noble (3) usleep.3.gz

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).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                     │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │usleep()                                                                      │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       None.

HISTORY

       4.3BSD, POSIX.1-2001.  POSIX.1-2001 declares it obsolete, suggesting nanosleep(2)  instead.   Removed  in
       POSIX.1-2008.

       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.

CAVEATS

       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)