Question

Programming in C (not C++)

## Requirements

Only need to edit the challenge.c

You have one function to implement: void fork_exec(char** argv):
This takes in an array of strings representing arguments.
The first argument is the filename of an executable (which will be given as a relative filepath, such as "./a")
The remaining terms would be arguments for said executable.
The array is null terminated
You need to fork your process.
The child needs to call exec (rather, a variant thereof) to execute the specified file with the specified arguments.

challenge.c

#include "challenge.h"

// goal: fork the process and have the child execute a process
// param argv: the argument vector for the process to be executed
// assumptions:
//   the first argument of argv is the file name of the executable
//   argv is null terminated
//
// TODO: complete the function
//   fork
//   exec (child), probably most convenient to use execvp
//   have the parent wait on the child
void fork_exec(char** argv)
{

}

challenge.h

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

#ifndef CH_HEAD
#define CH_HEAD

// goal: fork the process and have the child execute a process
// param argv: the argument vector for the process to be executed
// assumptions:
//   the first argument of argv is the file name of the executable
//   argv is null terminated
void fork_exec(char** argv);

#endif

Answer 1

Summary: The program starts from main and it will call an executable called ./exec. The program to create ./exec is also pasted here for the reference. The challenge.c forkexec method will create a child process and the child will execute the ./exec program. The parent will wait for the child to get finished. The output is pasted at the end.

Challenge.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "challenge.h"

// goal: fork the process and have the child execute a process
// param argv: the argument vector for the process to be executed
// assumptions:
//   the first argument of argv is the file name of the executable
//   argv is null terminated
//
// TODO: complete the function
//   fork
//   exec (child), probably most convenient to use execvp
//   have the parent wait on the child
void forkexec(char** argv)
{
        pid_t childPid;
        childPid = fork();
    // The fork() method will return 0 in the child process
        if(childPid == 0) {
        // Now we are in the child process
        printf("Child process id: %d PID: %d\n", getppid(), getpid());
        execvp(argv[0],argv);
          }
          else if(childPid > 0) {
        // The fork() method will return > 0 in the parent process
            printf("Parent process id: %d\n", getpid());
            printf("Waiting for child process to terminate.\n");
        // Wait for the child to terminate
            wait(NULL);
            printf("Child process completed.\n");
          }
          else {
            printf("Unable to create child process.\n");
          }
 
}

int main() 
{ 
        char *argv[]={"./exec", "I am a child process!!!", NULL}; 
    // Call the fork method
        forkexec(argv);
    return 0; 
} 

Creating a file exec.c

#include<stdio.h> 
#include<unistd.h> 
  
int main(int argc, char *argv[]) 
{ 
    // This will be called by the child process
    printf("\nIn Child process\n"); 
    printf("Program name is: %s\n", argv[0]);  
    printf("First argument is: %s\n", argv[1]); 
      
    return 0; 
} 

This will create a executable exec file