waitid - wait for child process to change state
int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int
The waitid() function suspends the calling process until one
of its child processes changes state. It records the current
state of a child in the structure pointed to by infop. It
returns immediately if a child process changed state prior
to the call.
The idtype and id arguments specify which children
waitid() is to wait for, as follows:
o If idtype is P_PID, waitid() waits for the child with
a process ID equal to (pid_t)id.
o If idtype is P_PGID, waitid() waits for any child
with a process group ID equal to (pid_t)id.
o If idtype is P_ALL, waitid() waits for any child and
id is ignored.
The options argument is used to specify which state changes
waitid() is to wait for. It is formed by bitwise OR opera-
tion of any of the following flags:
Return the status for any child that was stopped and
has been continued.
Wait for process(es) to exit.
Keep the process in a waitable state.
Wait for and return the process status of any child
that has stopped upon receipt of a signal.
Wait for traced process(es) to become trapped or reach
a breakpoint (see ptrace(2)).
The infop argument must point to a siginfo_t structure, as
defined in siginfo(3HEAD). If waitid() returns because a
child process was found that satisfies the conditions indi-
cated by the arguments idtype and options, then the struc-
ture pointed to by infop will be filled by the system with
the status of the process.
The si_signo member will always be equal to SIGCHLD.
If waitid() returns due to a change of state of one of its
children and WNOHANG was not used, 0 is returned. Other-
wise, -1 is returned and errno is set to indicate the
error. If WNOHANG was used, 0 can be returned (indicating
no error); however, no children may have changed state if
info->si_pid is 0.
The waitid() function will fail if:
The set of processes specified by idtype and id does
not contain any unwaited processes.
The infop argument points to an illegal address.
EINTR The waitid() function was interrupted due to the
receipt of a signal by the calling process.
An invalid value was specified for options, or idtype
and id specify an invalid set of processes.
With idtype equal to P_ALL and options equal to WEXITED |
WTRAPPED, waitid() is equivalent to wait(2).
intro(2), exec(2), exit(2), fork(2), pause(2), ptrace(2),
sigaction(2), wait(2), signal(3C), siginfo(3HEAD)
Man(1) output converted with