wait3.2 (2010 09)

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wait3(2) wait3(2)

APPLICATION USAGE

Threads Considerations

In a multi-threaded application, only the calling thread is suspended by

wait3()

and wait4().

The

wait3() and wait4() functions will not return until all threads in the process have reached the

desired state. For example, wait3() and

wait4() will not return until all threads have terminated.

If the

WUNTRACED or WCONTINUED options are speciﬁed,

wait3() and wait4() will not return until

all threads have stopped or continued respectively.

RETURN VALUE

wait3(), wait4(),orwaitpid()

returns because the status of a child process is available, the

return value is the process ID of that child process. If wait3(), wait4(),orwaitpid() returns due

to the receipt of a signal, the return value receives a

-1 and errno is set to [EINTR].

wait3() or wait4() was called with the

WNOHANG options argument where status is not available

for any process speciﬁed by the pid argument,

0 will be returned.

Otherwise, (pid_t)

-1 will be returned and

errno will be set to indicate the error.

ERRORS

wait3() or wait4() fails, errno is set to one of the following values:

[ECHILD] The calling process has no existing unwaited-for child processes; or the states

speciﬁed by the options argument are invalid for the set of processes speciﬁed by

the pid argument.

[EFAULT] Problems were encountered in the retrieval of status information for the speciﬁed

child process.

[EINTR] The wait3() or wait4() function has been interrupted by a signal. The value in

the location pointed to by the stat_loc argument is undeﬁned.

[EINVAL] The options argument to

wait3(), wait4(),or

waitpid() is invalid.

WARNINGS

The behavior of

wait3() and wait4() is affected if the SIGCLD signal is set to

SIG_IGN. See the

WARNINGS section of signal(5). Signal handlers that cause system calls to be restarted can affect the

[EINTR] condition described above (see bsdproc (3C) and sigaction (2)).

AUTHOR

The

wait3() and wait4() functions were developed by HP, AT&T, and the University of California,

Berkeley.