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waitid(2)
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 obtains status information pertaining to termina‐
tion, stop, and/or continue events in one of the caller's child
processes. The calling thread blocks until an error occurs, or status
information becomes available to the calling thread. This occurs when
information is available for one of the child processes specified by
the idtype and id arguments, and the state change matches one of the
state change flags set in the options argument.
waitid() 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 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 op‐
tions, 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 er‐
rno is set to indicate the error. If WNOHANG was used, 0 can be re‐
turned (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 con‐
tain 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(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelAsync-Signal-
Safe _ StandardSee standards(7).
SEE ALSO
exec(2), exit(2), fork(2), Intro(2), pause(2), sigaction(2),
ptrace(3C), signal(3C), wait(3C), waitpid(3C), siginfo.h(3HEAD), at‐
tributes(7), standards(7)
HISTORY
The waitid() function has been included in Solaris since Solaris 2.0.
Oracle Solaris 11.4 30 Jan 2023 waitid(2)