waitid - wait for child process to change state
int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);
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.
The idtype and id arguments are used to specify which children
waitid() will wait for.
If idtype is P_PID, waitid() will wait for the child with a process ID
equal to (pid_t)pid.
If idtypeis P_PGID, waitid() will wait for any child with a process
group ID equal to (pid_t)pid.
If idtypeis P_ALL, waitid() will wait for any children and id is
The options argument is used to specify which state changes waitid()
will wait for. It is formed by OR-ing together one or more of the
WEXITED Wait for processes that have exited.
WSTOPPED Status will be returned for any child
that has stopped upon receipt of a
WCONTINUED Status will be returned for any child
that was stopped and has been continued.
WNOHANG Return immediately if there are no
children to wait for.
WNOWAIT Keep the process whose status is
returned in infop in a waitable state.
This will not affect the state of the
process; the process may be waited for
again after this call completes.
The infop argument must point to a siginfo_t structure. If waitid()
returns because a child process was found that satisfied the
conditions indicated by the arguments idtype and options, then the
Hewlett-Packard Company - 1 - HP-UX Release 11i: November 2000
structure pointed to by infop will be filled in by the system with the
status of the process. The si_signo member will always be equal to
If waitid() returns due to the change of state of one of its children,
0 is returned. Otherwise, -1 is returned and errno is set to indicate
The waitid() function will fail if:
[ECHILD] The calling process has no existing unwaited-for
[EINTR] The waitid() function was interrupted due to the
receipt of a signal by the calling process.
[EINVAL] An invalid value was specified for options, or
idtype and id specify an invalid set of processes.
In a multi-threaded application, only the calling thread is suspended
waitid() will not return until all threads in the process have reached
the desired state. For example, if the WEXITED, WSTOPPED or
WCONTINUED options are specified, waitid() will not return until all
threads in the process have terminated, stopped or continued
exec(2), exit(2), wait(2), <sys/wait.h>.
First released in Issue 4, Version 2.
Hewlett-Packard Company - 2 - HP-UX Release 11i: November 2000