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  2003-07-23 "" "Linux Programmer's Manual"
  32 .SH NAME
  33 usleep \- suspend execution for microsecond intervals
  34 .SH SYNOPSIS
  35 .nf
  36 /* BSD version */
  37 .B "#include <unistd.h>"
  38 .sp
  39 .BI "void usleep(unsigned long " usec );
  40 .sp
  41 /* SUSv2 version */
  42 .B "#define _XOPEN_SOURCE 500"
  43 .br
  44 .B "#include <unistd.h>"
  45 .sp
  46 .BI "int usleep(useconds_t " usec ");
  47 .fi
  48 .SH DESCRIPTION
  49 The \fBusleep\fP() function suspends execution of the calling process for
  50 (at least) \fIusec\fP microseconds.  The sleep may be lengthened slightly
  51 by any system activity or by the time spent processing the call or by the
  52 granularity of system timers.
  53 .SH "RETURN VALUE"
  54 None (BSD). Or: 0 on success, \-1 on error (SUSv2).
  55 .SH ERRORS
  56 .TP
  57 EINTR
  58 Interrupted by a signal.
  59 .TP
  60 EINVAL
  61 \fIusec\fP is not smaller than 1000000.
  62 (On systems where that is considered an error.)
  63 .SH "CONFORMING TO"
  64 4.3BSD.
  65 The SUSv2 version returns int, and this is also the prototype
  66 used by glibc 2.2.2.
  67 Only the EINVAL error return is documented by SUSv2.
  68 .SH NOTES
  69 The type
  70 .B useconds_t
  71 is an unsigned integer type capable of holding integers
  72 in the range [0,1000000]. Programs will be more portable
  73 if they never mention this type explicitly. Use
  74 .RS
  75 .nf
  76 .ta 8
  77 .sp
  78 #include <unistd.h>
  79 \&...
  80         unsigned int usecs;
  81 \&...
  82         usleep(usecs);
  83 .sp
  84 .fi
  85 .RE
  86 This type is defined by
  87 .I <sys/types.h>
  88 included by
  89 .I <unistd.h>
  90 but glibc defines it only when _XOPEN_SOURCE has a value not less than 500,
  91 or both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined.
  92 .\" useconds_t also gives problems on HPUX 10.
  93 .LP
  94 The interaction of this function with the SIGALRM signal, and with
  95 other timer functions such as
  96 .IR alarm (),
  97 .IR sleep (),
  98 .IR nanosleep (),
  99 .IR setitimer (),
 100 .IR timer_create (),
 101 .IR timer_delete (),
 102 .IR timer_getoverrun (),
 103 .IR timer_gettime (),
 104 .IR timer_settime (),
 105 .IR ualarm ()
 106 is unspecified.
 107 .LP
 108 This function is obsolete. Use
 109 .BR nanosleep (2)
 110 or
 111 .BR setitimer (2)
 112 instead.
 113 .SH "SEE ALSO"
 114 .BR alarm (2),
 115 .BR getitimer (2),
 116 .BR nanosleep (2),
 117 .BR select (2),
 118 .BR setitimer (2),
 119 .BR sleep (3)