wait - await process completion
/bin/jsh /bin/ksh /usr/xpg4/bin/sh
wait [ % jobid...]
The shell itself executes wait, without creating a new pro-
cess. If you get the error message cannot fork,too many
processes, try using the wait command to clean up your back-
ground processes. If this doesn't help, the system process
table is probably full or you have too many active fore-
ground processes. There is a limit to the number of process
IDs associated with your login, and to the number the system
can keep track of.
Not all the processes of a pipeline with three or more
stages are children of the shell, and thus cannot be waited
Wait for your background process whose process ID is pid and
report its termination status. If pid is omitted, all your
shell's currently active background processes are waited for
and the return code will be 0. The wait utility accepts a
job identifier, when Job Control is enabled (jsh), and the
argument, jobid, is preceded by a percent sign (%).
If pid is not an active process ID, the wait utility will
return immediately and the return code will be 0.
Wait for your background processes.
When an asynchronous list is started by the shell, the pro-
cess ID of the last command in each element of the asynchro-
nous list becomes known in the current shell execution
If the wait utility is invoked with no operands, it will
wait until all process IDs known to the invoking shell have
terminated and exit with an exit status of 0.
If one or more pid or jobid operands are specified that
represent known process IDs (or jobids), the wait utility
will wait until all of them have terminated. If one or more
pid or jobid operands are specified that represent unknown
process IDs (or jobids), wait will treat them as if they
were known process IDs (or jobids) that exited with exit
status 127. The exit status returned by the wait utility
will be the exit status of the process requested by the last
pid or jobid operand.
The known process IDs are applicable only for invocations of
wait in the current shell execution environment.
The following operands are supported:
One of the following:
pid The unsigned decimal integer process ID of a command,
for which the utility is to wait for the termination.
jobid A job control job ID that identifies a background pro-
cess group to be waited for. The job control job ID
notation is applicable only for invocations of wait in
the current shell execution environment, and only on
systems supporting the job control option.
On most implementations, wait is a shell built-in. If it is
called in a subshell or separate utility execution environ-
ment, such as one of the following,
nohup wait ...
find . -exec wait ... \;
it will return immediately because there will be no known
process IDs to wait for in those environments.
Example 1: Using A Script To Identify The Termination Signal
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 is using kill, as shown by the following
(/bin/ksh and /usr/xpg4/bin/sh):
kill -kill $pid
echo $pid was terminated by a SIG$(kill -l $(($?-128))) signal.
Example 2: Returning The Exit Status Of A Process
If the following sequence of commands is run in less than 31
seconds (/bin/ksh and /usr/xpg4/bin/sh):
sleep 257 | sleep 31 &
jobs -l %%
then either of the following commands will return the exit
status of the second sleep in the pipeline:
wait <pid of sleep 31>
See environ(5) for descriptions of the following environment
variables that affect the execution of wait: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWcsu |
| Interface Stability | Standard |
csh(1), jobs(1), ksh(1), sh(1), attributes(5), environ(5),
Man(1) output converted with