USLEEP(3) Linux Programmer's Manual USLEEP(3)
NAME
usleep - suspend execution for microsecond intervals
SYNOPSIS
#include <unistd.h>
int usleep(useconds_t usec);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
usleep():
Since glibc 2.12:
_BSD_SOURCE ||
(_XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
!(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
Before glibc 2.12:
_BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
DESCRIPTION
The usleep() function suspends execution of the calling process for (at
least) usec 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.
RETURN VALUE
0 on success, -1 on error.
ERRORS
EINTR Interrupted by a signal; see signal(7).
EINVAL usec is not smaller than 1000000. (On systems where that is
considered an error.)
CONFORMING TO
4.3BSD, POSIX.1-2001. POSIX.1-2001 declares this function obsolete;
use nanosleep(2) instead. POSIX.1-2008 removes the specification of
usleep().
On the original BSD implementation, and in glibc before version 2.2.2,
the return type of this function is void. The POSIX version returns
int, and this is also the prototype used since glibc 2.2.2.
Only the EINVAL error return is documented by SUSv2 and POSIX.1-2001.
NOTES
The type 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
#include <unistd.h>
...
unsigned int usecs;
...
usleep(usecs);
The interaction of this function with the SIGALRM signal, and with
other timer functions such as alarm(2), sleep(3), nanosleep(2),
setitimer(2), timer_create(2), timer_delete(2), timer_getoverrun(2),
timer_gettime(2), timer_settime(2), ualarm(3) is unspecified.
SEE ALSO
alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
sleep(3), ualarm(3), time(7)
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2010-09-20 USLEEP(3)
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