USLEEP
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Page Index
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:
-
(_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
- Before glibc 2.12:
-
_BSD_SOURCE || _XOPEN_SOURCE >= 500
DESCRIPTION
The
usleep()
function suspends execution of the calling thread 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
The
usleep()
function returns 0 on success.
On error, -1 is returned, with
errno
set to indicate the cause of the error.
ERRORS
- EINTR
-
Interrupted by a signal; see
signal(7).
- EINVAL
-
usec is greater than or equal to 1000000.
(On systems where that is considered an error.)
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
usleep()
| Thread safety | MT-Safe
|
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 5.10 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.