# getitimer

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           getitimer, setitimer — get and set value of interval timer
    


## SYNOPSIS



           #include <sys/time.h>
    
           int getitimer(int _which_ , struct itimerval *_value_);
           int setitimer(int _which_ , const struct itimerval *restrict _value_ ,
               struct itimerval *restrict _ovalue_);
    


## DESCRIPTION



           The _getitimer_() function shall store the current value of the
           timer specified by _which_ into the structure pointed to by _value_.
           The _setitimer_() function shall set the timer specified by _which_ to
           the value specified in the structure pointed to by _value_ , and if
           _ovalue_ is not a null pointer, store the previous value of the
           timer in the structure pointed to by _ovalue_.
    
           A timer value is defined by the **itimerval** structure, specified in
           _< sys/time.h>_.  If _it_value_ is non-zero, it shall indicate the time
           to the next timer expiration.  If _it_interval_ is non-zero, it
           shall specify a value to be used in reloading _it_value_ when the
           timer expires. Setting _it_value_ to 0 shall disable a timer,
           regardless of the value of _it_interval_.  Setting _it_interval_ to 0
           shall disable a timer after its next expiration (assuming _it_value_
           is non-zero).
    
           Implementations may place limitations on the granularity of timer
           values. For each interval timer, if the requested timer value
           requires a finer granularity than the implementation supports, the
           actual timer value shall be rounded up to the next supported
           value.
    
           An XSI-conforming implementation provides each process with at
           least three interval timers, which are indicated by the _which_
           argument:
    
           ITIMER_PROF   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 interpreted programs.
                         Each time the ITIMER_PROF timer expires, the SIGPROF
                         signal is delivered.
    
           ITIMER_REAL   Decrements in real time. A SIGALRM signal is
                         delivered when this timer expires.
    
           ITIMER_VIRTUAL
                         Decrements in process virtual time. It runs only
                         when the process is executing. A SIGVTALRM signal is
                         delivered when it expires.
    
           The interaction between _setitimer_() and _alarm_() or _sleep_() is
           unspecified.
    


## RETURN VALUE



           Upon successful completion, _getitimer_() or _setitimer_() shall
           return 0; otherwise, -1 shall be returned and _errno_ set to
           indicate the error.
    


## ERRORS



           The _setitimer_() function shall fail if:
    
           **EINVAL** The _value_ argument is not in canonical form. (In canonical
                  form, the number of microseconds is a non-negative integer
                  less than 1000000 and the number of seconds is a non-
                  negative integer.)
    
           The _getitimer_() and _setitimer_() functions may fail if:
    
           **EINVAL** The _which_ argument is not recognized.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           Applications should use the _timer_gettime_() and _timer_settime_()
           functions instead of the obsolescent _getitimer_() and _setitimer_()
           functions, respectively.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           The _getitimer_() and _setitimer_() functions may be removed in a
           future version.
    


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