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32 .\" @(#)wait.2 8.2 (Berkeley) 4/19/94
43 .Nd wait for process termination
50 .Fn wait "int *status"
54 .Fn waitpid "pid_t wpid" "int *status" "int options"
56 .Fn wait3 "int *status" "int options" "struct rusage *rusage"
58 .Fn wait4 "pid_t wpid" "int *status" "int options" "struct rusage *rusage"
62 function suspends execution of its calling process until
64 information is available for a terminated child process,
65 or a signal is received.
66 On return from a successful
71 area contains termination information about the process that exited
76 system call provides a more general interface for programs
77 that need to wait for certain child processes,
78 that need resource utilization statistics accumulated by child processes,
79 or that require options.
80 The other wait functions are implemented using
85 argument specifies the set of child processes for which to wait.
88 is -1, the call waits for any child process.
92 the call waits for any child process in the process group of the caller.
95 is greater than zero, the call waits for the process with process id
99 is less than -1, the call waits for any process whose process group id
100 equals the absolute value of
105 argument is defined below.
108 argument contains the bitwise OR of any of the following options.
111 option indicates that children of the current process that
112 have continued from a job control stop, by receiving a
114 signal, should also have their status reported.
118 is used to indicate that the call should not block if
119 there are no processes that wish to report status.
123 children of the current process that are stopped
125 .Dv SIGTTIN , SIGTTOU , SIGTSTP ,
129 their status reported.
133 is non-zero, a summary of the resources used by the terminated
135 children is returned (this information is currently not available
136 for stopped processes).
140 option is specified and no processes
141 wish to report status,
149 function is identical to
162 The following macros may be used to test the manner of exit of the process.
163 One of the first three macros will evaluate to a non-zero (true) value:
165 .It Fn WIFCONTINUED status
166 True if the process has not terminated, and
167 has continued after a job control stop.
168 This macro can be true only if the wait call specified the
171 .It Fn WIFEXITED status
172 True if the process terminated normally by a call to
176 .It Fn WIFSIGNALED status
177 True if the process terminated due to receipt of a signal.
178 .It Fn WIFSTOPPED status
179 True if the process has not terminated, but has stopped and can be restarted.
180 This macro can be true only if the wait call specified the
183 or if the child process is being traced (see
187 Depending on the values of those macros, the following macros
188 produce the remaining status information about the child process:
190 .It Fn WEXITSTATUS status
193 is true, evaluates to the low-order 8 bits
194 of the argument passed to
199 .It Fn WTERMSIG status
201 .Fn WIFSIGNALED status
202 is true, evaluates to the number of the signal
203 that caused the termination of the process.
204 .It Fn WCOREDUMP status
206 .Fn WIFSIGNALED status
207 is true, evaluates as true if the termination
208 of the process was accompanied by the creation of a core file
209 containing an image of the process when the signal was received.
210 .It Fn WSTOPSIG status
212 .Fn WIFSTOPPED status
213 is true, evaluates to the number of the signal
214 that caused the process to stop.
219 for a list of termination signals.
220 A status of 0 indicates normal termination.
222 If a parent process terminates without
223 waiting for all of its child processes to terminate,
224 the remaining child processes are assigned the parent
225 process 1 ID (the init process ID).
227 If a signal is caught while any of the
230 the call may be interrupted or restarted when the signal-catching routine
232 depending on the options in effect for the signal;
239 returns due to a stopped
240 or terminated child process, the process ID of the child
241 is returned to the calling process.
242 Otherwise, a value of -1
245 is set to indicate the error.
252 returns due to a stopped
253 or terminated child process, the process ID of the child
254 is returned to the calling process.
255 If there are no children not previously awaited,
262 is specified and there are
263 no stopped or exited children,
265 If an error is detected or a caught signal aborts the call,
269 is set to indicate the error.
274 will fail and return immediately if:
277 The calling process has no existing unwaited-for
280 No status from the terminated child process is available
281 because the calling process has asked the system to discard
282 such status by ignoring the signal
292 argument points to an illegal address.
293 (May not be detected before exit of a child process.)
295 The call was interrupted by a caught signal,
296 or the signal did not have the
310 functions are defined by POSIX;
314 are not specified by POSIX.
318 and the ability to restart a pending
320 call are extensions to the POSIX interface.