[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    waitid(2) manual page Table of Contents

Name

waitid - wait for child process to change state

Synopsis


#include <sys/types.h>
#include <wait.h>

int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);

Description

waitid() suspends the calling process until one of its children changes state. It records the current state of a child in the structure pointed to by infop. If a child process changed state prior to the call to waitid(), waitid() returns immediately.

The idtype and id arguments specify which children waitid() is to wait for.

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 an OR 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(2) ).

infop must point to a siginfo_t structure, as defined in siginfo(5) . siginfo_t is filled in by the system with the status of the process being waited for.

waitid(), with idtype equal to P_ALL and options equal to WEXITED|WTRAPPED, is equivalent to wait(2) .

Return Values

If waitid() returns due to a change of state of one of its children, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

Errors

waitid() fails if one or more of the following is true.

ECHILD
The set of processes specified by idtype and id does not contain any unwaited-for processes.
EFAULT
infop points to an illegal address.
EINTR
waitid() was interrupted due to the receipt of a signal by the calling process.
EINVAL
An invalid value was specified for options.
EINVAL
idtype and id specify an invalid set of processes.

See Also

intro(2) , exec(2) , exit(2) , fork(2) , pause(2) , ptrace(2) , sigaction(2) , wait(2) , signal(3C) , siginfo(5)

Table of Contents