table of contents
USLEEP(3) | Linux Programmer's Manual | USLEEP(3) |
NAME¶
usleep - suspend execution for microsecond intervals
SYNOPSIS¶
#include <unistd.h> int usleep(useconds_t usec);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
usleep():
- Since glibc 2.12:
-
_BSD_SOURCE ||
(_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
DESCRIPTION¶
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.
RETURN VALUE¶
The usleep() function returns 0 on success. On error, -1 is returned, with errno set to indicate the cause of the error.
ERRORS¶
CONFORMING TO¶
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.
NOTES¶
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.
SEE ALSO¶
alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2), sleep(3), ualarm(3), time(7)
COLOPHON¶
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
2013-04-19 |