This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

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

       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 http://www.opengroup.org/unix/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                                   2017                                     GETITIMER(3POSIX)

       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.

       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.

       Thefollowingsectionsareinformative.

       None.

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

       getitimer, setitimer — get and set value of interval timer

       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.

       None.

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

alarm(), exec, sleep(), timer_getoverrun()

       The Base Definitions volume of POSIX.1‐2017, <signal.h>, <sys_time.h>

       #include <sys/time.h>

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