usleep (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Sin...
NAME
usleep - suspend execution for microsecond intervalsSYNOPSIS
#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
- EINTR
- Interrupted by a signal; see signal(7).
- EINVAL
- usec is not smaller than 1000000. (On systems where that is considered an error.)
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| usleep() | Thread safety | MT-Safe |
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.