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waitid.2 (2010 09)

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waitid(2) waitid(2)
NAME
waitid - wait for child process to change state
SYNOPSIS
#include <sys/wait.h>
int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);
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.
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 idtype is
P_PGID, waitid() will wait for any child with a process group ID equal to (pid_t)pid .
If idtype is
P_ALL, waitid() will wait for any children and id is ignored.
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 following flags:
WEXITED Wait for processes that have exited.
WSTOPPED Status will be returned for any child that has stopped upon receipt of a
signal.
WCONTINUED Status will be returned for any child that was stopped and has been con-
tinued.
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 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
SIGCHLD.
RETURN VALUE
If
waitid() returns due to the change of state of one of its children, 0 is returned. Otherwise, −1is
returned and
errno is set to indicate the error.
ERRORS
The
waitid() function will fail if:
[ECHILD] The calling process has no existing unwaited-for child processes.
[EINTR] The
waitid() function was interrupted due to the receipt of a signal by the cal-
ling process.
[EINVAL] An invalid value was specified for options ,oridtype and id specify an invalid set of
processes.
APPLICATION USAGE
Threads Considerations
In a multi-threaded application, only the calling thread is suspended by waitid().
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 respectively.
SEE ALSO
exec(2), exit(2), wait(2), <sys/wait.h>.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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