PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

GETITIMER(3P)             POSIX Programmer's Manual            GETITIMER(3P)

PROLOG         top

       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         top

       getitimer, setitimer — get and set value of interval timer

SYNOPSIS         top

       #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         top

       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         top

       Upon successful completion, getitimer() or setitimer() shall return
       0; otherwise, −1 shall be returned and errno set to indicate the
       error.

ERRORS         top

       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         top

       None.

APPLICATION USAGE         top

       Applications should use the timer_gettime() and timer_settime()
       functions instead of the obsolescent getitimer() and setitimer()
       functions, respectively.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       The getitimer() and setitimer() functions may be removed in a future
       version.

SEE ALSO         top

       alarm(3p), exec(1p), sleep(3p), timer_getoverrun(3p)

       The Base Definitions volume of POSIX.1‐2008, signal.h(0p),
       sys_time.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                       GETITIMER(3P)