clock_gettime time elapsed code example

Example: clock_gettime example

/*
 * This program calculates the time required to
 * execute the program specified as its first argument.
 * The time is printed in seconds, on standard out.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>

#define BILLION  1000000000L;

int main( int argc, char **argv )
  {
    struct timespec start, stop;
    double accum;

    if( clock_gettime( CLOCK_REALTIME, &start) == -1 ) {
      perror( "clock gettime" );
      exit( EXIT_FAILURE );
    }

    system( argv[1] );

    if( clock_gettime( CLOCK_REALTIME, &stop) == -1 ) {
      perror( "clock gettime" );
      exit( EXIT_FAILURE );
    }

    accum = ( stop.tv_sec - start.tv_sec )
          + ( stop.tv_nsec - start.tv_nsec )
            / BILLION;
    printf( "%lf\n", accum );
    return( EXIT_SUCCESS );
  }
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