usleep(3)

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

6       usleep - suspend execution for microsecond intervals
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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       int usleep(useconds_t usec);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       usleep():
19           Since glibc 2.12:
20               (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
21                   || /* glibc >= 2.19: */ _DEFAULT_SOURCE
22                   || /* glibc <= 2.19: */ _BSD_SOURCE
23           Before glibc 2.12:
24               _BSD_SOURCE || _XOPEN_SOURCE >= 500
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DESCRIPTION

27       The  usleep() function suspends execution of the calling thread for (at
28       least) usec microseconds.  The sleep may be lengthened slightly by  any
29       system  activity  or  by  the  time spent processing the call or by the
30       granularity of system timers.
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RETURN VALUE

33       The usleep() function returns 0 on success.  On error, -1 is  returned,
34       with errno set to indicate the error.
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ERRORS

37       EINTR  Interrupted by a signal; see signal(7).
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39       EINVAL usec  is  greater  than  or equal to 1000000.  (On systems where
40              that is considered an error.)
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ATTRIBUTES

43       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
44       tributes(7).
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46       ┌────────────────────────────────────────────┬───────────────┬─────────┐
47       │Interface                                   │ Attribute     │ Value   │
48       ├────────────────────────────────────────────┼───────────────┼─────────┤
49       │usleep()                                    │ Thread safety │ MT-Safe │
50       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

53       None.
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HISTORY

56       4.3BSD,  POSIX.1-2001.   POSIX.1-2001  declares it obsolete, suggesting
57       nanosleep(2) instead.  Removed in POSIX.1-2008.
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59       On the original BSD implementation, and before glibc 2.2.2, the  return
60       type of this function is void.  The POSIX version returns int, and this
61       is also the prototype used since glibc 2.2.2.
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63       Only the EINVAL error return is documented by SUSv2 and POSIX.1-2001.
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CAVEATS

66       The interaction of this function with the SIGALRM signal, and with oth‐
67       er   timer   functions   such   as  alarm(2),  sleep(3),  nanosleep(2),
68       setitimer(2),  timer_create(2),  timer_delete(2),  timer_getoverrun(2),
69       timer_gettime(2), timer_settime(2), ualarm(3) is unspecified.
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