68 lines
2.6 KiB
Groff
68 lines
2.6 KiB
Groff
.TH GETITIMER 2 "April 14, 2006"
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.UC 4
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.SH NAME
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getitimer, setitimer \- get and set value of interval timer
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.SH SYNOPSIS
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.nf
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.ft B
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#include <sys/time.h>
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int getitimer(int \fIwhich\fP, struct itimerval *\fIvalue\fP)
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.in +5
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.ti -5
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int setitimer(int \fIwhich\fP, const struct itimerval *\fIvalue\fP, struct itimerval *\fIovalue\fP);
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.in -5
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.ft R
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.fi
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.SH DESCRIPTION
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.B Getitimer
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retrieves the current value of the given interval timer, in \fIvalue\fP.
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.PP
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.B Setitimer
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sets a new value for the given interval timer, as given in \fIvalue\fP, and, if \fIovalue\fP is not set to
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.BR NULL ,
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stores the old value for the interval timer in \fIovalue\fP.
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.PP
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For both functions, the \fIwhich\fP parameter indicates which of the interval timers they work on; \fIwhich\fP can have one of the following values:
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.PP
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.TP 15
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.B ITIMER_REAL
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A timer that is decremented in realtime. When it expires, a
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.BR SIGARLM
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signal is delivered to the process.
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.TP
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.B ITIMER_VIRTUAL
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A timer that is decremented in process user time. When it expires, a
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.BR SIGVTALRM
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signal is delivered to the process.
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.TP
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.B ITIMER_PROF
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A timer that is decremented in process user+system time. When it expires, a
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.BR SIGPROF
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signal is delivered to the process.
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.PP
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The specified timer will first expire after the time specified in the 'it_value' field of the itimerval structure. Similarly, upon retrieval the 'it_value' field will contain the time after which the timer will expire.
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.PP
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If 'it_value' is zero, then the timer is disabled, and the 'it_interval' field is ignored and (upon retrieval) set to zero. Otherwise, 'it_interval' contains the repetition interval after which the timer will repeatedly expire, starting from the moment that the timer expires for the first time according to the 'it_value' value. If 'it_interval' is set to zero, no repetition will occur.
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.PP
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The maximum supported timeout value that
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.B setitimer
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accepts, depends on the clock tick rate of the operating system.
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.PP
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These functions share their real-time timer with
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.BR alarm (2).
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Therefore, use of both types of functions in one program yields undefined results.
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.SH RETURN VALUES
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Upon successful completion, these functions return 0. Otherwise, a value of -1 is returned and \fIerrno\fP is set to indicate the error.
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.SH ERRORS
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The functions will fail if any of the following occur:
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.TP 15
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.B EINVAL
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Either \fIwhich\fP is not one of the ITIMER_* constants above, or one of the timeval structures in \fIvalue\fP contains a bad or too large value.
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.TP
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.B EFAULT
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Bad \fIvalue\fP or \fIovalue\fP address.
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.SH SEE ALSO
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.BR alarm (2)
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.SH AUTHOR
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David van Moolenbroek <dcvmoole@cs.vu.nl>
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