USLEEP(3) Linux Programmer's Manual USLEEP(3)
usleep - suspend execution for microsecond intervals
int usleep(useconds_t usec);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
Since glibc 2.12:
(_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
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.)
Multithreading (see pthreads(7))
The usleep() function is thread-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.
unsigned int 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),
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