wait4(2) - f39

1wait4(2)                      System Calls Manual                     wait4(2)
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NAME

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

9       Standard C library (libc, -lc)
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SYNOPSIS

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

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

71       As for waitpid(2).
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ERRORS

74       As for waitpid(2).
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STANDARDS

77       None.
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HISTORY

80       4.3BSD.
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82       SUSv1 included a specification of wait3(); SUSv2 included wait3(),  but
83       marked it LEGACY; SUSv3 removed it.
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85       Including <sys/time.h> is not required these days, but increases porta‐
86       bility.  (Indeed, <sys/resource.h> defines the  rusage  structure  with
87       fields of type struct timeval defined in <sys/time.h>.)
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89   C library/kernel differences
90       On  Linux,  wait3()  is  a  library  function implemented on top of the
91       wait4() system call.
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