计算C中程序的执行时间

Question

I want to calculate and print the time taken by my C program to execute using ftime() specifically..

I am seeing the man page for ftime() but I don't understand how to use it!

Answer 1

As @KamilCuk correctly mentioned, ftime() is deprecated and should be displaced with clock_gettime(), see the man page .

This and more examples explained here

#include <stdio.h>
#include <time.h>      // for clock_t, clock()
#include <unistd.h>    // for sleep()
 
#define BILLION  1000000000.0
 
// main function to find the execution time of a C program
int main()
{
    struct timespec start, end;
 
    clock_gettime(CLOCK_REALTIME, &start);
 
    // do some stuff here
    sleep(3);
 
    clock_gettime(CLOCK_REALTIME, &end);
 
    // time_spent = end - start
    double time_spent = (end.tv_sec - start.tv_sec) +
                        (end.tv_nsec - start.tv_nsec) / BILLION;
 
    printf("Time elpased is %f seconds", time_spent);
 
    return 0;
}

Answer 2

1. If you're in Linux, just use 'time' command to measure the program execution time:

time ./my_programm

2. Here some code with clock_gettime()

#include <stdio.h> //For printf
#include <time.h>  //For clock_gettime

int main (void)
{  
   //Structs for saving timestamps
   struct timespec mt1, mt2; 
   //Variable for time delta calculating 
   long int tt;      
   
   //Get current time
   clock_gettime (CLOCK_REALTIME, &mt1);

   /* do some stuff here */

   //Get current time again
   clock_gettime (CLOCK_REALTIME, &mt2);

   //Calculate the delta between two timestamps
   tt=1000000000*(mt2.tv_sec - mt1.tv_sec)+(mt2.tv_nsec - mt1.tv_nsec);

   //Print the delta
   printf ("Time spent: %ld nsec / %ld ms\n", tt, tt/1000000);

   return 0;
}