ualarm(3)

1UALARM(3)                  Linux Programmer's Manual                 UALARM(3)
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NAME

6       ualarm - schedule signal after given number of microseconds
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SYNOPSIS

9       #include <unistd.h>
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11       useconds_t ualarm(useconds_t usecs, useconds_t interval);
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13   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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15       ualarm():
16           Since glibc 2.12:
17               _BSD_SOURCE ||
18                   (_XOPEN_SOURCE >= 500 ||
19                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
20                   !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
21           Before glibc 2.12:
22               _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
23               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
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DESCRIPTION

26       The ualarm() function causes the signal  SIGALRM  to  be  sent  to  the
27       invoking  process  after (not less than) usecs microseconds.  The delay
28       may be lengthened slightly by any system activity or by the time  spent
29       processing the call or by the granularity of system timers.
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31       Unless  caught  or  ignored,  the  SIGALRM  signal  will  terminate the
32       process.
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34       If the interval argument is nonzero, further SIGALRM  signals  will  be
35       sent every interval microseconds after the first.
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RETURN VALUE

38       This  function  returns  the  number  of microseconds remaining for any
39       alarm that was previously set, or 0 if no alarm was pending.
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ERRORS

42       EINTR  Interrupted by a signal.
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44       EINVAL usecs or interval is not  smaller  than  1000000.   (On  systems
45              where that is considered an error.)
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CONFORMING TO

48       4.3BSD,   POSIX.1-2001.    POSIX.1-2001  marks  ualarm()  as  obsolete.
49       POSIX.1-2008 removes the specification of ualarm().  4.3BSD, SUSv2, and
50       POSIX do not define any errors.
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NOTES

53       POSIX.1-2001  does not specify what happens if the usecs argument is 0.
54       On Linux (and probably most other systems), the effect is to cancel any
55       pending alarm.
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57       The  type  useconds_t  is  an  unsigned integer type capable of holding
58       integers in the range [0,1000000].  On the original BSD implementation,
59       and in glibc before version 2.1, the arguments to ualarm() were instead
60       typed as unsigned int.  Programs will be more portable  if  they  never
61       mention useconds_t explicitly.
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63       The  interaction  of  this  function with other timer functions such as
64       alarm(2),  sleep(3),   nanosleep(2),   setitimer(2),   timer_create(2),
65       timer_delete(2),   timer_getoverrun(2),   timer_gettime(2),  timer_set‐
66       time(2), usleep(3) is unspecified.
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68       This function is obsolete.  Use setitimer(2) or POSIX  interval  timers
69       (timer_create(2), etc.)  instead.
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COLOPHON

76       This page is part of release 3.53 of the Linux  man-pages  project.   A
77       description  of  the project, and information about reporting bugs, can
78       be found at http://www.kernel.org/doc/man-pages/.
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82                                  2013-04-18                         UALARM(3)