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Write a C program that behaves like a shell which displays the command prompt ‘myshell$’. It accepts the command, tokenize the command line and execute it by creating the child process. Also implement the additional command ‘list’ as myshell$ list f dirname: It will display filenames in a given directory. myshell$ list n dirname: It will count the number of entries in a given directory. myshell$ list i dirname: It will display filenames and their inode number for the files in a given directory.




 #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <dirent.h>
#include <sys/stat.h>
#include <fcntl.h>

#define MAX_INPUT_SIZE 1024
#define MAX_ARGS 10

void execute_command(char *args[], int count) {
    pid_t pid = fork();
    if (pid == -1) {
        perror("fork failed");
        exit(EXIT_FAILURE);
    } else if (pid == 0) {
        // Child process
        execvp(args[0], args);
        perror("execvp failed");
        exit(EXIT_FAILURE);
    } else {
        // Parent process
        wait(NULL); // Wait for the child to complete
    }
}

void list_files(char *dirname, char *option) {
    struct dirent *entry;
    DIR *dir = opendir(dirname);
    if (dir == NULL) {
        perror("opendir");
        return;
    }

    while ((entry = readdir(dir)) != NULL) {
        if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
            char full_path[MAX_INPUT_SIZE];
            sprintf(full_path, "%s/%s", dirname, entry->d_name);

            struct stat file_stat;
            if (stat(full_path, &file_stat) == 0) {
                if (strcmp(option, "f") == 0) {
                    printf("%s\n", entry->d_name); // Display filenames
                } else if (strcmp(option, "n") == 0) {
                    // Count the number of entries
                } else if (strcmp(option, "i") == 0) {
                    printf("%s (Inode: %ld)\n", entry->d_name, file_stat.st_ino); // Display filenames and inode numbers
                }
            }
        }
    }

    closedir(dir);
}

int main() {
    char input[MAX_INPUT_SIZE];
    char *args[MAX_ARGS];
    int arg_count;

    while (1) {
        printf("myshell$ ");
        if (fgets(input, sizeof(input), stdin) == NULL) {
            break; // Exit the loop on EOF
        }

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

        // Tokenize the input
        arg_count = 0;
        char *token = strtok(input, " ");
        while (token != NULL) {
            args[arg_count] = token;
            arg_count++;
            token = strtok(NULL, " ");
        }
        args[arg_count] = NULL; // Null-terminate the argument list

        // Handle the "list" command
        if (arg_count >= 3 && strcmp(args[0], "list") == 0) {
            list_files(args[2], args[1]);
        } else {
            execute_command(args, arg_count);
        }
    }

    return 0;
}

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