usleep

Section: C Library Functions (3)
Updated: 2023-02-05
Index Return to Main Contents
 

NAME

usleep - suspend execution for microsecond intervals  

LIBRARY

Standard C library (libc, -lc)  

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:
        (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
            || /* glibc >= 2.19: */ _DEFAULT_SOURCE
            || /* glibc <= 2.19: */ _BSD_SOURCE
    Before glibc 2.12:
        _BSD_SOURCE || _XOPEN_SOURCE >= 500
 

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 error.  

ERRORS

EINTR
Interrupted by a signal; see signal(7).
EINVAL
usec is greater than or equal to 1000000. (On systems where that is considered an error.)
 

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
usleep() Thread safetyMT-Safe

 

STANDARDS

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 before glibc 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 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), useconds_t(3type), time(7)

 

Index

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
NOTES
SEE ALSO
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Time: 10:23:55 GMT, April 27, 2024