WAITPID(2-SVR4)     RISC/os Reference Manual      WAITPID(2-SVR4)



NAME
     waitpid - wait for child process to change state

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

     pidt waitpid (pidt pid, int *statloc, int options);

DESCRIPTION
     waitpid suspends the calling process until one of its chil-
     dren changes state; if a child process changed state prior
     to the call to waitpid, return is immediate.  pid specifies
     a set of child processes for which status is requested.

          If pid is equal to (pid_t)-1, status is requested for
          any child process.

          If pid is greater than (pid_t)0, it specifies the pro-
          cess ID of the child process for which status is
          requested.

          If pid is equal to (pid_t)0 status is requested for any
          child process whose process group ID is equal to that
          of the calling process.

          If pid is less than (pid_t)-1, status is requested for
          any child process whose process group ID is equal to
          the absolute value of pid.

     If waitpid returns because the status of a child process is
     available, then that status may be evaluated with the macros
     defined by wstat(5) . If the calling process had specified a
     non-zero value of stat_loc, the status of the child process
     will be stored in the location pointed to by stat_loc.

     The options argument is constructed from the bitwise
     inclusive OR of zero or more of the following flags, defined
     in the header file <sys/wait.h>:

     WCONTINUED     the status of any continued child process
                    specified by pid, whose status has not been
                    reported since it continued, shall also be
                    reported to the calling process.

     WNOHANG        waitpid will not suspend execution of the
                    calling process if status is not immediately
                    available for one of the child processes
                    specified by pid.

     WNOWAIT        keep the process whose status is returned in
                    stat_loc in a waitable state. The process may



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WAITPID(2-SVR4)     RISC/os Reference Manual      WAITPID(2-SVR4)



                    be waited for again with identical results.

     WUNTRACED      the status of any child processes specified
                    by pid that are stopped, and whose status has
                    not yet been reported since they stopped,
                    shall also be reported to the calling pro-
                    cess.

     waitpid with options equal to WUNTRACED and pid equal to
     (pid_t)-1 is identical to a call to wait(2).

     waitpid will fail if one or more of the following is true:

     EINTR          waitpid was interrupted due to the receipt of
                    a signal sent by the calling process.

     EINVAL         An invalid value was specified for options.

     ECHILD         The process or process group specified by pid
                    does not exist or is not a child of the cal-
                    ling process or can never be in the states
                    specified by options.

SEE ALSO
     exec(2), exit(2), fork(2), intro(2), pause(2), ptrace(2),
     signal(2), sigaction(2), siginfo(5), wstat(5)

DIAGNOSTICS
     If waitpid returns because the status of a child process is
     available, this function shall return a value equal to the
     process ID of the child process for which status is
     reported.  If waitpid returns due to the delivery of a sig-
     nal to the calling process, a value of -1 shall be returned
     and errno shall be set to EINTR. If this function was
     invoked with WNOHANG set in options, it has at least one
     child process specified by pid for which status is not
     available, and status is not available for any process
     specified by pid, a value of 0 shall be returned. Otherwise,
     a value of -1 shall be returned, and errno shall be set to
     indicate the error.















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