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

       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

       getitimer, setitimer - get and set value of interval timer

       #include <sys/time.h>

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

       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:

              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.

              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.

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

       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.





       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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The original Standard can be
       obtained online at .

IEEE/The Open Group                  2003                        GETITIMER(3P)