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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.
SEE ALSO
       BR alarm  (2),  getitimer(2),  nanosleep(2),  select(2),  setitimer(2),
       sleep(3), ualarm(3), time(7)
COLOPHON
       This  page  is  part of release 4.15 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/.
                                  2017-09-15                         USLEEP(3)