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man:ualarm

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

NAME

     ualarm - schedule signal after given number of microseconds

SYNOPSIS

     #include <unistd.h>
     useconds_t ualarm(useconds_t usecs, useconds_t interval);
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     ualarm():
         Since glibc 2.12:
             (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
                 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
                 || /* Glibc versions <= 2.19: */ _BSD_SOURCE
         Before glibc 2.12:
             _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION

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

RETURN VALUE

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

ERRORS

     EINTR  Interrupted by a signal; see signal(7).
     EINVAL usecs  or  interval  is  not  smaller than 1000000.  (On systems
            where that is considered an error.)

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     +----------+---------------+---------+
     |Interface | Attribute     | Value   |
     +----------+---------------+---------+
     |ualarm()  | Thread safety | MT-Safe |
     +----------+---------------+---------+

CONFORMING TO

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

NOTES

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

SEE ALSO

     alarm(2),    getitimer(2),   nanosleep(2),   select(2),   setitimer(2),
     usleep(3), time(7)

COLOPHON

     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.
                                2017-09-15                         UALARM(3)
/data/webs/external/dokuwiki/data/pages/man/ualarm.txt · Last modified: 2019/05/17 09:32 by 127.0.0.1

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