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)