waitid(2) System Calls waitid(2)
NAME
waitid - 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:
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 operation of any of the
following 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 ALSO
Intro(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 5.11 9 Jun 2004 waitid(2)