waitid(2) System Calls waitid(2)NAMEwaitid - wait for child process to change state
SYNOPSIS
#include <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
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:
· 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 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 operation of any of the follow‐
ing flags:
WCONTINUED Return the status for any child that was stopped and
has been continued.
WEXITED Wait for process(es) to exit.
WNOHANG Return immediately.
WNOWAIT Keep the process in a waitable state.
WSTOPPED Wait for and return the process status of any child
that has stopped upon receipt of a signal.
WTRAPPED Wait for traced process(es) to become trapped or reach
a breakpoint (see ptrace(3C)).
The infop argument must point to a siginfo_t structure, as defined in
siginfo.h(3HEAD). If waitid() returns because a child process was found
that satisfies the conditions indicated by the arguments idtype and
options, then the structure 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.
One instance of a SIGCHLD signal is queued for each child process whose
status has changed. If waitid() returns because the status of a child
process is available and WNOWAIT was not specified in options, any
pending SIGCHLD signal associated with the process ID of that child
process is discarded. Any other pending SIGCHLD signals remain pending.
RETURN VALUES
If waitid() returns due to a change of state of one of its children and
WNOHANG was not used, 0 is returned. Otherwise, −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.
ERRORS
The waitid() function will fail if:
ECHILD The set of processes specified by idtype and id does
not contain any unwaited processes.
EFAULT 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.
EINVAL An invalid value was specified for options, or idtype
and id specify an invalid set of processes.
USAGE
With options equal to WEXITED | WTRAPPED, waitid() is equivalent to
waitpid(3C). With idtype equal to P_ALL and options equal to WEXITED |
WTRAPPED, waitid() is equivalent to wait(3C).
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Async-Signal-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOintro(2), exec(2), exit(2), fork(2), pause(2), sigaction(2),
ptrace(3C), signal(3C), siginfo.h(3HEAD), wait(3C), waitpid(3C),
attributes(5), standards(5)SunOS 5.10 9 Jun 2004 waitid(2)
