请写一个c 语言程序，模拟实现一个简单的二级文件管理系统，要求做到以下几点： （1）可以实现常用文件目录和文件操作，如： login 用户登录 dir 列文件目录 create 创建文件 delete 删除文件 open 打开文件 close 关闭文件 read 读文件 write 写文件 （2）列目录时要列出文件名、物理地址、保护码和文件长度 （3）源文件可以进行读写保护

好的，以下是一个简单的二级文件管理系统的 C 语言程序，实现了常用的文件目录和文件操作，并且支持读写保护：

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

#define MAX_FILE_NAME_LENGTH 20
#define MAX_FILE_COUNT 100

struct file {
    char name[MAX_FILE_NAME_LENGTH];
    int address;
    int protection;
    int length;
    int is_open;
    char *content;
};

struct directory {
    char name[MAX_FILE_NAME_LENGTH];
    int file_count;
    struct file files[MAX_FILE_COUNT];
};

struct user {
    char name[MAX_FILE_NAME_LENGTH];
    int is_logged_in;
    struct directory directories[2];
};

struct user users[2] = {
    {"user1", 0, {{"dir1", 0, {}}, {"dir2", 0, {}}}},
    {"user2", 0, {{"dir1", 0, {}}, {"dir2", 0, {}}}}
};

int current_user_index = -1;
int current_directory_index = -1;

void print_error(char *message) {
    printf("Error: %s\n", message);
}

void print_success(char *message) {
    printf("Success: %s\n", message);
}

void login() {
    char username[MAX_FILE_NAME_LENGTH];
    printf("Enter username: ");
    scanf("%s", username);
    int user_found = 0;
    for (int i = 0; i < 2; i++) {
        if (strcmp(users[i].name, username) == 0) {
            current_user_index = i;
            user_found = 1;
            break;
        }
    }
    if (!user_found) {
        print_error("User not found");
        return;
    }
    users[current_user_index].is_logged_in = 1;
    printf("Logged in as %s\n", username);
}

void logout() {
    if (current_user_index == -1) {
        print_error("You are not logged in");
        return;
    }
    users[current_user_index].is_logged_in = 0;
    current_user_index = -1;
    current_directory_index = -1;
    printf("Logged out\n");
}

void select_directory() {
    if (current_user_index == -1) {
        print_error("You are not logged in");
        return;
    }
    char directory_name[MAX_FILE_NAME_LENGTH];
    printf("Enter directory name: ");
    scanf("%s", directory_name);
    int directory_found = 0;
    for (int i = 0; i < 2; i++) {
        if (strcmp(users[current_user_index].directories[i].name, directory_name) == 0) {
            current_directory_index = i;
            directory_found = 1;
            break;
        }
    }
    if (!directory_found) {
        print_error("Directory not found");
        return;
    }
    printf("Selected directory %s\n", directory_name);
}

void dir() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    printf("%-20s%-20s%-20s%-20s\n", "Name", "Address", "Protection", "Length");
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        struct file file = users[current_user_index].directories[current_directory_index].files[i];
        printf("%-20s%-20d%-20d%-20d\n", file.name, file.address, file.protection, file.length);
    }
}

void create() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            print_error("File already exists");
            return;
        }
    }
    struct file new_file;
    strcpy(new_file.name, file_name);
    new_file.address = rand() % 1000;
    new_file.protection = rand() % 2;
    new_file.length = 0;
    new_file.is_open = 0;
    new_file.content = NULL;
    users[current_user_index].directories[current_directory_index].files[users[current_user_index].directories[current_directory_index].file_count] = new_file;
    users[current_user_index].directories[current_directory_index].file_count++;
    print_success("File created");
}

void delete() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    int file_found = 0;
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            if (users[current_user_index].directories[current_directory_index].files[i].is_open) {
                print_error("File is open");
                return;
            }
            free(users[current_user_index].directories[current_directory_index].files[i].content);
            for (int j = i; j < users[current_user_index].directories[current_directory_index].file_count - 1; j++) {
                users[current_user_index].directories[current_directory_index].files[j] = users[current_user_index].directories[current_directory_index].files[j + 1];
            }
            users[current_user_index].directories[current_directory_index].file_count--;
            file_found = 1;
            break;
        }
    }
    if (!file_found) {
        print_error("File not found");
        return;
    }
    print_success("File deleted");
}

void open() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    int file_index = -1;
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            file_index = i;
            break;
        }
    }
    if (file_index == -1) {
        print_error("File not found");
        return;
    }
    if (users[current_user_index].directories[current_directory_index].files[file_index].is_open) {
        print_error("File is already open");
        return;
    }
    users[current_user_index].directories[current_directory_index].files[file_index].is_open = 1;
    users[current_user_index].directories[current_directory_index].files[file_index].content = malloc(sizeof(char));
    printf("File opened\n");
}

void close() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    int file_index = -1;
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            file_index = i;
            break;
        }
    }
    if (file_index == -1) {
        print_error("File not found");
        return;
    }
    if (!users[current_user_index].directories[current_directory_index].files[file_index].is_open) {
        print_error("File is not open");
        return;
    }
    users[current_user_index].directories[current_directory_index].files[file_index].is_open = 0;
    free(users[current_user_index].directories[current_directory_index].files[file_index].content);
    printf("File closed\n");
}

void read() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    int file_index = -1;
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            file_index = i;
            break;
        }
    }
    if (file_index == -1) {
        print_error("File not found");
        return;
    }
    if (!users[current_user_index].directories[current_directory_index].files[file_index].is_open) {
        print_error("File is not open");
        return;
    }
    if (users[current_user_index].directories[current_directory_index].files[file_index].protection == 1) {
        print_error("You do not have permission to read this file");
        return;
    }
    printf("%s\n", users[current_user_index].directories[current_directory_index].files[file_index].content);
}

void write() {
    if (current_directory_index == -1) {
        print_error("No directory selected");
        return;
    }
    char file_name[MAX_FILE_NAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", file_name);
    int file_index = -1;
    for (int i = 0; i < users[current_user_index].directories[current_directory_index].file_count; i++) {
        if (strcmp(users[current_user_index].directories[current_directory_index].files[i].name, file_name) == 0) {
            file_index = i;
            break;
        }
    }
    if (file_index == -1) {
        print_error("File not found");
        return;
    }
    if (!users[current_user_index].directories[current_directory_index].files[file_index].is_open) {
        print_error("File is not open");
        return;
    }
    if (users[current_user_index].directories[current_directory_index].files[file_index].protection == 1) {
        print_error("You do not have permission to write to this file");
        return;
    }
    char *content = malloc(sizeof(char));
    printf("Enter file content: ");
    scanf("%s", content);
    users[current_user_index].directories[current_directory_index].files[file_index].content = content;
    users[current_user_index].directories[current_directory_index].files[file_index].length = strlen(content);
    print_success("File written");
}

int main() {
    while (1) {
        printf("Enter command: ");
        char command[MAX_FILE_NAME_LENGTH];
        scanf("%s", command);
        if (strcmp(command, "login") == 0) {
            login();
        } else if (strcmp(command, "logout") == 0) {
            logout();
        } else if (strcmp(command, "select") == 0) {
            select_directory();
        } else if (strcmp(command, "dir") == 0) {
            dir();
        } else if (strcmp(command, "create") == 0) {
            create();
        } else if (strcmp(command, "delete") == 0) {
            delete();
        } else if (strcmp(command, "open") == 0) {
            open();
        } else if (strcmp(command, "close") == 0) {
            close();
        } else if (strcmp(command, "read") == 0) {
            read();
        } else if (strcmp(command, "write") == 0) {
            write();
        } else {
            print_error("Command not recognized");
        }
    }
    return 0;
}

注意：这只是一个简单的示例程序，实际的文件管理系统可能更为复杂，需要考虑更多的安全性和性能问题。