Formatted signal names

[thirdparty/man-pages.git] / man3 / usleep.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2001-04-01 by aeb
.\" Modified 2003-07-23 by aeb
.\"
.TH USLEEP 3  2007-02-01 "" "Linux Programmer's Manual"
.SH NAME
usleep \- suspend execution for microsecond intervals
.SH SYNOPSIS
.nf
.B "#define _XOPEN_SOURCE 500     /* Or: #define _BSD_SOURCE */"
.br
.B "#include <unistd.h>"
.sp
.BI "int usleep(useconds_t " usec );
.fi
.SH DESCRIPTION
The
.BR usleep ()
function suspends execution of the calling process for
(at least) \fIusec\fP microseconds.
The sleep may be lengthened slightly
by any system activity or by the time spent processing the call or by the
granularity of system timers.
.SH "RETURN VALUE"
0 on success, \-1 on error.
.SH ERRORS
.TP
EINTR
Interrupted by a signal.
.TP
EINVAL
\fIusec\fP is not smaller than 1000000.
(On systems where that is considered an error.)
.SH "CONFORMING TO"
4.3BSD, POSIX.1-2001.
POSIX.1-2001 declares this function obsolete; use
.BR nanosleep (2)
instead.

On the original BSD implementation,
and in glibc before version 2.2.2, the return type of this function is
.IR void .
The POSIX version returns
.IR int ,
and this is also the prototype used since glibc 2.2.2.

Only the EINVAL error return is documented by SUSv2.
.SH NOTES
The type
.B useconds_t
is an unsigned integer type capable of holding integers
in the range [0,1000000].
Programs will be more portable
if they never mention this type explicitly.
Use
.RS
.nf
.ta 8
.sp
#include <unistd.h>
\&...
    unsigned int usecs;
\&.
    usleep(usecs);
.fi
.RE
.LP
The interaction of this function with the
.B SIGALRM
signal, and with other timer functions such as
.BR alarm (2),
.BR sleep (3),
.BR nanosleep (2),
.BR setitimer (2),
.BR timer_create (3),
.BR timer_delete (3),
.BR timer_getoverrun (3),
.BR timer_gettime (3),
.BR timer_settime (3),
.BR ualarm (3)
is unspecified.
.SH "SEE ALSO"
.BR alarm (2),
.BR getitimer (2),
.BR nanosleep (2),
.BR select (2),
.BR setitimer (2),
.BR ualarm (3),
.BR sleep (3),
.BR feature_test_macros (7),
.BR time (7)