*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->OpenBSD man pages -> timerisset (3)              



NAME    [Toc]    [Back]

     getitimer, setitimer - get/set value of interval timer

SYNOPSIS    [Toc]    [Back]

     #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);

     timerclear(struct timeval *);

     timerisset(struct timeval *);

     timercmp(struct timeval *a, struct timeval *b, CMP);

     timersub(struct  timeval  *a,  struct  timeval  *b,   struct
timeval *res);

     timeradd(struct   timeval  *a,  struct  timeval  *b,  struct
timeval *res);

DESCRIPTION    [Toc]    [Back]

     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 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 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 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 profiling  the  execution of interpreted
  programs.   Each time the ITIMER_PROF timer expires,
     signal is delivered.  Because this signal may interrupt  inprogress system
  calls,  programs  using  this timer must be prepared to
restart interrupted
 system calls.

     The remaining five functions are in fact macros for  manipulating time
     values, defined in <sys/time.h>.

     timerclear(a) sets the time value in a to zero.

     timerisset(a) tests if the time value in a is non-zero.

     timercmp(a,  b,  CMP) compares two time values in the form a
CMP b, where
     CMP is <, <=, ==, !=, >=, or > .

     timersub(a, b, res) subtracts a - b and stores the result in

     timeradd(a, b, res) adds two timers and stores the result in

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     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

SEE ALSO    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

     The getitimer() function call appeared in 4.2BSD.

OpenBSD      3.6                        December     11,     1993
[ Back ]
 Similar pages
Name OS Title
getitimer Linux get or set value of an interval timer
setitimer HP-UX get and set value of interval timer
ualarm HP-UX set the interval timer
getitimer HP-UX get and set value of interval timer
nanosleep Tru64 Suspends a process from execution for the specified timer interval (P1003.1b)
gettimer Tru64 Get value of a per-process timer
timers HP-UX timer operations
timer_gettime HP-UX timer operations
timer_settime HP-UX timer operations
timer_getoverrun HP-UX timer operations
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service