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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).

       ┌──────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────┼───────────────┼─────────┤
       │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

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       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)