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28 .\" @(#)wait.2 8.2 (Berkeley) 4/19/94
39 .Nd wait for process termination
46 .Fn wait "int *status"
50 .Fn waitpid "pid_t wpid" "int *status" "int options"
52 .Fn wait3 "int *status" "int options" "struct rusage *rusage"
54 .Fn wait4 "pid_t wpid" "int *status" "int options" "struct rusage *rusage"
58 function suspends execution of its calling process until
60 information is available for a terminated child process,
61 or a signal is received.
62 On return from a successful
67 area contains termination information about the process that exited
72 system call provides a more general interface for programs
73 that need to wait for certain child processes,
74 that need resource utilization statistics accumulated by child processes,
75 or that require options.
76 The other wait functions are implemented using
81 argument specifies the set of child processes for which to wait.
84 is -1, the call waits for any child process.
88 the call waits for any child process in the process group of the caller.
91 is greater than zero, the call waits for the process with process id
95 is less than -1, the call waits for any process whose process group id
96 equals the absolute value of
101 argument is defined below.
105 argument contains the bitwise OR of any of the following options.
108 option indicates that children of the current process that
109 have continued from a job control stop, by receiving a
111 signal, should also have their status reported.
115 is used to indicate that the call should not block if
116 there are no processes that wish to report status.
120 children of the current process that are stopped
122 .Dv SIGTTIN , SIGTTOU , SIGTSTP ,
125 signal also have their status reported.
128 option is an alias for
132 option keeps the process whose status is returned in a waitable state.
133 The process may be waited for again after this call completes.
137 is non-zero, a summary of the resources used by the terminated
139 children is returned (this information is currently not available
140 for stopped or continued processes).
144 option is specified and no processes
145 wish to report status,
153 function is identical to
166 The following macros may be used to test the manner of exit of the process.
167 One of the first three macros will evaluate to a non-zero (true) value:
169 .It Fn WIFCONTINUED status
170 True if the process has not terminated, and
171 has continued after a job control stop.
172 This macro can be true only if the wait call specified the
175 .It Fn WIFEXITED status
176 True if the process terminated normally by a call to
180 .It Fn WIFSIGNALED status
181 True if the process terminated due to receipt of a signal.
182 .It Fn WIFSTOPPED status
183 True if the process has not terminated, but has stopped and can be restarted.
184 This macro can be true only if the wait call specified the
187 or if the child process is being traced (see
191 Depending on the values of those macros, the following macros
192 produce the remaining status information about the child process:
194 .It Fn WEXITSTATUS status
197 is true, evaluates to the low-order 8 bits
198 of the argument passed to
203 .It Fn WTERMSIG status
205 .Fn WIFSIGNALED status
206 is true, evaluates to the number of the signal
207 that caused the termination of the process.
208 .It Fn WCOREDUMP status
210 .Fn WIFSIGNALED status
211 is true, evaluates as true if the termination
212 of the process was accompanied by the creation of a core file
213 containing an image of the process when the signal was received.
214 .It Fn WSTOPSIG status
216 .Fn WIFSTOPPED status
217 is true, evaluates to the number of the signal
218 that caused the process to stop.
223 for a list of termination signals.
224 A status of 0 indicates normal termination.
226 If a parent process terminates without
227 waiting for all of its child processes to terminate,
228 the remaining child processes are assigned the parent
229 process 1 ID (the init process ID).
231 If a signal is caught while any of the
234 the call may be interrupted or restarted when the signal-catching routine
236 depending on the options in effect for the signal;
242 The implementation queues one
244 signal for each child process whose
245 status has changed, if
247 returns because the status of a child process is available, the pending
248 SIGCHLD signal associated with the process ID of the child process will
252 signals remain pending.
258 returns because the status of a child process is available, the pending
260 signal will be cleared unless another status of the child process
265 returns due to a stopped, continued,
266 or terminated child process, the process ID of the child
267 is returned to the calling process.
268 Otherwise, a value of \-1
271 is set to indicate the error.
278 returns due to a stopped, continued,
279 or terminated child process, the process ID of the child
280 is returned to the calling process.
281 If there are no children not previously awaited,
288 is specified and there are
289 no stopped, continued or exited children,
291 If an error is detected or a caught signal aborts the call,
295 is set to indicate the error.
300 will fail and return immediately if:
303 The calling process has no existing unwaited-for
306 No status from the terminated child process is available
307 because the calling process has asked the system to discard
308 such status by ignoring the signal
318 argument points to an illegal address.
319 (May not be detected before exit of a child process.)
321 The call was interrupted by a caught signal,
322 or the signal did not have the
337 functions are defined by POSIX;
341 are not specified by POSIX.
345 and the ability to restart a pending
347 call are extensions to the POSIX interface.