sleep(3) - f38

1sleep(3)                   Library Functions Manual                   sleep(3)
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NAME

6       sleep - sleep for a specified number of seconds
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <unistd.h>
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14       unsigned int sleep(unsigned int seconds);
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DESCRIPTION

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

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

26       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
27       tributes(7).
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29       ┌────────────────────────┬───────────────┬─────────────────────────────┐
30       │Interface               │ Attribute     │ Value                       │
31       ├────────────────────────┼───────────────┼─────────────────────────────┤
32       │sleep()                 │ Thread safety │ MT-Unsafe sig:SIGCHLD/linux │
33       └────────────────────────┴───────────────┴─────────────────────────────┘
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VERSIONS

36       On   Linux,   sleep()   is   implemented  via  nanosleep(2).   See  the
37       nanosleep(2) man page for a discussion of the clock used.
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39       On some systems, sleep() may be implemented using alarm(2) and  SIGALRM
40       (POSIX.1  permits  this); mixing calls to alarm(2) and sleep() is a bad
41       idea.
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STANDARDS

44       POSIX.1-2008.
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HISTORY

47       POSIX.1-2001.
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CAVEATS

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