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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
USLEEP(3) Linux Programmer's Manual USLEEP(3)
usleep - suspend execution for microsecond intervals
#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
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.
The usleep() function returns 0 on success. On error, -1 is
returned, with errno set to indicate the cause of the error.
EINTR Interrupted by a signal; see signal(7).
EINVAL usec is not smaller than 1000000. (On systems where that is
considered an error.)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────┼───────────────┼─────────┤
│usleep() │ Thread safety │ MT-Safe │
└──────────┴───────────────┴─────────┘
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.
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.
alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
sleep(3), ualarm(3), time(7)
This page is part of release 4.12 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/.
2016-03-15 USLEEP(3)
Pages that refer to this page: free(1), gawk(1), clock_nanosleep(2), getitimer(2), nanosleep(2), select_tut(2), __ppc_get_timebase(3), ualarm(3), signal(7), time(7)