wait - Awaits process completion
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.
Interfaces documented on this reference page conform to industry standards as follows:
wait: XPG4, XPG4-UNIX
Refer to the
reference page for more information
about industry standards and associated tags.
One of the following:
The unsigned decimal integer process ID of a command, for
which the utility is to wait for the termination.
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
is determined by the last command in the
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
in the current shell execution environment.
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:
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
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
utility exits with one of the following values:
utility was invoked with no operands
and all process IDs known by the invoking shell have terminated.
utility detected an error.
The command identified by the last
operand specified is unknown.
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:
The following environment variables affect the execution of
Provides a default value for the internationalization variables
that are unset or null. If
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.
If set to a non-empty string value, overrides the values of
all the other internationalization variables.
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).
Determines the locale used to affect the format and contents
of diagnostic messages written to standard error.
Determines the location of message catalogues for the processing
Commands: bg(1), csh(1), fg(1), jobs(1), kill(1), ksh(1), sh(1)