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)):
- 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
Interrupted by a signal; see signal(7).
usec is greater than or equal to 1000000. (On systems where
that is considered an error.)
On the original BSD implementation, and in glibc before version
2.2.2, the return type of this function is
void. The POSIX
int, and this is also the prototype used since
Only the EINVAL error return is documented by SUSv2 and POSIX.1-2001.
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.
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