Section (3) ualarm
Name
ualarm — schedule signal after given number of microseconds
Synopsis
#include <unistd.h>
useconds_t
ualarm( |
useconds_t usecs, |
useconds_t interval) ; |
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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
orinterval
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_settime(2), usleep(3) is unspecified.
This function is obsolete. Use setitimer(2) or POSIX interval timers (timer_create(2), etc.) instead.
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/.
Copyright (c) 2003 Andries Brouwer (aebcwi.nl) %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License_zsingle_quotesz_s references to object code and executables are to be interpreted as the output of any document formatting or typesetting system, including intermediate and printed output. This manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this manual; if not, see <http://www.gnu.org/licenses/>. %%%LICENSE_END |