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48 .TH WAIT 1 "Mar 13, 2008"
49 .SH NAME
50 wait \- await process completion
51 .SH SYNOPSIS
52 .LP
53 .nf
55 .fi
57 .SS "/bin/sh"
58 .LP
59 .nf
60 \fBwait\fR [\fIpid\fR]...
61 .fi
63 .SS "/bin/jsh /bin/ksh /usr/bin/sh"
64 .LP
65 .nf
66 \fBwait\fR [\fIpid\fR]...
67 .fi
69 .LP
70 .nf
71 \fBwait\fR [% \fIjobid\fR...]
72 .fi
74 .SS "/bin/csh"
75 .LP
76 .nf
77 \fBwait\fR
78 .fi
80 .SS "ksh93"
81 .LP
82 .nf
83 \fBwait\fR [\fIjob...\fR]
84 .fi
86 .SH DESCRIPTION
87 .sp
88 .LP
89 The shell itself executes \fBwait\fR, without creating a new process. If you
90 get the error message \fBcannot fork,too many processes\fR, try using the
91 \fBwait\fR command to clean up your background processes. If this doesn't help,
92 the system process table is probably full or you have too many active
93 foreground processes. There is a limit to the number of process \fBID\fRs
94 associated with your login, and to the number the system can keep track of.
95 .sp
96 .LP
97 Not all the processes of a pipeline with three or more stages are children of
98 the shell, and thus cannot be waited for.
99 .SS "/bin/sh, /bin/jsh"
100 .sp
101 .LP
102 Wait for your background process whose process \fBID\fR is \fIpid\fR and report
103 its termination status. If \fIpid\fR is omitted, all your shell's currently
104 active background processes are waited for and the return code is \fB0\fR. The
105 \fBwait\fR utility accepts a job identifier, when Job Control is enabled (jsh),
106 and the argument, \fIjobid\fR, is preceded by a percent sign (\fB%\fR).
107 .sp
108 .LP
109 If \fIpid\fR is not an active process \fBID,\fR the \fBwait\fR utility returns
110 immediately and the return code is \fB0\fR.
111 .SS "csh"
112 .sp
113 .LP
114 Wait for your background processes.
115 .SS "ksh"
116 .sp
117 .LP
118 When an asynchronous list is started by the shell, the process \fBID\fR of the
119 last command in each element of the asynchronous list becomes known in the
120 current shell execution environment.
121 .sp
122 .LP
123 If the \fBwait\fR utility is invoked with no operands, it waits until all
124 process \fBIDs\fR known to the invoking shell have terminated and exit with an
125 exit status of \fB0\fR.
126 .sp
127 .LP
128 If one or more \fIpid\fR or \fIjobid\fR operands are specified that represent
129 known process \fBID\fRs (or jobids), the \fBwait\fR utility waits until all of
130 them have terminated. If one or more \fIpid\fR or \fIjobid\fR operands are
131 specified that represent unknown process \fBID\fRs (or jobids), \fBwait\fR
132 treats them as if they were known process \fBID\fRs (or jobids) that exited
133 with exit status \fB127\fR. The exit status returned by the \fBwait\fR utility
134 is the exit status of the process requested by the last \fIpid\fR or
135 \fIjobid\fR operand.
136 .sp
137 .LP
138 The known process \fBID\fRs are applicable only for invocations of \fBwait\fR
139 in the current shell execution environment.
140 .SS "ksh93"
141 .sp
142 .LP
143 wait with no operands, waits until all jobs known to the invoking shell have
144 terminated. If one or more job operands are specified, wait waits until all of
145 them have completed. Each job can be specified as one of the following:
146 .sp
147 .ne 2
148 .na
149 \fB\fInumber\fR\fR
150 .ad
151 .RS 12n
152 \fInumber\fR refers to a process ID.
153 .RE
155 .sp
156 .ne 2
157 .na
158 \fB\fB-\fR\fInumber\fR\fR
159 .ad
160 .RS 12n
161 \fInumber\fR refers to a process group ID.
162 .RE
164 .sp
165 .ne 2
166 .na
167 \fB\fB%\fR\fInumber\fR\fR
168 .ad
169 .RS 12n
170 \fInumber\fR refers to a job number
171 .RE
173 .sp
174 .ne 2
175 .na
176 \fB\fB%\fR\fIstring\fR\fR
177 .ad
178 .RS 12n
179 Refers to a job whose name begins with \fIstring\fR
180 .RE
182 .sp
183 .ne 2
184 .na
185 \fB\fB%?\fR\fIstring\fR\fR
186 .ad
187 .RS 12n
188 Refers to a job whose name contains \fIstring\fR
189 .RE
191 .sp
192 .ne 2
193 .na
194 \fB\fB%+\fR\fR
195 .ad
196 .br
197 .na
198 \fB\fB%%\fR\fR
199 .ad
200 .RS 12n
201 Refers to the current job
202 .RE
204 .sp
205 .ne 2
206 .na
207 \fB\fB%-\fR\fR
208 .ad
209 .RS 12n
210 Refers to the previous job
211 .RE
213 .sp
214 .LP
215 If one ore more job operands is a process id or process group id not known by
216 the current shell environment, \fBwait\fR treats each of them as if it were a
217 process that exited with status 127.
218 .SH OPERANDS
219 .sp
220 .LP
221 The following operands are supported:
222 .sp
223 .ne 2
224 .na
225 \fB\fIpid\fR\fR
226 .ad
227 .RS 9n
228 The unsigned decimal integer process \fBID\fR of a command, for which the
229 utility is to wait for the termination.
230 .RE
232 .sp
233 .ne 2
234 .na
235 \fB\fIjobid\fR\fR
236 .ad
237 .RS 9n
238 A job control job \fBID\fR that identifies a background process group to be
239 waited for. The job control job \fBID\fR notation is applicable only for
240 invocations of \fBwait\fR in the current shell execution environment, and only
241 on systems supporting the job control option.
242 .RE
244 .SH USAGE
245 .sp
246 .LP
247 On most implementations, \fBwait\fR is a shell built-in. If it is called in a
248 subshell or separate utility execution environment, such as one of the
249 following,
250 .sp
251 .in +2
252 .nf
253 (wait)
254 nohup wait ...
255 find . -exec wait ... \e;
256 .fi
257 .in -2
258 .sp
260 .sp
261 .LP
262 it returns immediately because there is no known process \fBID\fRs to wait for
263 in those environments.
264 .SH EXAMPLES
265 .LP
266 \fBExample 1 \fRUsing A Script To Identify The Termination Signal
267 .sp
268 .LP
269 Although the exact value used when a process is terminated by a signal is
270 unspecified, if it is known that a signal terminated a process, a script can
271 still reliably figure out which signal is using \fBkill\fR, as shown by the
272 following (\fB/bin/ksh\fR and \fB/usr/bin/sh\fR):
274 .sp
275 .in +2
276 .nf
277 sleep 1000&
278 pid=$!
279 kill -kill $pid
280 wait $pid
281 echo $pid was terminated by a SIG$(kill -l $(($?\(mi128))) signal.
282 .fi
283 .in -2
284 .sp
286 .LP
287 \fBExample 2 \fRReturning The Exit Status Of A Process
288 .sp
289 .LP
290 If the following sequence of commands is run in less than 31 seconds
291 (\fB/bin/ksh\fR and \fB/usr/bin/sh\fR):
293 .sp
294 .in +2
295 .nf
296 sleep 257 | sleep 31 &
298 jobs -l %%
299 .fi
300 .in -2
301 .sp
303 .sp
304 .LP
305 then either of the following commands returns the exit status of the second
306 \fBsleep\fR in the pipeline:
308 .sp
309 .in +2
310 .nf
311 wait <\fIpid of sleep 31\fR>
312 wait %%
313 .fi
314 .in -2
315 .sp
317 .SH ENVIRONMENT VARIABLES
318 .sp
319 .LP
320 See \fBenviron\fR(5) for descriptions of the following environment variables
321 that affect the execution of \fBwait\fR: \fBLANG\fR, \fBLC_ALL\fR,
322 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
323 .SH EXIT STATUS
324 .SS "ksh93"
325 .sp
326 .LP
327 The following exit values are returned by the \fBwait\fR built-in in
328 \fBksh93\fR:
329 .sp
330 .ne 2
331 .na
332 \fB\fB0\fR\fR
333 .ad
334 .RS 7n
335 \fBwait\fR was invoked with no operands. All processes known by the invoking
336 process have terminated.
337 .RE
339 .sp
340 .ne 2
341 .na
342 \fB\fB127\fR\fR
343 .ad
344 .RS 7n
345 \fIjob\fR is a process id or process group id that is unknown to the current
346 shell environment.
347 .RE
349 .SH ATTRIBUTES
350 .sp
351 .LP
352 See \fBattributes\fR(5) for descriptions of the following attributes:
353 .sp
355 .sp
356 .TS
357 box;
358 c | c
359 l | l .
360 ATTRIBUTE TYPE ATTRIBUTE VALUE
361 _
362 Interface Stability Committed
363 _
364 Standard See \fBstandards\fR(5).
365 .TE
367 .SH SEE ALSO
368 .sp
369 .LP
370 \fBcsh\fR(1), \fBjobs\fR(1), \fBksh\fR(1), \fBksh93\fR(1), \fBsh\fR(1),
371 \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)