waitid(2)                                                         waitid(2)

NAME
     waitid - wait for child process to change state

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

     int waitid(idtypet idtype, idt id, siginfot *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 struc-
     ture 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 PPID, waitid() waits for the child with a process ID
        equal to (pidt)id.

     -  If idtype is PPGID, waitid() waits for any child with a process
        group ID equal to (pidt)id.

     -  If idtype is PALL, waitid() waits for any children and id is
        ignored.

     The options argument is used to specify which state changes waitid()
     is to wait for. It is formed by a bitwise OR of any of the following
     flags:

     WEXITED     Wait for process(es) to exit.

     WTRAPPED    Wait for traced process(es) to become trapped or reach a
                 breakpoint [see ptrace(2)].

     WSTOPPED    Wait for and return the process status of any child that
                 has stopped upon receipt of a signal.

     WCONTINUED  Return the status for any child that was stopped and has
                 been continued.

     WNOHANG     Return immediately if there are no children to wait for.

     WNOWAIT     Keep the process whose status is returned in infop in a
                 waitable state. This will not affect the state of the pro-
                 cess; the process may be waited for again after this call
                 completes.

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



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waitid(2)                                                         waitid(2)

ERRORS
     The following error code descriptions are function-specific. You will
     find a general description in introprm2(2) or in errno(5).

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

     EFAULT    infop points to an invalid 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.

     ECHILD    The set of processes specified by idtype and id does not
               contain any unwaited-for processes.

RESULT
     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.

SEE ALSO
     exec(2), exit(2), fork(2), pause(2), ptrace(2), signal(2),
     sigaction(2), wait(2), siginfo(5), types(5), wait(5).




























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