Unix/Linux Go Back    


OpenDarwin 7.2.1 - man page for setitimer (opendarwin section 2)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


GETITIMER(2)			     BSD System Calls Manual			     GETITIMER(2)

NAME
     getitimer, setitimer -- get/set value of interval timer

SYNOPSIS
     #include <sys/time.h>
     #define ITIMER_REAL      0
     #define ITIMER_VIRTUAL   1
     #define ITIMER_PROF      2

     int
     getitimer(int which, struct itimerval *value);

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

DESCRIPTION
     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-nil).

     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 expiration.  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 disables a timer.  Setting it_interval to 0 causes a timer to be dis-
     abled 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 resolu-
     tion (typically 10 milliseconds).

     The ITIMER_REAL timer decrements in real time.  A SIGALRM signal is delivered when this
     timer expires.

     The ITIMER_VIRTUAL timer decrements in process virtual time.  It runs only 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 pro-
     filing the execution of interpreted programs.  Each time the ITIMER_PROF timer expires, the
     SIGPROF signal is delivered.  Because this signal may interrupt in-progress system calls,
     programs using this timer must be prepared to restart interrupted system calls.

NOTES
     Three macros for manipulating time values are defined in <sys/time.h>.  Timerclear sets a
     time value to zero, timerisset tests if a time value is non-zero, and timercmp compares two
     time values (beware that >= and <= do not work with this macro).

RETURN VALUES
     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.

ERRORS
     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 handled.

SEE ALSO
     select(2), sigaction(2), gettimeofday(2)

HISTORY
     The getitimer() function call appeared in 4.2BSD.

4.2 Berkeley Distribution		December 11, 1993		4.2 Berkeley Distribution
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 03:08 AM.