C++ 文件概念与文本文件操作 完全指南

#include <iostream>
#include <fstream>

int main() {
    std::ofstream fout("hello.txt");
    if (!fout.is_open()) {
        std::cout << "创建失败！" << std::endl;
        return 1;
    }
    fout << "Hello, C++ File!" << std::endl;
    fout.close();
    std::cout << "文件写入成功！" << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

int main() {
    std::ifstream fin("data.txt");
    if (!fin.is_open()) {
        std::cout << "打开失败！" << std::endl;
        return 1;
    }
    std::string line;
    while (std::getline(fin, line)) {
        std::cout << line << std::endl;
    }
    fin.close();
    return 0;
}

#include <iostream>
#include <fstream>
#include <algorithm>

int main() {
    int scores[5];
    std::ofstream fout("score.txt");
    for (int i = 0; i < 5; i++) {
        std::cin >> scores[i];
        fout << scores[i] << std::endl;
    }
    fout.close();

    int sum = 0, mx = scores[0], mn = scores[0];
    std::ifstream fin("score.txt");
    int s;
    while (fin >> s) {
        sum += s;
        mx = std::max(mx, s);
        mn = std::min(mn, s);
    }
    fin.close();

    std::ofstream fout2("result.txt");
    fout2 << "平均分: " << sum / 5 << std::endl;
    fout2 << "最高分: " << mx << std::endl;
    fout2 << "最低分: " << mn << std::endl;
    fout2.close();
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ofstream fout("words.txt");
    std::string w;
    while (std::cin >> w && w != "end") {
        fout << w << std::endl;
    }
    fout.close();
    std::cout << "写入完成！" << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>

int main() {
    std::ifstream fin("text.txt");
    int count = 0;
    char ch;
    while (fin.get(ch)) count++;
    fin.close();
    std::cout << "字符总数: " << count << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ofstream fout("test.txt");
    fout << "A";  // ios::out 默认清空
    fout.close();

    std::ofstream fout2("test.txt", std::ios::app);
    fout2 << "B";  // 追加
    fout2.close();

    std::ifstream fin("test.txt");
    std::string s;
    while (fin >> s) std::cout << s;
    fin.close();
    std::cout << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>

struct Student {
    char name[50];  // 定长字符数组：可安全二进制读写
    int score;
};

int main() {
    Student students[3];
    for (int i = 0; i < 3; i++) {
        std::cin >> students[i].name >> students[i].score;
    }

    std::ofstream fout("students.dat", std::ios::binary);
    for (int i = 0; i < 3; i++) {
        fout.write((char*)&students[i], sizeof(Student));
    }
    fout.close();

    Student s;
    std::ifstream fin("students.dat", std::ios::binary);
    while (fin.read((char*)&s, sizeof(Student))) {
        std::cout << s.name << ": " << s.score << std::endl;
    }
    fin.close();
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <map>

int main() {
    std::ifstream fin("article.txt");
    std::map<std::string, int> freq;
    std::string w;
    while (fin >> w) freq[w]++;
    fin.close();

    std::string max_word;
    int max_count = 0;
    for (auto &p : freq) {
        if (p.second > max_count) {
            max_count = p.second;
            max_word = p.first;
        }
    }
    std::cout << max_word << ": " << max_count << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>

int main() {
    std::ifstream fin("source.txt");
    if (!fin.is_open()) {
        std::cout << "源文件不存在！" << std::endl;
        return 1;
    }

    std::ofstream fout("copy.txt");
    char ch;
    int count = 0;
    while (fin.get(ch)) {
        fout.put(ch);
        count++;
    }
    fin.close();
    fout.close();

    std::cout << "拷贝完成，共拷贝 " << count << " 字节" << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

int main() {
    std::ifstream fin("data.txt");
    int lines = 0, words = 0, chars = 0;
    std::string line, w;
    while (std::getline(fin, line)) {
        lines++;
        for (char c : line) {
            if (c != ' ') chars++;
        }
        std::istringstream iss(line);
        while (iss >> w) words++;
    }
    fin.close();
    std::cout << "行数: " << lines << std::endl;
    std::cout << "单词数: " << words << std::endl;
    std::cout << "非空格字符数: " << chars << std::endl;
    return 0;
}

#include <iostream>
#include <fstream>
#include <algorithm>

struct Student {
    int id;
    char name[50];  // 定长字符数组：可安全二进制读写
    int score;
};

int main() {
    int n;
    std::cin >> n;
    Student *arr = new Student[n];
    for (int i = 0; i < n; i++) {
        std::cin >> arr[i].id >> arr[i].name >> arr[i].score;
    }

    std::ofstream fout("students.dat", std::ios::binary);
    for (int i = 0; i < n; i++) {
        fout.write((char*)&arr[i], sizeof(Student));
    }
    fout.close();

    std::sort(arr, arr + n, [](const Student& a, const Student& b) {
        return a.score > b.score;
    });

    std::ofstream fout2("sorted.dat", std::ios::binary);
    for (int i = 0; i < n; i++) {
        fout2.write((char*)&arr[i], sizeof(Student));
    }
    fout2.close();

    for (int i = 0; i < n; i++) {
        std::cout << arr[i].name << ": " << arr[i].score << std::endl;
    }
    delete[] arr;
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ifstream fin("input.txt");
    std::string content;
    char ch;
    while (fin.get(ch)) content += ch;
    fin.close();

    std::reverse(content.begin(), content.end());

    std::ofstream fout("output.txt");
    fout << content;
    fout.close();
    return 0;
}

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cstring>

struct Contact {
    char name[50], phone[20], email[50];  // 定长字符数组：可安全二进制读写
};

int main() {
    std::vector<Contact> contacts;
    std::string name;
    while (std::cin >> name && name != "end") {
        Contact c;
        strcpy(c.name, name.c_str());
        std::cin >> c.phone >> c.email;
        contacts.push_back(c);
    }

    std::ofstream fout("contacts.dat", std::ios::binary);
    for (auto &c : contacts) {
        fout.write((char*)&c, sizeof(Contact));
    }
    fout.close();

    std::sort(contacts.begin(), contacts.end(),
        [](const Contact& a, const Contact& b) {
            return strcmp(a.name, b.name) < 0;
        });

    for (auto &c : contacts) {
        std::cout << c.name << " " << c.phone << " " << c.email << std::endl;
    }
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <map>

int main() {
    std::ifstream fin("server.log");
    int total = 0, err404 = 0, err500 = 0;
    std::map<std::string, int> op_count;
    std::string ts, op, code;

    while (fin >> ts >> op >> code) {
        total++;
        op_count[op]++;
        if (code == "404") err404++;
        if (code == "500") err500++;
    }
    fin.close();

    std::ofstream fout("report.txt");
    fout << "总请求数: " << total << std::endl;
    for (auto &p : op_count) {
        fout << p.first << ": " << p.second << std::endl;
    }
    fout << "404错误: " << err404 << std::endl;
    fout << "500错误: " << err500 << std::endl;
    fout.close();
    return 0;
}