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Caution: This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.

waitid()

Wait for a child process to change state

Synopsis:

#include <sys/wait.h>

int waitid( idtype_t idtype,
            id_t id,
            siginfo_t * infop,
            int options );

Arguments:

idtype
Which children you want to wait for:
id
The process or process group ID that you want to wait for, depending on the value of idtype.
infop
A pointer to a siginfo_t structure, as defined in <sys/siginfo.h>, where the function can store the current state of the child; see below.
options
A combination of zero or more of the following flags:

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The waitid() function suspends the calling process until one of its children changes state. It records the current state of a child in the structure pointed to by infop. If a child process changed state prior to the call to waitid(), waitid() returns immediately.

If waitid() returns because a child process was found that satisfied the conditions indicated by the arguments idtype and options, then the structure pointed to by infop is filled in by the system with the status of the process. The si_signo member is always SIGCHLD.

If idtype is P_ALL and options is WEXITED|WTRAPPED, waitid() is equivalent to wait().

Returns:

0
One of the children changed its state. If WNOHANG was used, 0 can be returned (indicating no error); however, no children may have changed state if info->si_pid is 0.
-1
An error occurred (errno is set).

Errors:

ECHILD
The set of processes specified by idtype and id doesn't contain any unwaited-for processes.
EFAULT
The infop argument points to an illegal address.
EINTR
The waitid() function was interrupted by a signal.
EINVAL
An invalid value was specified for options, or idtype and id specify an invalid set of processes.

Classification:

POSIX 1003.1 XSI

Safety:
Cancellation point Yes
Interrupt handler No
Signal handler Yes
Thread Yes

See also:

execl(), execle(), execlp(), execlpe(), execv(), execve(), execvp(), execvpe(), exit(), fork(), pause(), sigaction(), signal(), wait(), wait3(), wait4(), waitpid()


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