trusty (3) getitimer.3posix.gz

Provided by: manpages-posix-dev_2.16-1_all bug

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_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.

       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.

       The interaction between setitimer() and any of alarm(), sleep(), or usleep() 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
       None.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       alarm() , sleep()  ,  timer_getoverrun()  ,  ualarm()  ,  usleep()  ,  the  Base  Definitions  volume  of
       IEEE Std 1003.1-2001, <signal.h>, <sys/time.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .