// caller.c
#include <stdio.h>
#include <unistd.h>

int main() {
    printf("--- In caller.c ---\n");
    printf("This message is from the original program.\n");
    printf("Calling execve to run './callee'...\n\n");

    // Arguments for the new program
    // The first argument is conventionally the program name
    char *argv[] = { "./callee", "first_arg", "second_arg", NULL };

    // Environment variables for the new program
    char *envp[] = { "CUSTOM_VAR=Hello from caller!", "ANOTHER_VAR=123", NULL };

    // The execve system call
    // The first argument is the path to the executable
    // The second is the array of arguments
    // The third is the array of environment variables
    execve("callee.", argv, envp);

    // This part of the code will only be reached if execve fails
    perror("execve failed");
    return 1;
}