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RocketLink!--> Man page versions: OpenBSD FreeBSD NetBSD RedHat Solaris Others

GETITIMER(2)              OpenBSD Programmer's Manual             GETITIMER(2)

     getitimer, setitimer - get/set value of interval timer

     #include <sys/time.h>

     #define ITIMER_REAL      0
     #define ITIMER_VIRTUAL   1
     #define ITIMER_PROF      2

     getitimer(int which, struct itimerval *value);

     setitimer(int which, const struct itimerval *value,
             struct itimerval *ovalue);

     The system provides each process with three interval timers, defined in
     <sys/time.h>. The getitimer() call returns the current value for the
     timer specified in which in the structure at value. The setitimer() call
     sets a timer to the specified value (returning the previous value of the
     timer if ovalue is non-null).

     A timer value is defined by the itimerval structure:

           struct itimerval {
                   struct  timeval it_interval;    /* timer interval */
                   struct  timeval it_value;       /* current value */

     If it_value is non-zero, it indicates the time to the next timer expira-
     tion.  If it_interval is non-zero, it specifies a value to be used in
     reloading it_value when the timer expires.  Setting it_value to 0 dis-
     ables a timer.  Setting it_interval to 0 causes a timer to be disabled
     after its next expiration (assuming it_value is non-zero).

     Time values smaller than the resolution of the system clock are rounded
     up to this resolution (typically 10 milliseconds).

     The ITIMER_REAL timer decrements in real time.  A SIGALRM signal is de-
     livered when this timer expires.

     The ITIMER_VIRTUAL timer decrements in process virtual time.  It runs on-
     ly when the process is executing.  A SIGVTALRM signal is delivered when
     it expires.

     The ITIMER_PROF timer decrements both in process virtual time and when
     the system is running on behalf of the process.  It is designed to be
     used by interpreters in statistically profiling the execution of inter-
     preted programs.  Each time the ITIMER_PROF timer expires, the SIGPROF
     signal is delivered.  Because this signal may interrupt in-progress sys-
     tem calls, programs using this timer must be prepared to restart inter-
     rupted system calls.

     Five macros for manipulating time values are defined in <sys/time.h>:

     timerclear(struct timeval *)
           Sets a time value to zero.

     timerisset(struct timeval *)

           Tests if a time value is non-zero.

     timercmp(struct timeval *a, struct timeval *b, CMP)
           Compares two time values in the form a CMP b, where CMP is <, =, or
           > (beware that >= and <= do not work with this macro).

     timersub(struct timeval *a, struct timeval *b, struct timeval *res)
           Subtracts a - b and stores the result in res.

     timeradd(struct timeval *a, struct timeval *a, struct timeval *res)
           Adds two timers and stores the result in res.

     If the calls succeed, a value of 0 is returned.  If an error occurs, the
     value -1 is returned, and a more precise error code is placed in the
     global variable errno.

     getitimer() and setitimer() will fail if:

     [EFAULT]      The value parameter specified a bad address.

     [EINVAL]      A value parameter specified a time that was too large to be

     gettimeofday(2),  poll(2),  select(2),  sigaction(2)

     The getitimer() function call appeared in 4.2BSD.

OpenBSD 2.6                    December 11, 1993                             2

Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY
SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts
Institute of Technology, Free Software Foundation, FreeBSD Inc., and others.

(Corrections, notes, and links courtesy of RocketAware.com)

[Detailed Topics]

[Overview Topics]

Up to: Real-Time related - time of day, elapsed time, sleeping, waiting for events. time(), gmtime(), localtime(), etc.
Up to: Process Signals and Events - Sending and handling signals and events.

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