man3/usleep.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  30 .\" Modified 2001-04-01 by aeb
  31 .\" Modified 2003-07-23 by aeb
  32 .\"
  33 .TH USLEEP 3  2013-04-19 "" "Linux Programmer's Manual"
  34 .SH NAME
  35 usleep \- suspend execution for microsecond intervals
  36 .SH SYNOPSIS
  37 .nf
  38 .B "#include <unistd.h>"
  39 .sp
  40 .BI "int usleep(useconds_t " usec );
  41 .fi
  42 .sp
  43 .in -4n
  44 Feature Test Macro Requirements for glibc (see
  45 .BR feature_test_macros (7)):
  46 .in
  47 .sp
  48 .BR usleep ():
  49 .ad l
  50 .RS 4
  51 .PD 0
  52 .TP 4
  53 Since glibc 2.12:
  54 .nf
  55 _BSD_SOURCE ||
  56     (_XOPEN_SOURCE\ >=\ 500 ||
  57         _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED) &&
  58     !(_POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700)
  59 .TP 4
  60 .fi
  61 Before glibc 2.12:
  62 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
  63 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  64 .PD
  65 .RE
  66 .ad b
  67 .SH DESCRIPTION
  68 The
  69 .BR usleep ()
  70 function suspends execution of the calling thread for
  71 (at least) \fIusec\fP microseconds.
  72 The sleep may be lengthened slightly
  73 by any system activity or by the time spent processing the call or by the
  74 granularity of system timers.
  75 .SH RETURN VALUE
  76 The
  77 .BR usleep ()
  78 function returns 0 on success.
  79 On error, \-1 is returned, with
  80 .I errno
  81 set to indicate the cause of the error.
  82 .SH ERRORS
  83 .TP
  84 .B EINTR
  85 Interrupted by a signal; see
  86 .BR signal (7).
  87 .TP
  88 .B EINVAL
  89 \fIusec\fP is not smaller than 1000000.
  90 (On systems where that is considered an error.)
  91 .SH CONFORMING TO
  92 4.3BSD, POSIX.1-2001.
  93 POSIX.1-2001 declares this function obsolete; use
  94 .BR nanosleep (2)
  95 instead.
  96 POSIX.1-2008 removes the specification of
  97 .BR usleep ().
  98
  99 On the original BSD implementation,
 100 and in glibc before version 2.2.2, the return type of this function is
 101 .IR void .
 102 The POSIX version returns
 103 .IR int ,
 104 and this is also the prototype used since glibc 2.2.2.
 105
 106 Only the
 107 .B EINVAL
 108 error return is documented by SUSv2 and POSIX.1-2001.
 109 .SH NOTES
 110 The type
 111 .I useconds_t
 112 is an unsigned integer type capable of holding integers
 113 in the range [0,1000000].
 114 Programs will be more portable
 115 if they never mention this type explicitly.
 116 Use
 117 .in +4n
 118 .nf
 119 .sp
 120 #include <unistd.h>
 121 \&...
 122     unsigned int usecs;
 123 \&...
 124     usleep(usecs);
 125 .fi
 126 .in
 127 .LP
 128 The interaction of this function with the
 129 .B SIGALRM
 130 signal, and with other timer functions such as
 131 .BR alarm (2),
 132 .BR sleep (3),
 133 .BR nanosleep (2),
 134 .BR setitimer (2),
 135 .BR timer_create (2),
 136 .BR timer_delete (2),
 137 .BR timer_getoverrun (2),
 138 .BR timer_gettime (2),
 139 .BR timer_settime (2),
 140 .BR ualarm (3)
 141 is unspecified.
 142 .SH SEE ALSO
 143 .BR alarm (2),
 144 .BR getitimer (2),
 145 .BR nanosleep (2),
 146 .BR select (2),
 147 .BR setitimer (2),
 148 .BR sleep (3),
 149 .BR ualarm (3),
 150 .BR time (7)