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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:
             (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
                 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
                 || /* Glibc versions <= 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 cause of 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 |
     +----------+---------------+---------+

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.