "'"), but a
       single quote can not be quoted inside a pair of single quotes.

       Inside a pair of double quote marks (""), parameter and command substi‐
       tution occurs and the shell quotes the results to avoid blank interpre‐
       tation and file name generation. If $*  is  within  a  pair  of	double
       quotes, the positional parameters are substituted and quoted, separated
       by quoted spaces ("$1 $2 ..."). However, if $@ is within a pair of dou‐
       ble quotes, the positional parameters are substituted and quoted, sepa‐
       rated by unquoted spaces ("$1""$2"  ... ). \ quotes the	characters  \,
       `,  , (comma), and $. The pair \newline is removed before parameter and
       command substitution. If a backslash precedes characters other than  \,
       `,  ,  (comma),	$, and newline, then the backslash itself is quoted by
       the shell.

   Prompting
       When used interactively, the shell prompts with the value of PS1 before
       reading	a command. If at any time a newline is typed and further input
       is needed to complete a command, the secondary  prompt  (that  is,  the
       value of PS2) is issued.

   Environment
       The  environment (see environ(5)) is a list of name-value pairs that is
       passed to an executed program in the same  way  as  a  normal  argument
       list.  The  shell  interacts  with  the environment in several ways. On
       invocation, the shell scans the environment and creates a parameter for
       each  name  found, giving it the corresponding value. If the user modi‐
       fies the value of any of these parameters or  creates  new  parameters,
       none of these affects the environment unless the export command is used
       to bind the shell's parameter to the environment (see also set  -a).  A
       parameter  may  be removed from the environment with the unset command.
       The environment seen by any executed command is thus  composed  of  any
       unmodified  name-value  pairs  originally inherited by the shell, minus
       any pairs removed by unset, plus any modifications or additions, all of
       which must be noted in export commands.

       The environment for any simple-command may be augmented by prefixing it
       with one or more assignments to parameters. Thus:

	 TERM=450  command

       and

	 (export TERM; TERM=450;   command

       are equivalent as far as the execution of command is concerned if  com‐
       mand is not a Special Command. If command is a Special Command, then

	 TERM=450   command

       will modify the TERM variable in the current shell.

       If the -k flag is set, all keyword arguments are placed in the environ‐
       ment, even if they occur after the command name. The following  example
       first prints a=b c and c:

	 echo a=b  c

	 a=b  c

	 set  −k

	 echo a=b  c

	 c

   Signals
       The  INTERRUPT  and  QUIT signals for an invoked command are ignored if
       the command is followed by &. Otherwise, signals have the values inher‐
       ited by the shell from its parent, with the exception of signal 11 (but
       see also the trap command below).

   Execution
       Each time a command is executed, the  command  substitution,  parameter
       substitution, blank interpretation, input/output redirection, and file‐
       name generation listed above are	 carried  out.	If  the	 command  name
       matches the name of a defined function, the function is executed in the
       shell process (note how this differs from the execution of shell script
       files,  which  require a sub-shell for invocation). If the command name
       does not match the name of a defined function, but matches one  of  the
       Special Commands listed below, it is executed in the shell process.

       The  positional	parameters $1, $2, ... are set to the arguments of the
       function. If the command name matches neither a Special Command nor the
       name  of a defined function, a new process is created and an attempt is
       made to execute the command via exec(2).

       The shell parameter PATH defines the search path for the directory con‐
       taining	the  command.  Alternative  directory names are separated by a
       colon (:). The default path is /usr/bin. The current directory is spec‐
       ified by a null path name, which can appear immediately after the equal
       sign, between two colon delimiters anywhere in the path list, or at the
       end  of the path list. If the command name contains a / the search path
       is not used. Otherwise, each directory in the path is searched  for  an
       executable  file.   If  the  file  has execute permission but is not an
       a.out file, it is assumed to be a file  containing  shell  commands.  A
       sub-shell  is  spawned to read it. A parenthesized command is also exe‐
       cuted in a sub-shell.

       The location in the search path where a command was found is remembered
       by  the	shell  (to help avoid unnecessary execs later). If the command
       was found in a relative directory, its location must  be	 re-determined
       whenever	 the  current  directory changes. The shell forgets all remem‐
       bered locations whenever the PATH variable is changed or	 the  hash  -r
       command is executed (see below).

   Special Commands
       Input/output  redirection  is  now  permitted  for these commands. File
       descriptor 1 is the  default  output  location.	When  Job  Control  is
       enabled,	 additional Special Commands are added to the shell's environ‐
       ment (see Job Control section below).

       :

	   No effect; the command does nothing. A zero exit code is returned.

       . filename

	   Read and execute commands from filename and return. The search path
	   specified  by  PATH	is used to find the directory containing file‐
	   name.

       bg [%jobid ...]

	   When Job Control is enabled, the bg command is added to the	user's
	   environment	to manipulate jobs. Resumes the execution of a stopped
	   job in the background. If %jobid is	omitted	 the  current  job  is
	   assumed. (See Job Control section below for more detail.)

       break [ n ]

	   Exit	 from  the enclosing for or while loop, if any. If n is speci‐
	   fied, break n levels.

       cd [ argument ]

	   Change the current directory to argument. The shell parameter  HOME
	   is  the  default  argument.	The shell parameter CDPATH defines the
	   search path for the	directory  containing  argument.   Alternative
	   directory  names  are separated by a colon (:). The default path is
	   <null> (specifying the current directory). Note: The current direc‐
	   tory is specified by a null path name, which can appear immediately
	   after the equal sign or between the colon delimiters anywhere  else
	   in  the  path  list. If argument begins with a / the search path is
	   not used. Otherwise, each directory in the  path  is	 searched  for
	   argument.

       chdir [ dir ]

	   chdir changes the shell's working directory to directory dir. If no
	   argument is given, change to the home directory of the user. If dir
	   is  a  relative  pathname not found in the current directory, check
	   for it in those directories listed in the CDPATH variable.  If  dir
	   is the name of a shell variable whose value starts with a /, change
	   to the directory named by that value.

       continue [ n ]

	   Resume the next iteration of the enclosing for or while loop. If  n
	   is specified, resume at the n-th enclosing loop.

       echo [ arguments ... ]

	   The	words in arguments are written to the shell's standard output,
	   separated by space characters. See echo(1)  for  fuller  usage  and
	   description.

       eval [ argument ... ]

	   The arguments are read as input to the shell and the resulting com‐
	   mand(s) executed.

       exec [ argument ... ]

	   The command specified by the arguments is executed in place of this
	   shell  without  creating  a new process. Input/output arguments may
	   appear and, if no  other  arguments	are  given,  cause  the	 shell
	   input/output to be modified.

       exit [ n ]

	   Causes the calling shell or shell script to exit with the exit sta‐
	   tus specified by n. If n is omitted the exit status is that of  the
	   last command executed (an EOF will also cause the shell to exit.)

       export [ name ... ]

	   The	given names are marked for automatic export to the environment
	   of subsequently executed commands. If no arguments are given, vari‐
	   able	 names	that  have  been  marked for export during the current
	   shell's execution are listed.  (Variable names exported from a par‐
	   ent	shell  are listed only if they have been exported again during
	   the current shell's execution.) Function names are not exported.

       fg [%jobid ...]

	   When Job Control is enabled, the fg command is added to the	user's
	   environment	to manipulate jobs. This command resumes the execution
	   of a stopped job in the foreground  and  also  moves	 an  executing
	   background  job into the foreground. If %jobid is omitted, the cur‐
	   rent job is assumed.	 (See  Job  Control  section  below  for  more
	   detail.)

       getopts

	   Use	in  shell  scripts  to	support	 command syntax standards (see
	   intro(1)). This command parses positional parameters and checks for
	   legal options.  See getoptcvt(1) for usage and description.

       hash [ -r ] [ name ... ]

	   For each name, the location in the search path of the command spec‐
	   ified by name is determined and remembered by  the  shell.  The  -r
	   option  causes  the shell to forget all remembered locations. If no
	   arguments are given, information about remembered commands is  pre‐
	   sented.  Hits  is the number of times a command has been invoked by
	   the shell process. Cost is a measure of the work required to locate
	   a  command  in the search path. If a command is found in a relative
	   directory in the search path, after changing to that directory, the
	   stored location of that command is recalculated. Commands for which
	   this will be done are indicated by an asterisk (*) adjacent to  the
	   hits	 information.  Cost will be incremented when the recalculation
	   is done.

       jobs [-p|-l] [%jobid ...]
       jobs -x command [arguments]

	   Reports all jobs that are stopped or executing in  the  background.
	   If  %jobid  is omitted, all jobs that are stopped or running in the
	   background will be reported. (See Job  Control  section  below  for
	   more detail.)

       kill [ -sig ] %job ...
       kill -l

	   Sends either the TERM (terminate) signal or the specified signal to
	   the specified jobs or processes. Signals are either given by number
	   or  by  names  (as  given in signal.h(3HEAD) stripped of the prefix
	   "SIG" with the exception that SIGCHD is named CHLD). If the	signal
	   being  sent	is  TERM  (terminate) or HUP (hangup), then the job or
	   process will be sent a CONT (continue) signal if it is stopped. The
	   argument  job can be the process id of a process that is not a mem‐
	   ber of one of the active jobs. See Job Control section below for  a
	   description	of the format of job. In the second form, kill -l, the
	   signal numbers and names are listed. (See kill(1)).

       login [ argument ... ]

	   Equivalent to `exec login argument....' See login(1) for usage  and
	   description.

       newgrp [ argument ]

	   Equivalent  to  exec	 newgrp	 argument. See newgrp(1) for usage and
	   description.

       pwd

	   Print the current working  directory.  See  pwd(1)  for  usage  and
	   description.

       read name ...

	   One	line  is  read from the standard input and, using the internal
	   field separator, IFS (normally  space  or  tab),  to	 delimit  word
	   boundaries,	the first word is assigned to the first name, the sec‐
	   ond word to the second name, and  so	 forth,	 with  leftover	 words
	   assigned  to	 the last name. Lines can be continued using \newline.
	   Characters other than newline can be quoted by preceding them  with
	   a  backslash.  These	 backslashes  are  removed  before  words  are
	   assigned to names, and no interpretation is done on	the  character
	   that	 follows the backslash. The return code is 0, unless an EOF is
	   encountered.

       readonly [ name ... ]

	   The given names are marked readonly and the	values	of  the	 these
	   names  may not be changed by subsequent assignment. If no arguments
	   are given, a list of all readonly names is printed.

       return [ n ]

	   Causes a function to exit with the return value specified by n.  If
	   n  is  omitted,  the return status is that of the last command exe‐
	   cuted.

       set [ -aefhkntuvx [ argument ... ] ]

	   -a	 Mark variables which are modified or created for export.

	   -e	 Exit immediately if a command exits with a non-zero exit sta‐
		 tus.

	   -f	 Disable file name generation.

	   -h	 Locate	 and  remember	function  commands  as	functions  are
		 defined (function commands  are  normally  located  when  the
		 function is executed).

	   -k	 All  keyword  arguments  are  placed in the environment for a
		 command, not just those that precede the command name.

	   -n	 Read commands but do not execute them.

	   -t	 Exit after reading and executing one command.

	   -u	 Treat unset variables as an error when substituting.

	   -v	 Print shell input lines as they are read.

	   -x	 Print commands and their arguments as they are executed.

	   -	 Do not change any of the flags; useful in setting $1 to −.

	   Using + rather than − causes these flags to be  turned  off.	 These
	   flags  can  also  be used upon invocation of the shell. The current
	   set of flags may be found in $−. The remaining arguments are	 posi‐
	   tional  parameters and are assigned, in order, to $1, $2, ... If no
	   arguments are given, the values of all names are printed.

       shift [ n ]

	   The positional parameters from $n+1 ... are renamed $1 ... .	 If  n
	   is not given, it is assumed to be 1.

       stop pid ...

	   Halt execution of the process number pid. (see ps(1)).

       suspend

	   Stops  the  execution  of  the  current shell (but not if it is the
	   login shell).

       test

	   Evaluate  conditional  expressions.	See  test(1)  for  usage   and
	   description.

       times

	   Print  the accumulated user and system times for processes run from
	   the shell.

       trap [ argument n [ n2 ... ]]

	   The command argument is to be read  and  executed  when  the	 shell
	   receives  numeric  or  symbolic  signal(s)  (n). (Note: argument is
	   scanned once when the trap is set and once when the trap is taken.)
	   Trap commands are executed in order of signal number or correspond‐
	   ing symbolic names. Any attempt to set a trap on a signal that  was
	   ignored on entry to the current shell is ineffective. An attempt to
	   trap on signal 11 (memory fault) produces an error. If argument  is
	   absent,  all trap(s) n are reset to their original values. If argu‐
	   ment is the null string, this signal is ignored by the shell and by
	   the	commands  it  invokes. If n is 0, the command argument is exe‐
	   cuted on exit from the shell. The trap command  with	 no  arguments
	   prints a list of commands associated with each signal number.

       type [ name ... ]

	   For	each  name,  indicate how it would be interpreted if used as a
	   command name.

       ulimit [ [-HS] [-a | -cdfnstv] ]
       ulimit [ [-HS] [-c | -d | -f | -n | -s | -t | -v] ] limit

	   ulimit prints or sets hard or soft resource	limits.	 These	limits
	   are described in getrlimit(2).

	   If  limit  is  not present, ulimit prints the specified limits. Any
	   number of limits may be printed at one time. The -a	option	prints
	   all limits.

	   If  limit is present, ulimit sets the specified limit to limit. The
	   string unlimited requests the largest valid limit.  Limits  may  be
	   set	for only one resource at a time. Any user may set a soft limit
	   to any value below the hard limit. Any user may lower a hard limit.
	   Only a super-user may raise a hard limit. (See su(1M).)

	   The	-H  option  specifies  a hard limit. The -S option specifies a
	   soft limit. If neither option is specified, ulimit  will  set  both
	   limits and print the soft limit.

	   The	following  options specify the resource whose limits are to be
	   printed or set. If no option is specified, the file size  limit  is
	   printed or set.

	   -c	 maximum core file size (in 512-byte blocks)

	   -d	 maximum size of data segment or heap (in kbytes)

	   -f	 maximum file size (in 512-byte blocks)

	   -n	 maximum file descriptor plus 1

	   -s	 maximum size of stack segment (in kbytes)

	   -t	 maximum CPU time (in seconds)

	   -v	 maximum size of virtual memory (in kbytes)

	   Run	the  sysdef(1M)	 command to obtain the maximum possible limits
	   for your system.  The values reported are in hexadecimal,  but  can
	   be  translated  into	 decimal numbers using the bc(1) utility.  See
	   swap(1M).)

	   As an example of ulimit, to limit the size of a core file dump to 0
	   Megabytes, type the following:

	     ulimit -c 0

       umask [ nnn ]

	   The user file-creation mask is set to nnn (see umask(1)). If nnn is
	   omitted, the current value of the mask is printed.

       unset [ name ... ]

	   For each name, remove the corresponding variable or function value.
	   The variables PATH, PS1, PS2, MAILCHECK, and IFS cannot be unset.

       wait [ n ]

	   Wait	 for  your background process whose process id is n and report
	   its termination status. If n is omitted, all your shell's currently
	   active background processes are waited for and the return code will
	   be zero.

   Invocation
       If the shell is invoked through exec(2)	and  the  first	 character  of
       argument	 zero  is −, commands are initially read from /etc/profile and
       from $HOME/.profile, if such files exist. Thereafter, commands are read
       as described below, which is also the case when the shell is invoked as
       /usr/bin/sh. The flags below are interpreted by the shell on invocation
       only.  Note:  Unless the -c or -s flag is specified, the first argument
       is assumed to be the name  of  a	 file  containing  commands,  and  the
       remaining arguments are passed as positional parameters to that command
       file:

       -c string      If the -c flag is present commands are read from string.

       -i	      If the -i flag is present or if the shell input and out‐
		      put  are	attached to a terminal, this shell is interac‐
		      tive. In this case, TERMINATE is ignored (so that kill 0
		      does  not	 kill  an  interactive shell) and INTERRUPT is
		      caught and ignored (so that wait is  interruptible).  In
		      all cases, QUIT is ignored by the shell.

       -p	      If  the  -p  flag is present, the shell will not set the
		      effective user and group IDs to the real user and	 group
		      IDs.

       -r	      If  the  -r  flag	 is  present the shell is a restricted
		      shell (see rsh(1M)).

       -s	      If the -s flag is present or  if	no  arguments  remain,
		      commands are read from the standard input. Any remaining
		      arguments specify the positional parameters. Shell  out‐
		      put  (except  for	 Special  Commands) is written to file
		      descriptor 2.

       The remaining flags and arguments are described under the  set  command
       above.

   Job Control (jsh)
       When the shell is invoked as jsh, Job Control is enabled in addition to
       all of the functionality described previously for  sh.  Typically,  Job
       Control	is  enabled  for  the  interactive shell only. Non-interactive
       shells typically do not benefit from the	 added	functionality  of  Job
       Control.

       With  Job Control enabled, every command or pipeline the user enters at
       the terminal is called a job. All jobs exist in one  of	the  following
       states:	foreground, background, or stopped. These terms are defined as
       follows:

	   1.	  A job in the foreground has read and	write  access  to  the
		  controlling terminal.

	   2.	  A job in the background is denied read access and has condi‐
		  tional  write	 access	 to  the  controlling  terminal	  (see
		  stty(1)).

	   3.	  A  stopped  job is a job that has been placed in a suspended
		  state, usually as a result of a  SIGTSTP  signal  (see  sig‐
		  nal.h(3HEAD)).

       Every  job that the shell starts is assigned a positive integer, called
       a job number which is tracked by the shell and will be used as an iden‐
       tifier  to indicate a specific job. Additionally, the shell keeps track
       of the current and previous jobs. The current job is  the  most	recent
       job  to be started or restarted. The previous job is the first non-cur‐
       rent job.

       The acceptable syntax for a Job Identifier is of the form:

       %jobid

       where jobid may be specified in any of the following formats:

       % or +	    For the current job.

       −	    For the previous job.

       ?<string>    Specify the job for which the command line	uniquely  con‐
		    tains string.

       n	    For job number n.

       pref	    Where  pref	 is  a	unique prefix of the command name. For
		    example, if the command ls -l name	were  running  in  the
		    background,	 it  could  be referred to as %ls. pref cannot
		    contain blanks unless it is quoted.

       When Job Control is enabled, the following commands are	added  to  the
       user's environment to manipulate jobs:

       bg [%jobid ...]

	   Resumes the execution of a stopped job in the background. If %jobid
	   is omitted the current job is assumed.

       fg [%jobid ...]

	   Resumes the execution of a stopped  job  in	the  foreground,  also
	   moves an executing background job into the foreground. If %jobid is
	   omitted the current job is assumed.

       jobs [-p|-l] [%jobid ...]
       jobs -x command [arguments]

	   Reports all jobs that are stopped or executing in  the  background.
	   If  %jobid  is omitted, all jobs that are stopped or running in the
	   background will  be	reported.  The	following  options  will  mod‐
	   ify/enhance the output of jobs:

	   -l	 Report	 the  process  group  ID  and working directory of the
		 jobs.

	   -p	 Report only the process group ID of the jobs.

	   -x	 Replace any jobid found in command or arguments with the cor‐
		 responding process group ID, and then execute command passing
		 it arguments.

       kill [ -signal ] %jobid

	   Builtin version of kill to provide the functionality	 of  the  kill
	   command for processes identified with a jobid.

       stop %jobid ...

	   Stops the execution of a background job(s).

       suspend

	   Stops  the  execution  of  the  current shell (but not if it is the
	   login shell).

       wait [%jobid ...]

	   wait builtin accepts a job identifier. If %jobid  is	 omitted  wait
	   behaves as described above under Special Commands.

   Large File Behavior
       See largefile(5) for the description of the behavior of sh and jsh when
       encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return  a non-zero exit status. If the shell is being used non-interac‐
       tively execution of the shell file is abandoned. Otherwise,  the	 shell
       returns the exit status of the last command executed (see also the exit
       command above).

   jsh Only
       If the shell is invoked as jsh and an attempt is made to exit the shell
       while there are stopped jobs, the shell issues one warning:

       There are stopped jobs.

       This  is	 the  only message. If another exit attempt is made, and there
       are still stopped jobs they will be sent a SIGHUP signal from the  ker‐
       nel and the shell is exited.

FILES
       $HOME/.profile

       /dev/null

       /etc/profile

       /tmp/sh*

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

   /usr/bin/sh, /usr/bin/jsh
       ┌─────────────────────────────┬─────────────────────────────┐
       │      ATTRIBUTE TYPE	     │	    ATTRIBUTE VALUE	   │
       ├─────────────────────────────┼─────────────────────────────┤
       │Availability		     │SUNWcsu			   │
       ├─────────────────────────────┼─────────────────────────────┤
       │CSI			     │Enabled			   │
       └─────────────────────────────┴─────────────────────────────┘

   /usr/xpg4/bin/sh
       ┌─────────────────────────────┬─────────────────────────────┐
       │      ATTRIBUTE TYPE	     │	    ATTRIBUTE VALUE	   │
       ├─────────────────────────────┼─────────────────────────────┤
       │Availability		     │SUNWxcu4			   │
       ├─────────────────────────────┼─────────────────────────────┤
       │CSI			     │Enabled			   │
       └─────────────────────────────┴─────────────────────────────┘

SEE ALSO
       intro(1), bc(1), echo(1), getoptcvt(1), kill(1), ksh(1), login(1), new‐
       grp(1), pfsh(1), pfexec(1), ps(1), pwd(1),  set(1),  shell_builtins(1),
       stty(1),	 test(1),  umask(1),  wait(1), rsh(1M), su(1M), swap(1M), sys‐
       def(1M), dup(2), exec(2), fork(2),  getrlimit(2),  pipe(2),  ulimit(2),
       setlocale(3C),  signal.h(3HEAD),	 passwd(4), profile(4), attributes(5),
       environ(5), largefile(5), XPG4(5)

WARNINGS
       The use of setuid shell scripts is strongly discouraged.

NOTES
       Words used for filenames in input/output	 redirection  are  not	inter‐
       preted  for  filename  generation  (see	File  Name  Generation section
       above). For example, cat file1 >a* will create a file named a*.

       Because commands in pipelines are run as separate processes,  variables
       set in a pipeline have no effect on the parent shell.

       If  the input or the output of a while or until loop is redirected, the
       commands in the loop are run in	a  sub-shell,  and  variables  set  or
       changed there have no effect on the parent process:

	    lastline=
	   while read line
	   do

		   lastline=$line
	   done < /etc/passwd
	   echo "lastline=$lastline"	   # lastline is empty!

       In these cases, the input or output can be redirected by using exec, as
       in the following example:

	    # Save standard input (file descriptor 0) as file
	   # descriptor 3, and redirect standard input from the file
	   /etc/passwd:

	   exec 3<&0		   # save standard input as fd 3
	   exec </etc/passwd	   # redirect input from file

	   lastline=
	   while read line
	   do
		   lastline=$line
	   done

	   exec 0<&3		   # restore standard input
	   exec 3<&-		   # close file descriptor 3
	   echo "$lastline"	   # lastline

       If you get the error message, "cannot fork, too	many  processes",  try
       using  the  wait(1)  command  to clean up your background processes. If
       this doesn't help, the system process table is  probably	 full  or  you
       have too many active foreground processes. There is a limit to the num‐
       ber of process ids associated with your login, and to  the  number  the
       system can keep track of.

       Only the last process in a pipeline can be waited for.

       If a command is executed, and a command with the same name is installed
       in a directory in the search path before the directory where the origi‐
       nal  command  was  found,  the shell will continue to exec the original
       command. Use the hash command to correct this situation.

       The Bourne shell has a limitation on the effective UID for  a  process.
       If  this	 UID  is  less	than 100 (and not equal to the real UID of the
       process), then the UID is reset to the real UID of the process.

       Because the shell implements both foreground and background jobs in the
       same  process  group, they all receive the same signals, which can lead
       to unexpected behavior. It is, therefore, recommended  that  other  job
       control shells be used, especially in an interactive environment.

       When  the shell executes a shell script that attempts to execute a non-
       existent command interpreter, the shell returns an erroneous diagnostic
       message that the shell script file does not exist.

SunOS 5.10			  2 May 2008				 sh(1)
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