12_arg

...
int main() // 省略参数列表
{
	...
}

...
int main(int argc, char *argv[]) {}
// 或者
int main(int argc, char **argv) {}

#include <iostream>

int main(int argc, char *argv[])
{
    std::cout << "Number of arguments = " << argc << std::endl;

    for (int i=0; i<argc; ++i)
    {
        std::cout << "Argument " << i << ": "
            << argv[i] << std::endl;
    }

    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main(int argc, char *argv[])
{
    std::cout << "Number of arguments = " << argc << std::endl;

    for (int i = 0; i < argc; ++i)
    {
        std::cout << "Argument " << i << ": "
                  << argv[i] << std::endl;
    }

    // 如果没有额外命令行参数，执行此判断
    if (argc < 2) {
        cout << "Usage: " << argv[0] << " <filename> [mode]" << endl;
        cout << "Modes: read (default), write" << endl;
        return 1;
    }
    
    string filename = argv[1];
    string mode = (argc > 2) ? argv[2] : "read"; // 缺省mode设置为read
    
    if (mode == "read") { // 实现read模式
        ifstream file(filename);
        if (!file) { // 错误判断
            cout << "Error: Cannot open file " << filename << endl;
            return 1; // 终止程序
        }
        
        string line;
        cout << "File content:" << endl;
        // 输出文件中所有line
        while (getline(file, line)) {
            cout << line << endl;
        }
        file.close();
        
    } else if (mode == "write") { // 实现write模式
        ofstream file(filename, ios::app); // Append mode
        if (!file) { // 错误判断
            cout << "Error: Cannot create/write to file " << filename << endl;
            return 1;
        }
        
        cout << "Enter content to write (empty line to finish):" << endl;
        string line;
        // 只要line不是空白就持续按行输入
        while (getline(cin, line) && !line.empty()) {
            file << line << endl;
        }
        file.close();
        cout << "Content written to file" << endl;
        
    } else { // 模式错误判断
        cout << "Error: Unsupported mode '" << mode << "'" << endl;
        return 1;
    }
    
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;

// 函数-显示帮助信息
void displayHelp(const string& programName) {
    cout << "Usage: " << programName << " [OPTIONS] <filename> [mode]" << endl;
    cout << "A simple file read/write utility @Aerosand" << endl << endl;
    cout << "Arguments:" << endl;
    cout << "  filename          Name of the file to read/write" << endl;
    cout << "  mode              Operation mode: read or write (default: read)" << endl << endl;
    cout << "Options:" << endl;
    cout << "  -h, --help        Display this help message" << endl;
    cout << "  -l                Show line numbers when reading" << endl;
    cout << "  -v, --version     Display version information" << endl;
    cout << "  -a, --append      Use append mode when writing (default)" << endl;
    cout << "  -o, --overwrite   Use overwrite mode when writing" << endl << endl;
    cout << "Examples:" << endl;
    cout << "  " << programName << " data.txt read" << endl;
    cout << "  " << programName << " -l notes.txt" << endl;
    cout << "  " << programName << " -o log.txt write" << endl;
    cout << "  " << programName << " -a data.txt write" << endl;
}

// 函数-显示版本信息
void displayVersion() {
    cout << "Version v1.0 @Aerosand" << endl;
    cout << "This is a ofsp program from Aerosand" << endl;
}

// 结构体-存储配置的命令行参数
struct Config {
    string filename;
    string mode = "read";
    bool showLineNumbers = false;
    bool showHelp = false;
    bool showVersion = false;
    bool appendMode = true;  // 默认为追加模式
    bool overwriteMode = false;
};

// 函数-解析命令行参数
Config parseArguments(int argc, char* argv[]) {
    Config config;
    vector<string> positionalArgs;
    
    // 跳过程序名，遍历其余命令行参数
    for (int i = 1; i < argc; i++) {
        string arg = argv[i];
        
        if (arg == "-h" || arg == "--help") {
            config.showHelp = true;
        } else if (arg == "-l") {
            config.showLineNumbers = true;
        } else if (arg == "-v" || arg == "--version") {
            config.showVersion = true;
        } else if (arg == "-a" || arg == "--append") {
            config.appendMode = true;
            config.overwriteMode = false;
        } else if (arg == "-o" || arg == "--overwrite") {
            config.overwriteMode = true;
            config.appendMode = false;
        } else if (arg[0] == '-') {
            // 未知选项的异常处理
            cerr << "Warning: Unknown option '" << arg << "'" << endl;
            cerr << "Use '" << argv[0] << " --help' for usage information" << endl;
        } else {
            // 除此之外，文件名称和模式
            positionalArgs.push_back(arg);
        }
    }
    
    // 处理文件名称和模式
    if (positionalArgs.size() > 0) {
        config.filename = positionalArgs[0];
    }
    if (positionalArgs.size() > 1) {
        config.mode = positionalArgs[1];
    }
    
    return config;
}

int main(int argc, char* argv[])
{
    // 解析命令行参数
    Config config = parseArguments(argc, argv);
    
    // 如果显示帮助信息
    if (config.showHelp) {
        displayHelp(argv[0]);
        return 0;
    }
    
    // 如果显示版本信息
    if (config.showVersion) {
        displayVersion();
        return 0;
    }
    
    // 空白文件的异常处理
    if (config.filename.empty()) {
        cerr << "Error: No filename specified" << endl;
        cerr << "Use '" << argv[0] << " --help' for usage information" << endl;
        return 1;
    }
    
    // 模式错误的异常处理
    if (config.mode != "read" && config.mode != "write") {
        cerr << "Error: Invalid mode '" << config.mode << "'. Use 'read' or 'write'" << endl;
        return 1;
    }
    
    // 两种模式的实现
    if (config.mode == "read") {
        ifstream file(config.filename);
        if (!file) {
            cerr << "Error: Cannot open file " << config.filename << endl;
            return 1;
        }
        
        string line;
        int lineNumber = 1;
        cout << "File content:" << endl;
        
        while (getline(file, line)) {
            if (config.showLineNumbers) { // 增加行号的显示
                cout << lineNumber << ": " << line << endl;
            } else {
                cout << line << endl;
            }
            lineNumber++;
        }
        file.close();
        
    } else if (config.mode == "write") {
        // 根据选项决定使用追加模式还是覆盖模式
        ios_base::openmode openMode; // C++标准库的类型
        if (config.overwriteMode) {
            openMode = ios::out;  // 标准库中的覆盖模式
        } else {
            openMode = ios::app;  // 标准库中的追加模式（默认）
        }
        
        ofstream file(config.filename, openMode);
        if (!file) { // 文件名称的异常处理
            cerr << "Error: Cannot create/write to file " << config.filename << endl;
            return 1;
        }
        
        cout << "Enter content to write (empty line to finish):" << endl;
        string line;
        while (getline(cin, line) && !line.empty()) {
            file << line << endl;
        }
        file.close();
        
        // 根据模式显示不同的成功消息
        if (config.overwriteMode) {
            cout << "Content written to file (overwritten)" << endl;
        } else {
            cout << "Content appended to file" << endl;
        }
    }
    
    return 0;
}