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wait(1)
NAME
  wait - Awaits process completion

SYNOPSIS
  wait [pid]

				     Note

       The C shell has a built-in version of the wait command.	If you are
       using the C shell, and want to guarantee that you are using the
       command described here, you must specify the full path /usr/bin/wait.
       See the csh(1) reference page for a description of the built-in
       command.

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  wait:	 XPG4, XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

OPTIONS
  None

OPERANDS
  pid One of the following:

       1.
	The unsigned decimal integer process ID of a command, for which the
	utility is to wait for the termination.

       2.
	A job control job ID that identifies a background process group to be
	waited for. The job control job ID notation is applicable only for
	invocations of wait in the current shell execution environment.	 The
	exit status of wait is determined by the last command in the
	pipeline.

DESCRIPTION
  When an asynchronous list is started by the shell, the process ID of the
  last command in each element of the asynchronous list becomes known in the
  current shell execution environment.

  If the wait utility is invoked with no operands, it waits until all process
  IDs known to the invoking shell have terminated and exits with a zero exit
  status.

  If one or more pid operands are specified that represent known process IDs,
  the wait utility waits until all of them have terminated. If one or more
  pid operands are specified that represent unknown process IDs, wait treats
  them as if they were known process IDs that exited with exit status 127.
  The exit status returned by the wait utility is the exit status of the
  process requested by the last pid operand.

  The known process IDs are applicable only for invocations of wait in the
  current shell execution environment.

RESTRICTIONS
   1.  If wait is called in a subshell or separate utility execution
       environment, such as one of the following, it returns immediately
       because there are no known process IDs to wait for in those
       environments:


	    (wait)
	    nohup wait ...
	    find . -exec wait ... \;

   2.  If the exit status of wait is greater than 128, there is no way for
       the application to know if the waited-for process exited with that
       value or was killed by a signal.	 Since most utilities exit with small
       values, there is seldom any ambiguity.

EXIT STATUS
  If one or more parameters were specified, all of them have terminated or
  were not known by the invoking shell, and the status of the last parameter
  specified is known, then the exit status of wait is the exit status
  information of the command indicated by the last parameter specified.	 If
  the process terminated abnormally due to the receipt of a signal, the exit
  status is greater than 128 and is distinct from the exit status generated
  by other signals.  (See the kill -l option.) Otherwise, the wait utility
  exits with one of the following values:

  0   The wait utility was invoked with no operands and all process IDs known
      by the invoking shell have terminated.

  1-126
      The wait utility detected an error.

  127 The command identified by the last pid operand specified is unknown.

EXAMPLES
   1.  Although the exact value used when a process is terminated by a signal
       is unspecified, if it is known that a signal terminated a process, a
       script can still reliably figure out which signal using kill as shown
       by the following script:


	    sleep 1000&
	    pid=$!
	    kill -kill $pid
	    wait $pid
	    echo $pid was terminated by a SIG$(kill -l $?) signal.

   2.  If either sequence of commands shown on the first two lines is run in
       less than 31 seconds either of the commands shown on lines 3 and 4
       will return the exit status of the second sleep in the pipeline:


	    sleep 257 | sleep 31 &
	    jobs -l %%
	    wait <pid of sleep 31>
	    wait %%



ENVIRONMENT VARIABLES
  The following environment variables affect the execution of wait:

  LANG
      Provides a default value for the internationalization variables that
      are unset or null. If LANG is unset or null, the corresponding value
      from the default locale is used.	If any of the internationalization
      variables contain an invalid setting, the utility behaves as if none of
      the variables had been defined.

  LC_ALL
      If set to a non-empty string value, overrides the values of all the
      other internationalization variables.

  LC_CTYPE
      Determines the locale for the interpretation of sequences of bytes of
      text data as characters (for example, single-byte as opposed to
      multibyte characters in arguments).

  LC_MESSAGES
      Determines the locale used to affect the format and contents of
      diagnostic messages written to standard error.

  NLSPATH
      Determines the location of message catalogues for the processing of
      LC_MESSAGES.

SEE ALSO
  Commands:  bg(1), csh(1), fg(1), jobs(1), kill(1), ksh(1), sh(1)

  Functions:  wait(2)

  Standards:  standards(5)