wait4(2) - f37

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

35       These functions are nonstandard; in new programs, the use of waitpid(2)
36       or waitid(2) is preferable.
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38       The wait3() and wait4() system calls are similar to waitpid(2), but ad‐
39       ditionally  return  resource  usage  information about the child in the
40       structure pointed to by rusage.
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42       Other than the use of the rusage argument, the following wait3() call:
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44           wait3(wstatus, options, rusage);
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46       is equivalent to:
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48           waitpid(-1, wstatus, options);
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50       Similarly, the following wait4() call:
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52           wait4(pid, wstatus, options, rusage);
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54       is equivalent to:
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56           waitpid(pid, wstatus, options);
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58       In other words, wait3() waits of any child, while wait4() can  be  used
59       to select a specific child, or children, on which to wait.  See wait(2)
60       for further details.
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62       If rusage is not NULL, the struct rusage to which  it  points  will  be
63       filled  with  accounting information about the child.  See getrusage(2)
64       for details.
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RETURN VALUE

67       As for waitpid(2).
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ERRORS

70       As for waitpid(2).
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CONFORMING TO

73       4.3BSD.
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75       SUSv1 included a specification of wait3(); SUSv2 included wait3(),  but
76       marked it LEGACY; SUSv3 removed it.
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NOTES

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

91       This page is part of release 5.13 of the Linux  man-pages  project.   A
92       description  of  the project, information about reporting bugs, and the
93       latest    version    of    this    page,    can     be     found     at
94       https://www.kernel.org/doc/man-pages/.
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98Linux                             2021-03-22                          WAIT4(2)