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) && ! (_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
() function suspends execution of the calling thread for (at
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.
() function returns 0 on success. On error, -1 is returned,
set to indicate the cause of the error.
- Interrupted by a signal; see signal(7).
- 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)
4.3BSD, POSIX.1-2001. POSIX.1-2001 declares this function obsolete; use
instead. POSIX.1-2008 removes the specification of
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
, 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
unsigned int usecs;
The interaction of this function with the SIGALRM
signal, and with other
timer functions such as alarm(2)
BR alarm (2), getitimer(2)
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