NAME

       sleep - sleep for a specified number of seconds

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <unistd.h>

       unsigned int sleep(unsigned int seconds);

DESCRIPTION

       sleep()  causes  the  calling thread to sleep either until the number of real-time seconds
       specified in seconds have elapsed or until a signal arrives which is not ignored.

RETURN VALUE

       Zero if the requested time has elapsed, or the number of seconds left  to  sleep,  if  the
       call was interrupted by a signal handler.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────┬───────────────┬─────────────────────────────┐
       │Interface                                  │ Attribute     │ Value                       │
       ├───────────────────────────────────────────┼───────────────┼─────────────────────────────┤
       │sleep()                                    │ Thread safety │ MT-Unsafe sig:SIGCHLD/linux │
       └───────────────────────────────────────────┴───────────────┴─────────────────────────────┘

VERSIONS

       On  Linux,  sleep()  is implemented via nanosleep(2).  See the nanosleep(2) man page for a
       discussion of the clock used.

       On some systems, sleep() may be implemented using alarm(2) and  SIGALRM  (POSIX.1  permits
       this); mixing calls to alarm(2) and sleep() is a bad idea.

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001.

CAVEATS

       Using longjmp(3) from a signal handler or modifying the handling of SIGALRM while sleeping
       will cause undefined results.

SEE ALSO

       sleep(1), alarm(2), nanosleep(2), signal(2), signal(7)