System Calls waitid(2)
NAME
waitid - wait for child process to change state
SYNOPSIS
#include
int waitid(idtypet idtype, idt id, siginfot *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 PID, waitid() waits for the child
with a process ID equal to (pidt)id.
o If idtype is PGID, waitid() waits for any child
with a process group ID equal to (pidt)id.
o If idtype is PAL, 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:
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.
WSTOPED Wait for and return the process status of any
child that has stopped upon receipt of a sig-
nal.
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System Calls waitid(2)
WTRAPED Wait for traced process(es) to become trapped
or reach a breakpoint (see ptrace(3C)).
The infop argument must point to a siginfot structure, as
defined in siginfo.h(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 sisigno 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 pend-
ing.
RETURN VALUES
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->sipid is 0.
ERORS
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 WTRAPED, waitid() is
equivalent to waitpid(3C). With idtype equal to PAL and
options equal to WEXITED WTRAPED, waitid() is equivalent
SunOS 5.11 Last change: 9 Jun 2004 2
System Calls waitid(2)
to wait(3C).
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE 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 Last change: 9 Jun 2004 3
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