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<html><!-- This HTML file has been created by texi2html 1.29
from syscalls.texi on 4 June 1994 -->
<TITLE>Syscall specifications of Linux - getitimer</TITLE>
<P>Go to the <A HREF="syscalls_86.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_86.html">previous</A>, <A HREF="syscalls_88.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_88.html">next</A> section.<P>
<H2><A NAME="SEC87" HREF="syscalls_toc.html#SEC87" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_toc.html#SEC87">getitimer and setitimer</A></H2>
<P>
<H3>SYNOPSIS</H3>
<P>
<CODE>int getitimer(int <VAR>which</VAR>, struct itimerval *<VAR>value</VAR>);</CODE>
<P>
<CODE>int setitimer(int <VAR>which</VAR>, const struct itimerval *<VAR>value</VAR>,
struct itimerval *<VAR>ovalue</VAR>);</CODE>
<P>
<H3>PARAMETERS</H3>
<P>
<VAR>which</VAR>: [in] the timer to access.
<P>
<VAR>value</VAR>: (For <CODE>getitimer</CODE>) [out] the value of the timer. (For
<CODE>setitimer</CODE>) [in] the new value of the timer.
<P>
<VAR>ovalue</VAR>: [out] the old value of the timer.
<P>
<H3>DESCRIPTION</H3>
<P>
Each task posess 3 interval timers:
<P>
<DL COMPACT>
<DT><CODE>ITIMER_REAL</CODE>
<DD>Real time timer. It delivers <CODE>SIGALRM</CODE> upon expiration.
<P>
<DT><CODE>ITIMER_VIRTUAL</CODE>
<DD>Runs only during the time the task is actually running on the processor.
It delivers <CODE>SIGVTALRM</CODE> upon expiration.
<P>
<DT><CODE>ITIMER_PROF</CODE>
<DD>Runs only during the time the taks is actually running on the processor
or during the operating system is running on behalf of the task. It
delivers <CODE>SIGPROF</CODE> upon expiration.
</DL>
<P>
The structure <CODE>itimerval</CODE> has the following structure:
<P>
<PRE>
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
</PRE>
<P>
<PRE>
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* microseconds */
};
</PRE>
<P>
<CODE>getitimer</CODE> gets those values for a specific timer and
<CODE>setitimer</CODE> sets those values for a specific timer (and also
retrieve the old values). If <CODE>it_value</CODE> or <CODE>it_interval</CODE> is
set to 0 the timer is deactivated. The timers always expire at or after
the requested time. If the requesting process is active at the moment of
expiration a signal is immediately delivered otherwise the delivery may
be delayed.
<P>
<H3>RETURN VALUE</H3>
<P>
On success zero is returned. On error -1 is returned and <CODE>errno</CODE> is
set to one of the following values:
<P>
<UL>
<LI><CODE>EINVAL</CODE>: <VAR>which</VAR> has an invalid value.
<LI><CODE>EFAULT</CODE>.
</UL>
<P>
<P>Go to the <A HREF="syscalls_86.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_86.html">previous</A>, <A HREF="syscalls_88.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_88.html">next</A> section.<P>