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>
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  26 .\" Modified Sat Jul 24 13:32:44 1993 by Rik Faith (faith@cs.unc.edu)
  27 .\" Modified Mon Jun 23 14:09:52 1997 by aeb - add EINTR.
  28 .\" Modified Tue Jul  7 12:26:42 1998 by aeb - changed return value wait3
  29 .\" Modified 2004-11-11, Michael Kerrisk <mtk.manpages@gmail.com>
  30 .\"     Rewrote much of this page, and removed much duplicated text,
  31 .\"             replacing with pointers to wait.2
  32 .\"
  33 .TH WAIT4 2  2018-04-30 "Linux" "Linux Programmer's Manual"
  34 .SH NAME
  35 wait3, wait4 \- wait for process to change state, BSD style
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <sys/types.h>
  39 .B #include <sys/time.h>
  40 .B #include <sys/resource.h>
  41 .B #include <sys/wait.h>
  42 .PP
  43 .BI "pid_t wait3(int *" "wstatus" ", int " options ,
  44 .BI "            struct rusage *" rusage );
  45 .PP
  46 .BI "pid_t wait4(pid_t " pid ", int *" wstatus ", int " options ,
  47 .BI "            struct rusage *" rusage );
  48 .fi
  49 .PP
  50 .in -4n
  51 Feature Test Macro Requirements for glibc (see
  52 .BR feature_test_macros (7)):
  53 .in
  54 .PP
  55 .ad l
  56 .BR wait3 ():
  57     Since glibc 2.26:
  58         _DEFAULT_SOURCE ||
  59         (_XOPEN_SOURCE\ >=\ 500 &&
  60                 ! (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600))
  61     From glibc 2.19 to 2.25:
  62         _DEFAULT_SOURCE || _XOPEN_SOURCE\ >=\ 500
  63     Glibc 2.19 and earlier:
  64         _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
  65 .\"          || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  66 .br
  67 .BR wait4 ():
  68     Since glibc 2.19:
  69         _DEFAULT_SOURCE
  70     Glibc 2.19 and earlier:
  71         _BSD_SOURCE
  72 .ad
  73 .SH DESCRIPTION
  74 These functions are nonstandard; in new programs, the use of
  75 .BR waitpid (2)
  76 or
  77 .BR waitid (2)
  78 is preferable.
  79 .PP
  80 The
  81 .BR wait3 ()
  82 and
  83 .BR wait4 ()
  84 system calls are similar to
  85 .BR waitpid (2),
  86 but additionally return resource usage information about the
  87 child in the structure pointed to by
  88 .IR rusage .
  89 .PP
  90 Other than the use of the
  91 .I rusage
  92 argument, the following
  93 .BR wait3 ()
  94 call:
  95 .PP
  96 .in +4n
  97 .EX
  98 wait3(wstatus, options, rusage);
  99 .EE
 100 .in
 101 .PP
 102 is equivalent to:
 103 .PP
 104 .in +4n
 105 .EX
 106 waitpid(\-1, wstatus, options);
 107 .EE
 108 .in
 109 .PP
 110 Similarly, the following
 111 .BR wait4 ()
 112 call:
 113 .PP
 114 .in +4n
 115 .EX
 116 wait4(pid, wstatus, options, rusage);
 117 .EE
 118 .in
 119 .PP
 120 is equivalent to:
 121 .PP
 122 .in +4n
 123 .EX
 124 waitpid(pid, wstatus, options);
 125 .EE
 126 .in
 127 .PP
 128 In other words,
 129 .BR wait3 ()
 130 waits of any child, while
 131 .BR wait4 ()
 132 can be used to select a specific child, or children, on which to wait.
 133 See
 134 .BR wait (2)
 135 for further details.
 136 .PP
 137 If
 138 .I rusage
 139 is not NULL, the
 140 .I struct rusage
 141 to which it points will be filled with accounting information
 142 about the child.
 143 See
 144 .BR getrusage (2)
 145 for details.
 146 .SH RETURN VALUE
 147 As for
 148 .BR waitpid (2).
 149 .SH ERRORS
 150 As for
 151 .BR waitpid (2).
 152 .SH CONFORMING TO
 153 4.3BSD.
 154 .PP
 155 SUSv1 included a specification of
 156 .BR wait3 ();
 157 SUSv2 included
 158 .BR wait3 (),
 159 but marked it LEGACY;
 160 SUSv3 removed it.
 161 .SH NOTES
 162 Including
 163 .I <sys/time.h>
 164 is not required these days, but increases portability.
 165 (Indeed,
 166 .I <sys/resource.h>
 167 defines the
 168 .I rusage
 169 structure with fields of type
 170 .I struct timeval
 171 defined in
 172 .IR <sys/time.h> .)
 173 .SS C library/kernel differences
 174 On Linux,
 175 .BR wait3 ()
 176 is a library function implemented on top of the
 177 .BR wait4 ()
 178 system call.
 179 .SH SEE ALSO
 180 .BR fork (2),
 181 .BR getrusage (2),
 182 .BR sigaction (2),
 183 .BR signal (2),
 184 .BR wait (2),
 185 .BR signal (7)