usleep(3C)

NAME

     usleep - suspend execution for interval in microseconds

SYNOPSIS

     #include <unistd.h>

     int usleep(useconds_t useconds);

DESCRIPTION

     The usleep() function suspends the caller from execution for
     the  number  of microseconds specified by the useconds argu-
     ment. (A microsecond is .000001 seconds.) Because  of  other
     activity,  or  because  of  the time spent in processing the
     call, the actual suspension time  may  be  longer  than  the
     amount of time specified.

     If the value of useconds is 0, then the call has no effect.

     In a single-threaded program (one not linked  with  -lthread
     or  -lpthread),  the  usleep()  function  uses the process's
     realtime interval timer to indicate to the system  when  the
     process should be woken up.

     There is one real-time interval timer for each process.  The
     usleep() function will not interfere with a previous setting
     of this timer.  If the process has set this timer  prior  to
     calling  usleep(),  and  if  the  time specified by useconds
     equals or exceeds the interval timer's  prior  setting,  the
     caller  will be woken up shortly before the timer was set to
     expire.

     Interactions  between  usleep()  and  either   alarm(2)   or
     sleep(3C) are unspecified.

     In a multithreaded program  (one  linked  with  -lthread  or
     -lpthread),   usleep()   is   implemented   by   a  call  to
     nanosleep(3RT) and does not modify the state  of  the  alarm
     signal or the realtime interval timer.  There is no interac-
     tion between this version of usleep() and either alarm(2) or
     sleep(3C).

RETURN VALUES

     On completion,  usleep()  returns  0.  There  are  no  error
     retruns.

ERRORS

     No errors are returned.

USAGE

     The usleep() function is included for its historical  usage.
     The nanosleep(3RT) function is preferred over this function.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | Safe                        |
    |_____________________________|_____________________________|

SEE ALSO

     alarm(2),   setitimer(2),   sigaction(2),    sigprocmask(2),
     nanosleep(3RT), sleep(3C), ualarm(3C), attributes(5)

NOTES

     In a multithreaded program,  only  the  invoking  thread  is
     suspended from execution.