Write a C program (time_pipe.c) that determines the amount of time necessary to run a command from the command line

This program will be run as ./time and will report the amount of elapsed time to run the specified command

. This will involve using fork() and execvp() functions, as well as the gettimeofday() function to determine the elapsed time. It will also require the use of two different IPC mechanisms.

The general strategy is to fork a child process that will execute the specified command. However, before the child executes the command, it will record a timestamp of the current time (which we term starting time). The parent process will wait for the child process to terminate. Once the child terminates, the parent will record the current timestamp for the ending time. The difference between the starting and ending times represents the elapsed time to execute the command

The second, time_pipe.c, version will use a pipe. The child will write the starting time to the pipe, and the parent will read from it following the termination of the child process

You will use the gettimeofday() function to record the current timestamp. This function is passed a pointer to a struct timeval object, which contains two members: tv_sec and tv_usec. These represent the number of elapsed seconds and microseconds since January 1, 1970 (known as the UNIX EPOCH). The following code sample illustrates how this function can be used:

// Get current time timeval_t startTime; gettimeofday( &startTime, 0 );

// get the end time timeval_t end_time; gettimeofday( &end_time, 0 );

// calculate elapsed time timeval_t elapsed_time; timersub( &end_time, startTime, &elapsed_time );

// print elapsed time (microseconds right justified zero filled) printf( " Elapsed time: %d.%06d seconds ", elapsed_time.tv_sec, elapsed_time.tv_usec );