man2/wait4.2

   1 .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
   2 .\" and Copyright (c) 2004 by Michael Kerrisk <mtk.manpages@gmail.com>
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .\" Modified Sat Jul 24 13:32:44 1993 by Rik Faith (faith@cs.unc.edu)
   7 .\" Modified Mon Jun 23 14:09:52 1997 by aeb - add EINTR.
   8 .\" Modified Tue Jul  7 12:26:42 1998 by aeb - changed return value wait3
   9 .\" Modified 2004-11-11, Michael Kerrisk <mtk.manpages@gmail.com>
  10 .\"     Rewrote much of this page, and removed much duplicated text,
  11 .\"             replacing with pointers to wait.2
  12 .\"
  13 .TH wait4 2 (date) "Linux man-pages (unreleased)"
  14 .SH NAME
  15 wait3, wait4 \- wait for process to change state, BSD style
  16 .SH LIBRARY
  17 Standard C library
  18 .RI ( libc ", " \-lc )
  19 .SH SYNOPSIS
  20 .nf
  21 .B #include <sys/wait.h>
  22 .PP
  23 .BI "pid_t wait3(int *" "wstatus" ", int " options ", struct rusage *" rusage );
  24 .BI "pid_t wait4(pid_t " pid ", int *" wstatus ", int " options ,
  25 .BI "            struct rusage *" rusage );
  26 .fi
  27 .PP
  28 .RS -4
  29 Feature Test Macro Requirements for glibc (see
  30 .BR feature_test_macros (7)):
  31 .RE
  32 .PP
  33 .BR wait3 ():
  34 .nf
  35     Since glibc 2.26:
  36         _DEFAULT_SOURCE
  37             || (_XOPEN_SOURCE >= 500 &&
  38                 ! (_POSIX_C_SOURCE >= 200112L
  39                    || _XOPEN_SOURCE >= 600))
  40     From glibc 2.19 to 2.25:
  41         _DEFAULT_SOURCE || _XOPEN_SOURCE >= 500
  42     Glibc 2.19 and earlier:
  43         _BSD_SOURCE || _XOPEN_SOURCE >= 500
  44 .\"          || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  45 .fi
  46 .PP
  47 .BR wait4 ():
  48 .nf
  49     Since glibc 2.19:
  50         _DEFAULT_SOURCE
  51     Glibc 2.19 and earlier:
  52         _BSD_SOURCE
  53 .fi
  54 .SH DESCRIPTION
  55 These functions are nonstandard; in new programs, the use of
  56 .BR waitpid (2)
  57 or
  58 .BR waitid (2)
  59 is preferable.
  60 .PP
  61 The
  62 .BR wait3 ()
  63 and
  64 .BR wait4 ()
  65 system calls are similar to
  66 .BR waitpid (2),
  67 but additionally return resource usage information about the
  68 child in the structure pointed to by
  69 .IR rusage .
  70 .PP
  71 Other than the use of the
  72 .I rusage
  73 argument, the following
  74 .BR wait3 ()
  75 call:
  76 .PP
  77 .in +4n
  78 .EX
  79 wait3(wstatus, options, rusage);
  80 .EE
  81 .in
  82 .PP
  83 is equivalent to:
  84 .PP
  85 .in +4n
  86 .EX
  87 waitpid(\-1, wstatus, options);
  88 .EE
  89 .in
  90 .PP
  91 Similarly, the following
  92 .BR wait4 ()
  93 call:
  94 .PP
  95 .in +4n
  96 .EX
  97 wait4(pid, wstatus, options, rusage);
  98 .EE
  99 .in
 100 .PP
 101 is equivalent to:
 102 .PP
 103 .in +4n
 104 .EX
 105 waitpid(pid, wstatus, options);
 106 .EE
 107 .in
 108 .PP
 109 In other words,
 110 .BR wait3 ()
 111 waits of any child, while
 112 .BR wait4 ()
 113 can be used to select a specific child, or children, on which to wait.
 114 See
 115 .BR wait (2)
 116 for further details.
 117 .PP
 118 If
 119 .I rusage
 120 is not NULL, the
 121 .I struct rusage
 122 to which it points will be filled with accounting information
 123 about the child.
 124 See
 125 .BR getrusage (2)
 126 for details.
 127 .SH RETURN VALUE
 128 As for
 129 .BR waitpid (2).
 130 .SH ERRORS
 131 As for
 132 .BR waitpid (2).
 133 .SH STANDARDS
 134 4.3BSD.
 135 .PP
 136 SUSv1 included a specification of
 137 .BR wait3 ();
 138 SUSv2 included
 139 .BR wait3 (),
 140 but marked it LEGACY;
 141 SUSv3 removed it.
 142 .SH NOTES
 143 Including
 144 .I <sys/time.h>
 145 is not required these days, but increases portability.
 146 (Indeed,
 147 .I <sys/resource.h>
 148 defines the
 149 .I rusage
 150 structure with fields of type
 151 .I struct timeval
 152 defined in
 153 .IR <sys/time.h> .)
 154 .SS C library/kernel differences
 155 On Linux,
 156 .BR wait3 ()
 157 is a library function implemented on top of the
 158 .BR wait4 ()
 159 system call.
 160 .SH SEE ALSO
 161 .BR fork (2),
 162 .BR getrusage (2),
 163 .BR sigaction (2),
 164 .BR signal (2),
 165 .BR wait (2),
 166 .BR signal (7)