man2/sigwaitinfo.2

   1 .\" Copyright (c) 2002 Michael kerrisk <mtk-manpages@gmx.net>
   2 .\"
   3 .\" Permission is granted to make and distribute verbatim copies of this
   4 .\" manual provided the copyright notice and this permission notice are
   5 .\" preserved on all copies.
   6 .\"
   7 .\" Permission is granted to copy and distribute modified versions of this
   8 .\" manual under the conditions for verbatim copying, provided that the
   9 .\" entire resulting derived work is distributed under the terms of a
  10 .\" permission notice identical to this one.
  11 .\"
  12 .\" Since the Linux kernel and libraries are constantly changing, this
  13 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
  14 .\" responsibility for errors or omissions, or for damages resulting from
  15 .\" the use of the information contained herein.
  16 .\"
  17 .\" Formatted or processed versions of this manual, if unaccompanied by
  18 .\" the source, must acknowledge the copyright and authors of this work.
  19 .\"
  20 .TH SIGWAITINFO 2 2002-06-07 "Linux 2.4.18" "Linux Programmer's Manual"
  21 .SH NAME
  22 sigwaitinfo, sigtimedwait \- synchronously wait for queued signals
  23 .SH SYNOPSIS
  24 .B #include <signal.h>
  25 .sp
  26 .BI "int sigwaitinfo(const sigset_t *" set ", siginfo_t *" info ");"
  27 .sp
  28 .BI "int sigtimedwait(const sigset_t *" set ", siginfo_t *" info ", "
  29 .BI "const struct timespec *" timeout ");"
  30 .SH DESCRIPTION
  31 .BR sigwaitinfo ()
  32 suspends execution of the calling process until one of the signals in
  33 .I set
  34 is delivered.
  35 (If one of the signals in
  36 .I set
  37 is already pending for the calling process,
  38 .BR sigwaitinfo ()
  39 will return immediately with information about that signal.)
  40
  41 .BR sigwaitinfo ()
  42 removes the delivered signal from the calling process's list of pending
  43 signals and returns the signal number as its function result.
  44 If the
  45 .I info
  46 argument is not
  47 .BR NULL ,
  48 then it returns a structure of type
  49 .I siginfo_t
  50 (see
  51 .BR sigaction (2))
  52 containing information about the signal.
  53 .PP
  54 Signals returned via
  55 .BR sigwaitinfo ()
  56 are delivered in the usual order; see
  57 .BR signal (7)
  58 for further details.
  59 .PP
  60 .BR sigtimedwait ()
  61 operates in exactly the same way as
  62 .BR sigwaitinfo ()
  63 except that it has an additional argument,
  64 .IR timeout ,
  65 which enables an upper bound to be placed on the time for which
  66 the process is suspended.
  67 This argument is of the following type:
  68 .sp
  69 .in +2n
  70 .nf
  71 struct timespec {
  72     long    tv_sec;         /* seconds */
  73     long    tv_nsec;        /* nanoseconds */
  74 }
  75 .fi
  76 .in -2n
  77 .sp
  78 If both fields of this structure are specified as 0, a poll is performed:
  79 .BR sigtimedwait ()
  80 returns immediately, either with information about a signal that
  81 was pending for the caller, or with an error
  82 if none of the signals in
  83 .I set
  84 was pending.
  85 .SH "RETURN VALUE"
  86 On success, both
  87 .BR sigwaitinfo ()
  88 and
  89 .BR sigtimedwait ()
  90 return a signal number (i.e., a value greater than zero).
  91 On failure both calls return \-1, with
  92 .I errno
  93 set to indicate the error.
  94 .SH ERRORS
  95 .TP
  96 .B EAGAIN
  97 No signal in
  98 .I set
  99 was delivered within the
 100 .I timeout
 101 period specified to
 102 .BR sigtimedwait ().
 103 .TP
 104 .B EINTR
 105 The wait was interrupted by a signal handler.
 106 (This handler was for a signal other than one of those in
 107 .IR set .)
 108 .TP
 109 .B EINVAL
 110 .I timeout
 111 was invalid.
 112 .SH NOTES
 113 In normal usage, the caller blocks the signals in
 114 .I set
 115 via a prior call to
 116 .BR sigprocmask ()
 117 (so that the default disposition for these signals does not occur if they
 118 are delivered between successive calls to
 119 .BR sigwaitinfo () or
 120 .BR sigtimedwait())
 121 and does not establish handlers for these signals.
 122 .PP
 123 POSIX leaves the meaning of a
 124 .B NULL
 125 value for the
 126 .I timeout
 127 argument of
 128 .BR sigtimedwait ()
 129 unspecified, permitting the possibility that this has the same meaning
 130 as a call to
 131 .BR sigwaitinfo (),
 132 and indeed this is what is done on Linux.
 133 .SH "CONFORMING TO"
 134 POSIX 1003.1-2001
 135 .SH "SEE ALSO"
 136 .BR kill (2),
 137 .BR sigaction (2),
 138 .BR signal (2),
 139 .BR sigpending (2),
 140 .BR sigprocmask (2),
 141 .BR sigqueue (2),
 142 .BR sigsetops (3),
 143 .BR signal (7)