Open Source Software

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  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.

SEE ALSO

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

COLOPHON

   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at
   https://www.kernel.org/doc/man-pages/.

                              2016-03-15                         USLEEP(3)



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