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 2.19:
  58         _DEFAULT_SOURCE || _XOPEN_SOURCE\ >=\ 500
  59     Glibc 2.19 and earlier:
  60         _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
  61 .\"          || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  62 .br
  63 .BR wait4 ():
  64     Since glibc 2.19:
  65         _DEFAULT_SOURCE
  66     Glibc 2.19 and earlier:
  67         _BSD_SOURCE
  68 .ad
  69 .SH DESCRIPTION
  70 These functions are nonstandard; in new programs, the use of
  71 .BR waitpid (2)
  72 or
  73 .BR waitid (2)
  74 is preferable.
  75 .PP
  76 The
  77 .BR wait3 ()
  78 and
  79 .BR wait4 ()
  80 system calls are similar to
  81 .BR waitpid (2),
  82 but additionally return resource usage information about the
  83 child in the structure pointed to by
  84 .IR rusage .
  85 .PP
  86 Other than the use of the
  87 .I rusage
  88 argument, the following
  89 .BR wait3 ()
  90 call:
  91 .PP
  92 .in +4n
  93 .EX
  94 wait3(wstatus, options, rusage);
  95 .EE
  96 .in
  97 .PP
  98 is equivalent to:
  99 .PP
 100 .in +4n
 101 .EX
 102 waitpid(\-1, wstatus, options);
 103 .EE
 104 .in
 105 .PP
 106 Similarly, the following
 107 .BR wait4 ()
 108 call:
 109 .PP
 110 .in +4n
 111 .EX
 112 wait4(pid, wstatus, options, rusage);
 113 .EE
 114 .in
 115 .PP
 116 is equivalent to:
 117 .PP
 118 .in +4n
 119 .EX
 120 waitpid(pid, wstatus, options);
 121 .EE
 122 .in
 123 .PP
 124 In other words,
 125 .BR wait3 ()
 126 waits of any child, while
 127 .BR wait4 ()
 128 can be used to select a specific child, or children, on which to wait.
 129 See
 130 .BR wait (2)
 131 for further details.
 132 .PP
 133 If
 134 .I rusage
 135 is not NULL, the
 136 .I struct rusage
 137 to which it points will be filled with accounting information
 138 about the child.
 139 See
 140 .BR getrusage (2)
 141 for details.
 142 .SH RETURN VALUE
 143 As for
 144 .BR waitpid (2).
 145 .SH ERRORS
 146 As for
 147 .BR waitpid (2).
 148 .SH CONFORMING TO
 149 4.3BSD.
 150 .PP
 151 SUSv1 included a specification of
 152 .BR wait3 ();
 153 SUSv2 included
 154 .BR wait3 (),
 155 but marked it LEGACY;
 156 SUSv3 removed it.
 157 .SH NOTES
 158 Including
 159 .I <sys/time.h>
 160 is not required these days, but increases portability.
 161 (Indeed,
 162 .I <sys/resource.h>
 163 defines the
 164 .I rusage
 165 structure with fields of type
 166 .I struct timeval
 167 defined in
 168 .IR <sys/time.h> .)
 169 .SS C library/kernel differences
 170 On Linux,
 171 .BR wait3 ()
 172 is a library function implemented on top of the
 173 .BR wait4 ()
 174 system call.
 175 .SH SEE ALSO
 176 .BR fork (2),
 177 .BR getrusage (2),
 178 .BR sigaction (2),
 179 .BR signal (2),
 180 .BR wait (2),
 181 .BR signal (7)