Question

At a high level, how would you use the execve() function to write a duplicate of the ls program in UNIX? I am doing an exercise to familiarize myself with the exec() family of functions, command-line arguments, and environment variables. I am not familiar with using these concepts, however I know what they do.

Answer 1

The code below can excute ls command. Do you mean this?

#include <stdio.h>

int main(void)
{
        system("ls");
        return 0;
}

And I wrote a simple ls demo for you.

my_ls.c

#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>

int main(int argc, char *argv[])
{
        if (argc != 2) {
                return 0;
        }

        DIR *dir = opendir(argv[1]);
        if (dir) {
                struct dirent *s_dir;
                while((s_dir = readdir(dir))) {
                        printf("%s ", s_dir->d_name);
                }
                printf("\n");
        }

        return 0;
}

Usage:

gcc my_ls.c -o my_ls
./my_ls .