getitimer(3p) — Linux manual page


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

       An XSI-conforming implementation provides each process with at
       least three interval timers, which are indicated by the which

       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.

                     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

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



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

RATIONALE         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.1‐2017, signal.h(0p),

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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 .

IEEE/The Open Group               2017                     GETITIMER(3P)

Pages that refer to this page: sys_time.h(0p)alarm(3p)exec(3p)pselect(3p)setitimer(3p)sleep(3p)