External Command Execution

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

#define MAX_ARGS 10

int main() {
    char command[100];
    char *args[MAX_ARGS];
    pid_t pid;

    printf("Enter command: ");
    fgets(command, sizeof(command), stdin);

    // Remove trailing newline from the input
    command[strcspn(command, "\n")] = 0;

    // Tokenize the command and arguments
    char *token = strtok(command, " ");
    int argc = 0;
    while (token != NULL && argc < MAX_ARGS - 1) {
        args[argc++] = token;
        token = strtok(NULL, " ");
    }
    args[argc] = NULL; // Null-terminate the argument list

    // Check if the command contains a path separator
    if (strchr(args[0], '/') != NULL) {
        // Command contains an absolute path
        pid = fork();
        if (pid == -1) {
            perror("fork");
            exit(EXIT_FAILURE);
        } else if (pid == 0) {
            // Child process
            execv(args[0], args);
            perror("execv");
            exit(EXIT_FAILURE);
        } else {
            // Parent process
            wait(NULL); // Wait for child to finish
        }
    } else {
        // Command does not contain an absolute path
        // Search for the command in PATH
        char *path = getenv("PATH");
        if (path == NULL) {
            fprintf(stderr, "PATH environment variable not found.\n");
            exit(EXIT_FAILURE);
        }

        char *path_copy = strdup(path);
        token = strtok(path_copy, ":");
        while (token != NULL) {
            // Construct the full path
            char full_path[100];
            snprintf(full_path, sizeof(full_path), "%s/%s", token, args[0]);

            // Check if the file exists
            if (access(full_path, X_OK) == 0) {
                pid = fork();
                if (pid == -1) {
                    perror("fork");
                    exit(EXIT_FAILURE);
                } else if (pid == 0) {
                    // Child process
                    execv(full_path, args);
                    perror("execv");
                    exit(EXIT_FAILURE);
                } else {
                    // Parent process
                    wait(NULL); // Wait for child to finish
                    break; // Exit loop since command was found and executed
                }
            }
            token = strtok(NULL, ":");
        }
        free(path_copy);

        if (token == NULL) {
            // Command not found in PATH
            fprintf(stderr, "Command not found.\n");
            exit(EXIT_FAILURE);
        }
    }

    return 0;
}