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wait4(2) — Linux manual page

wait4(2)                   System Calls Manualwait4(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 *_Nullablewstatus, intoptions,struct rusage *_Nullablerusage);pid_t wait4(pid_tpid, int *_Nullablewstatus, intoptions,struct rusage *_Nullablerusage);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):wait3():           Since glibc 2.26:               _DEFAULT_SOURCE                   || (_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 >= 500wait4():           Since glibc 2.19:               _DEFAULT_SOURCE           glibc 2.19 and earlier:               _BSD_SOURCE

DESCRIPTION        top

       These functions are nonstandard; in new programs, the use ofwaitpid(2) orwaitid(2) is preferable.       Thewait3() andwait4() system calls are similar towaitpid(2),       but additionally return resource usage information about the child       in the structure pointed to byrusage.       Other than the use of therusage argument, the followingwait3()       call:           wait3(wstatus, options, rusage);       is equivalent to:           waitpid(-1, wstatus, options);       Similarly, the followingwait4() call:           wait4(pid, wstatus, options, rusage);       is equivalent to:           waitpid(pid, wstatus, options);       In other words,wait3() waits of any child, whilewait4() can be       used to select a specific child, or children, on which to wait.       Seewait(2) for further details.       Ifrusage is not NULL, thestruct rusage to which it points will       be filled with accounting information about the child.  Seegetrusage(2) for details.

RETURN VALUE        top

       As forwaitpid(2).

ERRORS        top

       As forwaitpid(2).

STANDARDS        top

       None.

HISTORY        top

       4.3BSD.       SUSv1 included a specification ofwait3(); SUSv2 includedwait3(),       but marked it LEGACY; SUSv3 removed it.       Including<sys/time.h> is not required these days, but increases       portability.  (Indeed,<sys/resource.h> defines therusage       structure with fields of typestruct timeval defined in<sys/time.h>.)C library/kernel differences       On Linux,wait3() is a library function implemented on top of thewait4() system call.

SEE ALSO        top

fork(2),getrusage(2),sigaction(2),signal(2),wait(2),signal(7)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17wait4(2)

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

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