getitimer()--Get Value for Interval Timer

 #include <sys/time.h>

 int getitimer( int which, struct itimerval *value );   

The getitimer() function returns the value last used to set the interval timer specified by which in the structure pointed to by value.

Authorities and Locks

None.

Parameters

which

(Input) The interval timer type.

The possible values for which, which are defined in the <sys/time.h> header file, are as follows:

ITIMER_REAL	The interval timer value is decremented in real time. The SIGALRM signal is generated for the process when this timer expires.
ITIMER_VIRTUAL	The interval timer value is only decremented when the process is running. The SIGVTALRM signal is generated for the process when this timer expires.
ITIMER_PROF	The interval timer value is only decremented when the process is running or when the system is running on behalf of the process. The SIGPROF signal is generated for the process when this timer expires.

value

(Output) A pointer to the space where the current interval timer value is stored.

Return Value

Error Conditions

If getitimer() is not successful, errno usually indicates the following error. Under some conditions, errno could indicate an error other than that listed here.

[EINVAL]

The value specified for the argument is not correct.

A function was passed incorrect argument values, or an operation was attempted on an object and the operation specified is not supported for that type of object.

An argument value is not valid, out of range, or NULL.

• The value of which is not equal to one of the defined values.

[ENOTSIGINIT]

Process not enabled for signals.

An attempt was made to call a signal function under one of the following conditions:

• The signal function is being called for a process that is not enabled for asynchronous signals.
• The signal function is being called when the system signal controls have not been initialized.

Related Information

• The <sys/time.h> file (see Header Files for UNIX-Type Functions)
  
  
• alarm()--Set Schedule for Alarm Signal
  
  
• setitimer()--Set Value for Interval Timer
  
  
• sleep()--Suspend Processing for Interval of Time
  
  
• usleep()--Suspend Processing for Interval of Time

Example

See Code disclaimer information for information pertaining to code examples.

The following example returns the current interval timer value using the getitimer() function:

#include <sys/time.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <errno.h>

#define LOOP_LIMIT  1E12

volatile int sigcount=0;

void catcher( int sig ) {

    struct itimerval value;
    int which = ITIMER_REAL;

    printf( "Signal catcher called for signal %d\n", sig );
    sigcount++;

    if( sigcount > 1 ) {

        /*
         * Disable the real time interval timer
         */

        getitimer( which, &value );

        value.it_value.tv_sec = 0;
        value.it_value.tv_usec = 0;

        setitimer( which, &value, NULL );
    }
}

int main( int argc, char *argv[] ) {

    int result = 0;

    struct itimerval value, ovalue, pvalue;
    int which = ITIMER_REAL;

    struct sigaction sact;
    volatile double count;
    time_t t;

    sigemptyset( &sact.sa_mask );
    sact.sa_flags = 0;
    sact.sa_handler = catcher;
    sigaction( SIGALRM, &sact, NULL );

    getitimer( which, &pvalue );

    /*
     * Set a real time interval timer to repeat every 200 milliseconds
     */

    value.it_interval.tv_sec = 0;        /* Zero seconds */
    value.it_interval.tv_usec = 200000;  /* Two hundred milliseconds */
    value.it_value.tv_sec = 0;           /* Zero seconds */
    value.it_value.tv_usec = 500000;     /* Five hundred milliseconds */

    result = setitimer( which, &value, &ovalue );

    /*
     * The interval timer value returned by setitimer() should be
     * identical to the timer value returned by getitimer().
     */

    if( ovalue.it_interval.tv_sec != pvalue.it_interval.tv_sec  ||
        ovalue.it_interval.tv_usec != pvalue.it_interval.tv_usec ||
        ovalue.it_value.tv_sec != pvalue.it_value.tv_sec ||
        ovalue.it_value.tv_usec != pvalue.it_value.tv_usec ) {
        printf( "Real time interval timer mismatch\n" );
        result = -1;
    }


    time( &t );
    printf( "Before loop, time is %s", ctime(&t) );

    for( count=0; ((count<LOOP_LIMIT) && (sigcount<2)); count++ );

    time( &t );
    printf( "After loop, time is %s\n", ctime(&t) );


    if( sigcount == 0 )
        printf( "The signal catcher never gained control\n" );
    else
        printf( "The signal catcher gained control\n" );

    printf( "The value of count is %.0f\n", count );

    return( result );
}

Output:

    Before loop, time is Sun Jun 15 10:14:00 1997
    Signal catcher called for signal 14
    Signal catcher called for signal 14
    After loop, time is Sun Jun 15 10:14:01 1997
    The signal catcher gained control
    The value of count is 702943