Name

usleep — suspend execution for microsecond intervals

Synopsis

#include <unistd.h>
int usleep( useconds_t   usec);
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
usleep():
_BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION

The usleep() function suspends execution of the calling process 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

0 on success, −1 on error.

ERRORS

EINTR

Interrupted by a signal.

EINVAL

usec is not smaller than 1000000. (On systems where that is considered an error.)

CONFORMING TO

4.3BSD, POSIX.1-2001. POSIX.1-2001 declares this function obsolete; use nanosleep(2) instead.

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.

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(3), timer_delete(3), timer_getoverrun(3), timer_gettime(3), timer_settime(3), ualarm(3) is unspecified.

SEE ALSO

alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2), ualarm(3), sleep(3), time(7)

COLOPHON

This page is part of release 2.79 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/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified 1993-07-24 by Rik Faith (faithcs.unc.edu)
Modified 2001-04-01 by aeb
Modified 2003-07-23 by aeb