Thread: Executing more than one command with fork() and exec()

The following program:

Code:

#include <stdlib.h>
#include <stdio.h>

int main(void) {
    int status = system("ls /");
    
    if (status == -1) {
        fputs("Error when creating child process or retrieving its exit status.\n", stderr);
    }
    else {
        printf("Child process exited with exit status %d\n", status);
    }
    
    return 0;
}

Is roughly equivalent to the following one using fork() and exec():

Code:

#define _POSIX_C_SOURCE 200809L

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

int main(void) {
    pid_t pid = fork();
    
    switch (pid) {
        case -1: // Couldn't create process
            fputs("Couldn't create another process\n", stderr);
            break;
        
        case 0: // Child process
            execlp("ls", "ls", "/", (char *)0);
            fputs("Couldn't replace the child process image\n", stderr);
            break;
            
        default: // Parent process
            ;
            int status;
            pid_t wpid = wait(&status);
            if (wpid == pid) {
                printf("Child process exited with exit status %d\n", status);
            }
    }
    
    return 0;
}

But how could this one be rewritten using fork() and exec()?

Code:

#include <stdlib.h>
#include <stdio.h>

void printstatus(int status) {
    if (status == -1) {
        fputs("Error when creating child process or retrieving its exit status.\n", stderr);
    }
    else {
        printf("Child process exited with exit status %d\n", status);
    }
}

int main(void) {
    int status = system("ls /");
    printstatus(status);
    
    status = system("ls /tmp");
    printstatus(status);
    
    return 0;
}

Basically my question is how to create a second fork of the process and change its flow so that it executes a different command. Or better still, how to create a fork and execute a command specified in an arbitrary string the same way it is passed to system() as an argument.

Oh, so the child process' instructions begin at the point where the fork() function was called..... I was expecting it to begin from main(), so I was overcomplicating stuff!!