waitid - wait for child process to change state
int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);
waitid 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 specify which children waitid is to wait for.
If idtype is P_PID, waitid waits for the child with a process ID
equal to (pid_t) id.
If idtype is P_PGID, waitid waits for any child with a process group
ID equal to (pid_t)id.
If idtype is P_ALL, waitid waits for any children and id is ignored.
The options argument is used to specify which state changes waitid is to
wait for. It is formed by an OR of any of the following flags:
WEXITED Wait for process(es) to exit.
WTRAPPED Wait for traced process(es) to become trapped or reach a
breakpoint (see ptrace(2)).
WSTOPPED Wait for and return the process status of any child that
has stopped upon receipt of a signal.
WCONTINUED Return the status for any child that was stopped and has
WNOHANG Return immediately.
WNOWAIT Keep the process in a waitable state.
infop must point to a siginfo_t structure, as defined in siginfo(5).
siginfo_t is filled in by the system with the status of the process being
waitid fails if one or more of the following is true.
EFAULT infop points to an invalid address.
EINTR waitid was interrupted due to the receipt of a signal by
the calling process.
EINVAL An invalid value was specified for options.
EINVAL idtype and id specify an invalid set of processes.
ECHILD The set of processes specified by idtype and id does not
contain any unwaited-for processes.
If waitid returns due to a change of state of one of its children, a
value of 0 is returned. If WNOHANG was specified, 0 may also be returned
indicating no error. Otherwise, a value of -1 is returned and errno is
set to indicate the error.
exec(2), exit(2), fork(2), intro(2), pause(2), ptrace(2), sigaction(2),
signal(2), wait(2), siginfo(5)
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