wait4(2) - Linux manual page (original) (raw)


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 feature_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 >= 500

   **wait4**():
       Since glibc 2.19:
           _DEFAULT_SOURCE
       glibc 2.19 and earlier:
           _BSD_SOURCE

DESCRIPTION top

   These functions are nonstandard; in new programs, the use of
   [waitpid(2)](../man2/waitpid.2.html) or [waitid(2)](../man2/waitid.2.html) is preferable.

   The **wait3**() and **wait4**() system calls are similar to [waitpid(2)](../man2/waitpid.2.html),
   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**()
   call:

       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)](../man2/wait.2.html) 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)](../man2/getrusage.2.html) for details.

RETURN VALUE top

   As for [waitpid(2)](../man2/waitpid.2.html).

ERRORS top

   As for [waitpid(2)](../man2/waitpid.2.html).

STANDARDS top

   None.

HISTORY top

   4.3BSD.

   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
   _<sys/time.h>_.)

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

SEE ALSO top

   [fork(2)](../man2/fork.2.html), [getrusage(2)](../man2/getrusage.2.html), [sigaction(2)](../man2/sigaction.2.html), [signal(2)](../man2/signal.2.html), [wait(2)](../man2/wait.2.html), [signal(7)](../man7/signal.7.html)

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Linux man-pages 6.10 2024-07-23 wait4(2)


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