man3/sleep.3

   1 .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" Modified Sat Jul 24 18:16:02 1993 by Rik Faith (faith@cs.unc.edu)
   6 .TH sleep 3 (date) "Linux man-pages (unreleased)"
   7 .SH NAME
   8 sleep \- sleep for a specified number of seconds
   9 .SH LIBRARY
  10 Standard C library
  11 .RI ( libc ", " \-lc )
  12 .SH SYNOPSIS
  13 .nf
  14 .B #include <unistd.h>
  15 .PP
  16 .BI "unsigned int sleep(unsigned int " "seconds" );
  17 .fi
  18 .SH DESCRIPTION
  19 .BR sleep ()
  20 causes the calling thread to sleep either until
  21 the number of real-time seconds specified in
  22 .I seconds
  23 have elapsed or until a signal arrives which is not ignored.
  24 .SH RETURN VALUE
  25 Zero if the requested time has elapsed,
  26 or the number of seconds left to sleep,
  27 if the call was interrupted by a signal handler.
  28 .SH ATTRIBUTES
  29 For an explanation of the terms used in this section, see
  30 .BR attributes (7).
  31 .ad l
  32 .nh
  33 .TS
  34 allbox;
  35 lbx lb lb
  36 l l l.
  37 Interface       Attribute       Value
  38 T{
  39 .BR sleep ()
  40 T}      Thread safety   MT-Unsafe sig:SIGCHLD/linux
  41 .TE
  42 .hy
  43 .ad
  44 .sp 1
  45 .SH STANDARDS
  46 POSIX.1-2001, POSIX.1-2008.
  47 .SH NOTES
  48 On Linux,
  49 .BR sleep ()
  50 is implemented via
  51 .BR nanosleep (2).
  52 See the
  53 .BR nanosleep (2)
  54 man page for a discussion of the clock used.
  55 .SS Portability notes
  56 On some systems,
  57 .BR sleep ()
  58 may be implemented using
  59 .BR alarm (2)
  60 and
  61 .B SIGALRM
  62 (POSIX.1 permits this);
  63 mixing calls to
  64 .BR alarm (2)
  65 and
  66 .BR sleep ()
  67 is a bad idea.
  68 .PP
  69 Using
  70 .BR longjmp (3)
  71 from a signal handler or modifying the handling of
  72 .B SIGALRM
  73 while sleeping will cause undefined results.
  74 .SH SEE ALSO
  75 .BR sleep (1),
  76 .BR alarm (2),
  77 .BR nanosleep (2),
  78 .BR signal (2),
  79 .BR signal (7)