man3/usleep.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  28 .\" Modified 2001-04-01 by aeb
  29 .\" Modified 2003-07-23 by aeb
  30 .\"
  31 .TH USLEEP 3  2007-02-01 "" "Linux Programmer's Manual"
  32 .SH NAME
  33 usleep \- suspend execution for microsecond intervals
  34 .SH SYNOPSIS
  35 .nf
  36 .B "#define _XOPEN_SOURCE 500     /* Or: #define _BSD_SOURCE */"
  37 .br
  38 .B "#include <unistd.h>"
  39 .sp
  40 .BI "int usleep(useconds_t " usec );
  41 .fi
  42 .SH DESCRIPTION
  43 The
  44 .BR usleep ()
  45 function suspends execution of the calling process for
  46 (at least) \fIusec\fP microseconds.
  47 The sleep may be lengthened slightly
  48 by any system activity or by the time spent processing the call or by the
  49 granularity of system timers.
  50 .SH "RETURN VALUE"
  51 0 on success, \-1 on error.
  52 .SH ERRORS
  53 .TP
  54 .B EINTR
  55 Interrupted by a signal.
  56 .TP
  57 .B EINVAL
  58 \fIusec\fP is not smaller than 1000000.
  59 (On systems where that is considered an error.)
  60 .SH "CONFORMING TO"
  61 4.3BSD, POSIX.1-2001.
  62 POSIX.1-2001 declares this function obsolete; use
  63 .BR nanosleep (2)
  64 instead.
  65
  66 On the original BSD implementation,
  67 and in glibc before version 2.2.2, the return type of this function is
  68 .IR void .
  69 The POSIX version returns
  70 .IR int ,
  71 and this is also the prototype used since glibc 2.2.2.
  72
  73 Only the
  74 .B EINVAL
  75 error return is documented by SUSv2.
  76 .SH NOTES
  77 The type
  78 .B useconds_t
  79 is an unsigned integer type capable of holding integers
  80 in the range [0,1000000].
  81 Programs will be more portable
  82 if they never mention this type explicitly.
  83 Use
  84 .RS
  85 .nf
  86 .ta 8
  87 .sp
  88 #include <unistd.h>
  89 \&...
  90     unsigned int usecs;
  91 \&.
  92     usleep(usecs);
  93 .fi
  94 .RE
  95 .LP
  96 The interaction of this function with the
  97 .B SIGALRM
  98 signal, and with other timer functions such as
  99 .BR alarm (2),
 100 .BR sleep (3),
 101 .BR nanosleep (2),
 102 .BR setitimer (2),
 103 .BR timer_create (3),
 104 .BR timer_delete (3),
 105 .BR timer_getoverrun (3),
 106 .BR timer_gettime (3),
 107 .BR timer_settime (3),
 108 .BR ualarm (3)
 109 is unspecified.
 110 .SH "SEE ALSO"
 111 .BR alarm (2),
 112 .BR getitimer (2),
 113 .BR nanosleep (2),
 114 .BR select (2),
 115 .BR setitimer (2),
 116 .BR ualarm (3),
 117 .BR sleep (3),
 118 .BR feature_test_macros (7),
 119 .BR time (7)