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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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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 greater than or equal to 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 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/.
2017-09-15 USLEEP(3)
Pages that refer to this page: free(1), gawk(1), clock_nanosleep(2), getitimer(2), nanosleep(2), select(2), __ppc_get_timebase(3), ualarm(3), signal(7), time(7)
Copyright and license for this manual page
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