wait4(2) - f34

1WAIT4(2)                   Linux Programmer's Manual                  WAIT4(2)
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NAME

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

9       #include <sys/types.h>
10       #include <sys/time.h>
11       #include <sys/resource.h>
12       #include <sys/wait.h>
13
14       pid_t wait3(int *wstatus, int options,
15                   struct rusage *rusage);
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17       pid_t wait4(pid_t pid, int *wstatus, int options,
18                   struct rusage *rusage);
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20   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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22       wait3():
23           Since glibc 2.26:
24               _DEFAULT_SOURCE ||
25               (_XOPEN_SOURCE >= 500 &&
26                       ! (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600))
27           From glibc 2.19 to 2.25:
28               _DEFAULT_SOURCE || _XOPEN_SOURCE >= 500
29           Glibc 2.19 and earlier:
30               _BSD_SOURCE || _XOPEN_SOURCE >= 500
31       wait4():
32           Since glibc 2.19:
33               _DEFAULT_SOURCE
34           Glibc 2.19 and earlier:
35               _BSD_SOURCE
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DESCRIPTION

38       These functions are nonstandard; in new programs, the use of waitpid(2)
39       or waitid(2) is preferable.
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41       The wait3() and wait4() system calls are similar to waitpid(2), but ad‐
42       ditionally  return  resource  usage  information about the child in the
43       structure pointed to by rusage.
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45       Other than the use of the rusage argument, the following wait3() call:
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47           wait3(wstatus, options, rusage);
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49       is equivalent to:
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51           waitpid(-1, wstatus, options);
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53       Similarly, the following wait4() call:
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55           wait4(pid, wstatus, options, rusage);
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57       is equivalent to:
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59           waitpid(pid, wstatus, options);
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61       In other words, wait3() waits of any child, while wait4() can  be  used
62       to select a specific child, or children, on which to wait.  See wait(2)
63       for further details.
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65       If rusage is not NULL, the struct rusage to which  it  points  will  be
66       filled  with  accounting information about the child.  See getrusage(2)
67       for details.
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RETURN VALUE

70       As for waitpid(2).
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ERRORS

73       As for waitpid(2).
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CONFORMING TO

76       4.3BSD.
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78       SUSv1 included a specification of wait3(); SUSv2 included wait3(),  but
79       marked it LEGACY; SUSv3 removed it.
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NOTES

82       Including <sys/time.h> is not required these days, but increases porta‐
83       bility.  (Indeed, <sys/resource.h> defines the  rusage  structure  with
84       fields of type struct timeval defined in <sys/time.h>.)
85
86   C library/kernel differences
87       On  Linux,  wait3()  is  a  library  function implemented on top of the
88       wait4() system call.
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COLOPHON

94       This page is part of release 5.10 of the Linux  man-pages  project.   A
95       description  of  the project, information about reporting bugs, and the
96       latest    version    of    this    page,    can     be     found     at
97       https://www.kernel.org/doc/man-pages/.
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101Linux                             2020-06-09                          WAIT4(2)