wait4(2) — Linux manual page


wait4(2)                   System Calls Manual                  wait4(2)

NAME         top

       wait3, wait4 - wait for process to change state, BSD style

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <sys/wait.h>

       pid_t wait3(int *_Nullable wstatus, int options,
                   struct rusage *_Nullable rusage);
       pid_t wait4(pid_t pid, int *_Nullable wstatus, int options,
                   struct rusage *_Nullable rusage);

   Feature Test Macro Requirements for glibc (see

           Since glibc 2.26:
                   || (_XOPEN_SOURCE >= 500 &&
                       ! (_POSIX_C_SOURCE >= 200112L
                          || _XOPEN_SOURCE >= 600))
           From glibc 2.19 to glibc 2.25:
               _DEFAULT_SOURCE || _XOPEN_SOURCE >= 500
           glibc 2.19 and earlier:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500

           Since glibc 2.19:
           glibc 2.19 and earlier:

DESCRIPTION         top

       These functions are nonstandard; in new programs, the use of
       waitpid(2) or waitid(2) is preferable.

       The wait3() and wait4() system calls are similar to waitpid(2),
       but additionally return resource usage information about the
       child in the structure pointed to by rusage.

       Other than the use of the rusage argument, the following wait3()

           wait3(wstatus, options, rusage);

       is equivalent to:

           waitpid(-1, wstatus, options);

       Similarly, the following wait4() call:

           wait4(pid, wstatus, options, rusage);

       is equivalent to:

           waitpid(pid, wstatus, options);

       In other words, wait3() waits of any child, while wait4() can be
       used to select a specific child, or children, on which to wait.
       See wait(2) for further details.

       If rusage is not NULL, the struct rusage to which it points will
       be filled with accounting information about the child.  See
       getrusage(2) for details.

RETURN VALUE         top

       As for waitpid(2).

ERRORS         top

       As for waitpid(2).

STANDARDS         top


HISTORY         top


       SUSv1 included a specification of wait3(); SUSv2 included
       wait3(), but marked it LEGACY; SUSv3 removed it.

       Including <sys/time.h> is not required these days, but increases
       portability.  (Indeed, <sys/resource.h> defines the rusage
       structure with fields of type struct timeval defined in

   C library/kernel differences
       On Linux, wait3() is a library function implemented on top of the
       wait4() system call.

SEE ALSO         top

       fork(2), getrusage(2), sigaction(2), signal(2), wait(2),

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                       wait4(2)

Pages that refer to this page: time(1)_exit(2)getrusage(2)syscalls(2)wait(2)popen(3)signal(7)