User Commands wait(1)
NAME
wait - await process completion
SYNOPSIS
/bin/sh
wait [pid]...
/bin/jsh /bin/ksh /usr/xpg4/bin/sh
wait [pid]...
wait [% jobid...]
/bin/csh
wait
ksh93
wait [job...]
DESCRIPTION
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
for.
/bin/sh, /bin/jsh
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 is 0. The wait utility accepts a job
identifier, when Job Control is enabled (jsh), and the argu-
ment, jobid, is preceded by a percent sign (%).
If pid is not an active process ID, the wait utility returns
immediately and the return code is 0.
SunOS 5.11 Last change: 13 Mar 2008 1
User Commands wait(1)
csh
Wait for your background processes.
ksh
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
environment.
If the wait utility is invoked with no operands, it waits
until all process IDs known to the invoking shell have ter-
minated 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
waits until all of them have terminated. If one or more pid
or jobid operands are specified that represent unknown pro-
cess IDs (or jobids), wait treats them as if they were known
process IDs (or jobids) 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 or jobid
operand.
The known process IDs are applicable only for invocations of
wait in the current shell execution environment.
ksh93
wait with no operands, waits until all jobs known to the
invoking shell have terminated. If one or more job operands
are specified, wait waits until all of them have completed.
Each job can be specified as one of the following:
number number refers to a process ID.
-number number refers to a process group ID.
%number number refers to a job number
%string Refers to a job whose name begins with string
%?string Refers to a job whose name contains string
%]
%%
SunOS 5.11 Last change: 13 Mar 2008 2
User Commands wait(1)
Refers to the current job
%- Refers to the previous job
If one ore more job operands is a process id or process
group id not known by the current shell environment, wait
treats each of them as if it were a process that exited with
status 127.
OPERANDS
The following operands are supported:
pid The unsigned decimal integer process ID of a com-
mand, for which the utility is to wait for the ter-
mination.
jobid 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,
and only on systems supporting the job control
option.
USAGE
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,
(wait)
nohup wait ...
find . -exec wait ... \;
it returns immediately because there is no known process IDs
to wait for in those environments.
EXAMPLES
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):
SunOS 5.11 Last change: 13 Mar 2008 3
User Commands wait(1)
sleep 1000&
pid=$!
kill -kill $pid
wait $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 returns the exit
status of the second sleep in the pipeline:
wait
wait %%
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of wait: LANG, LCAL,
LCTYPE, LCMESAGES, and NLSPATH.
EXIT STATUS
ksh93
The following exit values are returned by the wait built-in
in ksh93:
0 wait was invoked with no operands. All processes
known by the invoking process have terminated.
127 job is a process id or process group id that is
unknown to the current shell environment.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
SunOS 5.11 Last change: 13 Mar 2008 4
User Commands wait(1)
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
Interface Stability Committed
Standard See standards(5).
SEE ALSO
csh(1), jobs(1), ksh(1), ksh93(1), sh(1), attributes(5),
environ(5), standards(5)
SunOS 5.11 Last change: 13 Mar 2008 5
|
