C 语言实例教程 💡

🎯 概述

本章节提供了丰富的 C 语言实例，从基础到进阶，涵盖各种常见的编程场景。每个示例都包含完整的代码、详细的注释和运行结果，帮助你快速掌握 C 语言编程技巧。

📋 目录

基础示例
控制流示例
函数示例
数组和字符串
指针示例
结构体示例
文件操作
动态内存
实用工具
综合项目

1️⃣ 基础示例

示例 1.1：Hello World

#include <stdio.h>

int main(void) {
    printf("Hello, World!\n");
    return 0;
}

输出：

Hello, World!

示例 1.2：变量和数据类型

#include <stdio.h>

int main(void) {
    // 整型
    int age = 25;
    printf("年龄: %d\n", age);
    
    // 浮点型
    float height = 1.75f;
    printf("身高: %.2f 米\n", height);
    
    // 双精度浮点型
    double pi = 3.14159265359;
    printf("圆周率: %.10f\n", pi);
    
    // 字符型
    char grade = 'A';
    printf("等级: %c\n", grade);
    
    // 字符串
    char name[] = "张三";
    printf("姓名: %s\n", name);
    
    return 0;
}

输出：

年龄: 25
身高: 1.75 米
圆周率: 3.1415926536
等级: A
姓名: 张三

示例 1.3：基本运算

#include <stdio.h>

int main(void) {
    int a = 10, b = 3;
    
    printf("a = %d, b = %d\n", a, b);
    printf("加法: %d + %d = %d\n", a, b, a + b);
    printf("减法: %d - %d = %d\n", a, b, a - b);
    printf("乘法: %d * %d = %d\n", a, b, a * b);
    printf("除法: %d / %d = %d\n", a, b, a / b);
    printf("取余: %d %% %d = %d\n", a, b, a % b);
    
    // 浮点数除法
    printf("浮点除法: %.2f / %.2f = %.2f\n", 
           (float)a, (float)b, (float)a / b);
    
    return 0;
}

输出：

a = 10, b = 3
加法: 10 + 3 = 13
减法: 10 - 3 = 7
乘法: 10 * 3 = 30
除法: 10 / 3 = 3
取余: 10 % 3 = 1
浮点除法: 10.00 / 3.00 = 3.33

示例 1.4：输入输出

#include <stdio.h>

int main(void) {
    char name[50];
    int age;
    float height;
    
    printf("请输入您的姓名: ");
    scanf("%s", name);
    
    printf("请输入您的年龄: ");
    scanf("%d", &age);
    
    printf("请输入您的身高(米): ");
    scanf("%f", &height);
    
    printf("\n=== 个人信息 ===\n");
    printf("姓名: %s\n", name);
    printf("年龄: %d 岁\n", age);
    printf("身高: %.2f 米\n", height);
    
    return 0;
}

2️⃣ 控制流示例

示例 2.1：判断奇偶数

#include <stdio.h>

int main(void) {
    int number;
    
    printf("请输入一个整数: ");
    scanf("%d", &number);
    
    if (number % 2 == 0) {
        printf("%d 是偶数\n", number);
    } else {
        printf("%d 是奇数\n", number);
    }
    
    return 0;
}

示例 2.2：计算器

#include <stdio.h>

int main(void) {
    char operator;
    double num1, num2, result;
    
    printf("请输入运算符 (+, -, *, /): ");
    scanf(" %c", &operator);
    
    printf("请输入两个数字: ");
    scanf("%lf %lf", &num1, &num2);
    
    switch (operator) {
        case '+':
            result = num1 + num2;
            printf("%.2f + %.2f = %.2f\n", num1, num2, result);
            break;
        case '-':
            result = num1 - num2;
            printf("%.2f - %.2f = %.2f\n", num1, num2, result);
            break;
        case '*':
            result = num1 * num2;
            printf("%.2f * %.2f = %.2f\n", num1, num2, result);
            break;
        case '/':
            if (num2 != 0) {
                result = num1 / num2;
                printf("%.2f / %.2f = %.2f\n", num1, num2, result);
            } else {
                printf("错误：除数不能为零！\n");
            }
            break;
        default:
            printf("错误：无效的运算符！\n");
    }
    
    return 0;
}

示例 2.3：打印乘法表

#include <stdio.h>

int main(void) {
    int n;
    
    printf("请输入乘法表的大小: ");
    scanf("%d", &n);
    
    printf("\n%d x %d 乘法表:\n\n", n, n);
    
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            printf("%4d", i * j);
        }
        printf("\n");
    }
    
    return 0;
}

输出（n=5）：

5 x 5 乘法表:

   1   2   3   4   5
   2   4   6   8  10
   3   6   9  12  15
   4   8  12  16  20
   5  10  15  20  25

示例 2.4：判断闰年

#include <stdio.h>
#include <stdbool.h>

bool is_leap_year(int year) {
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

int main(void) {
    int year;
    
    printf("请输入年份: ");
    scanf("%d", &year);
    
    if (is_leap_year(year)) {
        printf("%d 年是闰年\n", year);
    } else {
        printf("%d 年不是闰年\n", year);
    }
    
    return 0;
}

示例 2.5：求最大公约数

#include <stdio.h>

// 欧几里得算法
int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}

int main(void) {
    int num1, num2;
    
    printf("请输入两个正整数: ");
    scanf("%d %d", &num1, &num2);
    
    int result = gcd(num1, num2);
    printf("%d 和 %d 的最大公约数是: %d\n", num1, num2, result);
    
    // 最小公倍数
    int lcm = (num1 * num2) / result;
    printf("%d 和 %d 的最小公倍数是: %d\n", num1, num2, lcm);
    
    return 0;
}

3️⃣ 函数示例

示例 3.1：阶乘计算

#include <stdio.h>

// 递归方式
long long factorial_recursive(int n) {
    if (n <= 1) {
        return 1;
    }
    return n * factorial_recursive(n - 1);
}

// 迭代方式
long long factorial_iterative(int n) {
    long long result = 1;
    for (int i = 2; i <= n; i++) {
        result *= i;
    }
    return result;
}

int main(void) {
    int n;
    
    printf("请输入一个正整数: ");
    scanf("%d", &n);
    
    if (n < 0) {
        printf("错误：请输入非负整数！\n");
        return 1;
    }
    
    printf("%d! (递归) = %lld\n", n, factorial_recursive(n));
    printf("%d! (迭代) = %lld\n", n, factorial_iterative(n));
    
    return 0;
}

示例 3.2：斐波那契数列

#include <stdio.h>

// 递归方式（效率低）
int fibonacci_recursive(int n) {
    if (n <= 1) {
        return n;
    }
    return fibonacci_recursive(n - 1) + fibonacci_recursive(n - 2);
}

// 迭代方式（效率高）
int fibonacci_iterative(int n) {
    if (n <= 1) {
        return n;
    }
    
    int prev = 0, curr = 1;
    for (int i = 2; i <= n; i++) {
        int next = prev + curr;
        prev = curr;
        curr = next;
    }
    return curr;
}

int main(void) {
    int n;
    
    printf("请输入要计算的斐波那契数列项数: ");
    scanf("%d", &n);
    
    printf("\n前 %d 项斐波那契数列:\n", n);
    for (int i = 0; i < n; i++) {
        printf("%d ", fibonacci_iterative(i));
    }
    printf("\n");
    
    return 0;
}

示例 3.3：判断素数

#include <stdio.h>
#include <stdbool.h>
#include <math.h>

bool is_prime(int n) {
    if (n <= 1) {
        return false;
    }
    if (n <= 3) {
        return true;
    }
    if (n % 2 == 0 || n % 3 == 0) {
        return false;
    }
    
    // 只需检查到 sqrt(n)
    for (int i = 5; i * i <= n; i += 6) {
        if (n % i == 0 || n % (i + 2) == 0) {
            return false;
        }
    }
    return true;
}

int main(void) {
    int start, end;
    
    printf("请输入范围 (开始 结束): ");
    scanf("%d %d", &start, &end);
    
    printf("\n%d 到 %d 之间的素数:\n", start, end);
    int count = 0;
    for (int i = start; i <= end; i++) {
        if (is_prime(i)) {
            printf("%d ", i);
            count++;
            if (count % 10 == 0) {
                printf("\n");
            }
        }
    }
    printf("\n\n共找到 %d 个素数\n", count);
    
    return 0;
}

示例 3.4：温度转换

#include <stdio.h>

double celsius_to_fahrenheit(double celsius) {
    return celsius * 9.0 / 5.0 + 32.0;
}

double fahrenheit_to_celsius(double fahrenheit) {
    return (fahrenheit - 32.0) * 5.0 / 9.0;
}

double celsius_to_kelvin(double celsius) {
    return celsius + 273.15;
}

double kelvin_to_celsius(double kelvin) {
    return kelvin - 273.15;
}

int main(void) {
    int choice;
    double temp, result;
    
    printf("=== 温度转换器 ===\n");
    printf("1. 摄氏度 → 华氏度\n");
    printf("2. 华氏度 → 摄氏度\n");
    printf("3. 摄氏度 → 开尔文\n");
    printf("4. 开尔文 → 摄氏度\n");
    printf("请选择 (1-4): ");
    scanf("%d", &choice);
    
    printf("请输入温度值: ");
    scanf("%lf", &temp);
    
    switch (choice) {
        case 1:
            result = celsius_to_fahrenheit(temp);
            printf("%.2f°C = %.2f°F\n", temp, result);
            break;
        case 2:
            result = fahrenheit_to_celsius(temp);
            printf("%.2f°F = %.2f°C\n", temp, result);
            break;
        case 3:
            result = celsius_to_kelvin(temp);
            printf("%.2f°C = %.2fK\n", temp, result);
            break;
        case 4:
            result = kelvin_to_celsius(temp);
            printf("%.2fK = %.2f°C\n", temp, result);
            break;
        default:
            printf("无效的选择！\n");
    }
    
    return 0;
}

4️⃣ 数组和字符串

示例 4.1：数组基本操作

#include <stdio.h>

int main(void) {
    int numbers[] = {5, 2, 8, 1, 9, 3, 7, 4, 6};
    int size = sizeof(numbers) / sizeof(numbers[0]);
    
    // 打印数组
    printf("原始数组: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", numbers[i]);
    }
    printf("\n");
    
    // 求和
    int sum = 0;
    for (int i = 0; i < size; i++) {
        sum += numbers[i];
    }
    printf("数组总和: %d\n", sum);
    
    // 求平均值
    double average = (double)sum / size;
    printf("平均值: %.2f\n", average);
    
    // 找最大值和最小值
    int max = numbers[0], min = numbers[0];
    for (int i = 1; i < size; i++) {
        if (numbers[i] > max) max = numbers[i];
        if (numbers[i] < min) min = numbers[i];
    }
    printf("最大值: %d\n", max);
    printf("最小值: %d\n", min);
    
    return 0;
}

示例 4.2：冒泡排序

#include <stdio.h>

void bubble_sort(int arr[], int n) {
    for (int i = 0; i < n - 1; i++) {
        bool swapped = false;
        for (int j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                // 交换
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
                swapped = true;
            }
        }
        // 如果没有交换，说明已经排序完成
        if (!swapped) {
            break;
        }
    }
}

void print_array(int arr[], int n) {
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main(void) {
    int numbers[] = {64, 34, 25, 12, 22, 11, 90};
    int size = sizeof(numbers) / sizeof(numbers[0]);
    
    printf("排序前: ");
    print_array(numbers, size);
    
    bubble_sort(numbers, size);
    
    printf("排序后: ");
    print_array(numbers, size);
    
    return 0;
}

示例 4.3：字符串操作

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

// 字符串长度
int string_length(const char *str) {
    int len = 0;
    while (str[len] != '\0') {
        len++;
    }
    return len;
}

// 字符串反转
void reverse_string(char *str) {
    int len = strlen(str);
    for (int i = 0; i < len / 2; i++) {
        char temp = str[i];
        str[i] = str[len - 1 - i];
        str[len - 1 - i] = temp;
    }
}

// 统计字符
void count_characters(const char *str) {
    int letters = 0, digits = 0, spaces = 0, others = 0;
    
    for (int i = 0; str[i] != '\0'; i++) {
        if (isalpha(str[i])) {
            letters++;
        } else if (isdigit(str[i])) {
            digits++;
        } else if (isspace(str[i])) {
            spaces++;
        } else {
            others++;
        }
    }
    
    printf("字母: %d\n", letters);
    printf("数字: %d\n", digits);
    printf("空格: %d\n", spaces);
    printf("其他: %d\n", others);
}

int main(void) {
    char str1[] = "Hello World";
    char str2[] = "Hello123 World!";
    
    printf("字符串: %s\n", str1);
    printf("长度: %d\n", string_length(str1));
    
    reverse_string(str1);
    printf("反转后: %s\n", str1);
    
    printf("\n字符统计 (%s):\n", str2);
    count_characters(str2);
    
    return 0;
}

示例 4.4：回文判断

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <ctype.h>

bool is_palindrome(const char *str) {
    int left = 0;
    int right = strlen(str) - 1;
    
    while (left < right) {
        // 跳过非字母数字字符
        while (left < right && !isalnum(str[left])) {
            left++;
        }
        while (left < right && !isalnum(str[right])) {
            right--;
        }
        
        // 比较字符（忽略大小写）
        if (tolower(str[left]) != tolower(str[right])) {
            return false;
        }
        
        left++;
        right--;
    }
    
    return true;
}

int main(void) {
    char test_strings[][50] = {
        "level",
        "A man a plan a canal Panama",
        "race car",
        "hello",
        "Was it a car or a cat I saw"
    };
    
    int count = sizeof(test_strings) / sizeof(test_strings[0]);
    
    for (int i = 0; i < count; i++) {
        printf("\"%s\" %s回文\n", 
               test_strings[i],
               is_palindrome(test_strings[i]) ? "是" : "不是");
    }
    
    return 0;
}

示例 4.5：二维数组（矩阵）

#include <stdio.h>

#define ROWS 3
#define COLS 3

void print_matrix(int matrix[][COLS], int rows) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < COLS; j++) {
            printf("%4d", matrix[i][j]);
        }
        printf("\n");
    }
}

void add_matrices(int a[][COLS], int b[][COLS], int result[][COLS], int rows) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < COLS; j++) {
            result[i][j] = a[i][j] + b[i][j];
        }
    }
}

void multiply_matrices(int a[][COLS], int b[][COLS], int result[][COLS], int rows) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < COLS; j++) {
            result[i][j] = 0;
            for (int k = 0; k < COLS; k++) {
                result[i][j] += a[i][k] * b[k][j];
            }
        }
    }
}

int main(void) {
    int matrix1[ROWS][COLS] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    
    int matrix2[ROWS][COLS] = {
        {9, 8, 7},
        {6, 5, 4},
        {3, 2, 1}
    };
    
    int sum[ROWS][COLS];
    int product[ROWS][COLS];
    
    printf("矩阵 A:\n");
    print_matrix(matrix1, ROWS);
    
    printf("\n矩阵 B:\n");
    print_matrix(matrix2, ROWS);
    
    add_matrices(matrix1, matrix2, sum, ROWS);
    printf("\nA + B:\n");
    print_matrix(sum, ROWS);
    
    multiply_matrices(matrix1, matrix2, product, ROWS);
    printf("\nA × B:\n");
    print_matrix(product, ROWS);
    
    return 0;
}

5️⃣ 指针示例

示例 5.1：指针基础

#include <stdio.h>

int main(void) {
    int value = 42;
    int *ptr = &value;
    
    printf("变量值: %d\n", value);
    printf("变量地址: %p\n", (void*)&value);
    printf("指针值（地址）: %p\n", (void*)ptr);
    printf("指针指向的值: %d\n", *ptr);
    
    // 通过指针修改值
    *ptr = 100;
    printf("\n修改后的值: %d\n", value);
    
    return 0;
}

示例 5.2：指针与数组

#include <stdio.h>

int main(void) {
    int numbers[] = {10, 20, 30, 40, 50};
    int *ptr = numbers;  // 数组名就是指向第一个元素的指针
    
    printf("使用数组下标访问:\n");
    for (int i = 0; i < 5; i++) {
        printf("numbers[%d] = %d\n", i, numbers[i]);
    }
    
    printf("\n使用指针访问:\n");
    for (int i = 0; i < 5; i++) {
        printf("*(ptr + %d) = %d\n", i, *(ptr + i));
    }
    
    printf("\n使用指针递增访问:\n");
    ptr = numbers;  // 重置指针
    for (int i = 0; i < 5; i++) {
        printf("*ptr = %d\n", *ptr);
        ptr++;
    }
    
    return 0;
}

示例 5.3：函数指针

#include <stdio.h>

// 定义几个简单的数学函数
int add(int a, int b) { return a + b; }
int subtract(int a, int b) { return a - b; }
int multiply(int a, int b) { return a * b; }
int divide(int a, int b) { return b != 0 ? a / b : 0; }

// 使用函数指针的计算器
int calculate(int a, int b, int (*operation)(int, int)) {
    return operation(a, b);
}

int main(void) {
    int x = 10, y = 5;
    
    printf("%d + %d = %d\n", x, y, calculate(x, y, add));
    printf("%d - %d = %d\n", x, y, calculate(x, y, subtract));
    printf("%d * %d = %d\n", x, y, calculate(x, y, multiply));
    printf("%d / %d = %d\n", x, y, calculate(x, y, divide));
    
    // 函数指针数组
    int (*operations[])(int, int) = {add, subtract, multiply, divide};
    char *symbols[] = {"+", "-", "*", "/"};
    
    printf("\n使用函数指针数组:\n");
    for (int i = 0; i < 4; i++) {
        printf("%d %s %d = %d\n", x, symbols[i], y, operations[i](x, y));
    }
    
    return 0;
}

示例 5.4：指针与字符串

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

// 使用指针复制字符串
void string_copy(char *dest, const char *src) {
    while ((*dest++ = *src++) != '\0');
}

// 使用指针连接字符串
void string_concat(char *dest, const char *src) {
    // 移动到 dest 的末尾
    while (*dest != '\0') {
        dest++;
    }
    // 复制 src 到 dest
    while ((*dest++ = *src++) != '\0');
}

int main(void) {
    char str1[50] = "Hello";
    char str2[50];
    char str3[] = " World";
    
    // 复制字符串
    string_copy(str2, str1);
    printf("复制后: %s\n", str2);
    
    // 连接字符串
    string_concat(str1, str3);
    printf("连接后: %s\n", str1);
    
    // 指针数组（字符串数组）
    char *fruits[] = {"Apple", "Banana", "Orange", "Grape"};
    int count = sizeof(fruits) / sizeof(fruits[0]);
    
    printf("\n水果列表:\n");
    for (int i = 0; i < count; i++) {
        printf("%d. %s\n", i + 1, fruits[i]);
    }
    
    return 0;
}

6️⃣ 结构体示例

示例 6.1：学生管理系统

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

#define MAX_STUDENTS 100

typedef struct {
    int id;
    char name[50];
    int age;
    float score;
} Student;

void print_student(const Student *s) {
    printf("学号: %d\n", s->id);
    printf("姓名: %s\n", s->name);
    printf("年龄: %d\n", s->age);
    printf("成绩: %.2f\n", s->score);
    printf("------------------------\n");
}

float calculate_average(const Student students[], int count) {
    float sum = 0;
    for (int i = 0; i < count; i++) {
        sum += students[i].score;
    }
    return count > 0 ? sum / count : 0;
}

void find_top_student(const Student students[], int count) {
    if (count == 0) return;
    
    int top_index = 0;
    for (int i = 1; i < count; i++) {
        if (students[i].score > students[top_index].score) {
            top_index = i;
        }
    }
    
    printf("成绩最高的学生:\n");
    print_student(&students[top_index]);
}

int main(void) {
    Student students[] = {
        {1001, "张三", 20, 85.5},
        {1002, "李四", 21, 92.0},
        {1003, "王五", 19, 78.5},
        {1004, "赵六", 22, 88.0}
    };
    
    int count = sizeof(students) / sizeof(students[0]);
    
    printf("=== 学生信息 ===\n");
    for (int i = 0; i < count; i++) {
        print_student(&students[i]);
    }
    
    printf("\n平均成绩: %.2f\n\n", calculate_average(students, count));
    
    find_top_student(students, count);
    
    return 0;
}

示例 6.2：图书管理系统

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

#define MAX_BOOKS 100
#define MAX_TITLE 100
#define MAX_AUTHOR 50

typedef struct {
    int id;
    char title[MAX_TITLE];
    char author[MAX_AUTHOR];
    int year;
    bool is_available;
} Book;

typedef struct {
    Book books[MAX_BOOKS];
    int count;
} Library;

void init_library(Library *lib) {
    lib->count = 0;
}

bool add_book(Library *lib, int id, const char *title, 
              const char *author, int year) {
    if (lib->count >= MAX_BOOKS) {
        return false;
    }
    
    Book *book = &lib->books[lib->count];
    book->id = id;
    strncpy(book->title, title, MAX_TITLE - 1);
    strncpy(book->author, author, MAX_AUTHOR - 1);
    book->year = year;
    book->is_available = true;
    
    lib->count++;
    return true;
}

void print_book(const Book *book) {
    printf("ID: %d\n", book->id);
    printf("书名: %s\n", book->title);
    printf("作者: %s\n", book->author);
    printf("出版年份: %d\n", book->year);
    printf("状态: %s\n", book->is_available ? "可借" : "已借出");
    printf("------------------------\n");
}

void list_books(const Library *lib) {
    printf("\n=== 图书列表 ===\n");
    for (int i = 0; i < lib->count; i++) {
        print_book(&lib->books[i]);
    }
}

Book *find_book_by_id(Library *lib, int id) {
    for (int i = 0; i < lib->count; i++) {
        if (lib->books[i].id == id) {
            return &lib->books[i];
        }
    }
    return NULL;
}

bool borrow_book(Library *lib, int id) {
    Book *book = find_book_by_id(lib, id);
    if (book == NULL) {
        printf("未找到该图书！\n");
        return false;
    }
    
    if (!book->is_available) {
        printf("该图书已被借出！\n");
        return false;
    }
    
    book->is_available = false;
    printf("成功借出《%s》\n", book->title);
    return true;
}

bool return_book(Library *lib, int id) {
    Book *book = find_book_by_id(lib, id);
    if (book == NULL) {
        printf("未找到该图书！\n");
        return false;
    }
    
    if (book->is_available) {
        printf("该图书未被借出！\n");
        return false;
    }
    
    book->is_available = true;
    printf("成功归还《%s》\n", book->title);
    return true;
}

int main(void) {
    Library library;
    init_library(&library);
    
    // 添加图书
    add_book(&library, 1, "C程序设计语言", "Brian Kernighan", 1978);
    add_book(&library, 2, "算法导论", "Thomas Cormen", 2009);
    add_book(&library, 3, "深入理解计算机系统", "Randal Bryant", 2015);
    
    // 列出所有图书
    list_books(&library);
    
    // 借书
    printf("\n");
    borrow_book(&library, 1);
    borrow_book(&library, 1);  // 尝试再次借出
    
    // 还书
    printf("\n");
    return_book(&library, 1);
    
    return 0;
}

7️⃣ 文件操作

示例 7.1：文件读写基础

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

int main(void) {
    FILE *fp;
    char content[] = "Hello, File I/O!\n这是第二行。\n";
    
    // 写入文件
    fp = fopen("test.txt", "w");
    if (fp == NULL) {
        perror("无法打开文件");
        return 1;
    }
    
    fprintf(fp, "%s", content);
    fclose(fp);
    printf("文件写入成功！\n");
    
    // 读取文件
    fp = fopen("test.txt", "r");
    if (fp == NULL) {
        perror("无法打开文件");
        return 1;
    }
    
    printf("\n文件内容:\n");
    char buffer[256];
    while (fgets(buffer, sizeof(buffer), fp) != NULL) {
        printf("%s", buffer);
    }
    
    fclose(fp);
    return 0;
}

示例 7.2：学生成绩文件管理

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

typedef struct {
    int id;
    char name[50];
    float score;
} Student;

// 保存学生数据到文件
int save_students(const char *filename, const Student students[], int count) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        return -1;
    }
    
    for (int i = 0; i < count; i++) {
        fprintf(fp, "%d,%s,%.2f\n", 
                students[i].id, 
                students[i].name, 
                students[i].score);
    }
    
    fclose(fp);
    return 0;
}

// 从文件加载学生数据
int load_students(const char *filename, Student students[], int max_count) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        return -1;
    }
    
    int count = 0;
    while (count < max_count && 
           fscanf(fp, "%d,%49[^,],%f\n", 
                  &students[count].id,
                  students[count].name,
                  &students[count].score) == 3) {
        count++;
    }
    
    fclose(fp);
    return count;
}

int main(void) {
    Student students[] = {
        {1001, "张三", 85.5},
        {1002, "李四", 92.0},
        {1003, "王五", 78.5}
    };
    int count = 3;
    
    // 保存到文件
    if (save_students("students.csv", students, count) == 0) {
        printf("学生数据已保存到 students.csv\n");
    }
    
    // 从文件加载
    Student loaded[10];
    int loaded_count = load_students("students.csv", loaded, 10);
    
    if (loaded_count > 0) {
        printf("\n从文件加载了 %d 个学生:\n", loaded_count);
        for (int i = 0; i < loaded_count; i++) {
            printf("%d. %s (学号: %d, 成绩: %.2f)\n",
                   i + 1, loaded[i].name, loaded[i].id, loaded[i].score);
        }
    }
    
    return 0;
}

示例 7.3：文件复制程序

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

int copy_file(const char *source, const char *destination) {
    FILE *src = fopen(source, "rb");
    if (src == NULL) {
        perror("无法打开源文件");
        return -1;
    }
    
    FILE *dest = fopen(destination, "wb");
    if (dest == NULL) {
        perror("无法创建目标文件");
        fclose(src);
        return -1;
    }
    
    char buffer[4096];
    size_t bytes;
    
    while ((bytes = fread(buffer, 1, sizeof(buffer), src)) > 0) {
        if (fwrite(buffer, 1, bytes, dest) != bytes) {
            perror("写入错误");
            fclose(src);
            fclose(dest);
            return -1;
        }
    }
    
    fclose(src);
    fclose(dest);
    return 0;
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("用法: %s <源文件> <目标文件>\n", argv[0]);
        return 1;
    }
    
    printf("正在复制 %s 到 %s...\n", argv[1], argv[2]);
    
    if (copy_file(argv[1], argv[2]) == 0) {
        printf("文件复制成功！\n");
    } else {
        printf("文件复制失败！\n");
        return 1;
    }
    
    return 0;
}

示例 7.4：日志记录系统

#include <stdio.h>
#include <time.h>
#include <stdarg.h>

typedef enum {
    LOG_DEBUG,
    LOG_INFO,
    LOG_WARNING,
    LOG_ERROR
} LogLevel;

const char *log_level_strings[] = {
    "DEBUG",
    "INFO",
    "WARNING",
    "ERROR"
};

void log_message(LogLevel level, const char *format, ...) {
    FILE *fp = fopen("app.log", "a");
    if (fp == NULL) {
        return;
    }
    
    // 获取当前时间
    time_t now = time(NULL);
    struct tm *t = localtime(&now);
    
    // 写入时间戳和日志级别
    fprintf(fp, "[%04d-%02d-%02d %02d:%02d:%02d] [%s] ",
            t->tm_year + 1900, t->tm_mon + 1, t->tm_mday,
            t->tm_hour, t->tm_min, t->tm_sec,
            log_level_strings[level]);
    
    // 写入日志消息
    va_list args;
    va_start(args, format);
    vfprintf(fp, format, args);
    va_end(args);
    
    fprintf(fp, "\n");
    fclose(fp);
}

int main(void) {
    log_message(LOG_INFO, "程序启动");
    log_message(LOG_DEBUG, "调试信息: x = %d, y = %d", 10, 20);
    log_message(LOG_WARNING, "警告: 内存使用率达到 80%%");
    log_message(LOG_ERROR, "错误: 无法连接到数据库");
    log_message(LOG_INFO, "程序结束");
    
    printf("日志已写入 app.log\n");
    return 0;
}

8️⃣ 动态内存

示例 8.1：动态数组

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

int main(void) {
    int n;
    
    printf("请输入数组大小: ");
    scanf("%d", &n);
    
    // 动态分配内存
    int *array = (int *)malloc(n * sizeof(int));
    if (array == NULL) {
        printf("内存分配失败！\n");
        return 1;
    }
    
    // 输入数据
    printf("请输入 %d 个整数:\n", n);
    for (int i = 0; i < n; i++) {
        scanf("%d", &array[i]);
    }
    
    // 计算总和
    int sum = 0;
    for (int i = 0; i < n; i++) {
        sum += array[i];
    }
    
    printf("总和: %d\n", sum);
    printf("平均值: %.2f\n", (double)sum / n);
    
    // 释放内存
    free(array);
    return 0;
}

示例 8.2：动态字符串处理

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

char *string_duplicate(const char *str) {
    if (str == NULL) {
        return NULL;
    }
    
    size_t len = strlen(str);
    char *copy = (char *)malloc(len + 1);
    
    if (copy != NULL) {
        strcpy(copy, str);
    }
    
    return copy;
}

char *string_concat(const char *str1, const char *str2) {
    if (str1 == NULL || str2 == NULL) {
        return NULL;
    }
    
    size_t len1 = strlen(str1);
    size_t len2 = strlen(str2);
    
    char *result = (char *)malloc(len1 + len2 + 1);
    if (result == NULL) {
        return NULL;
    }
    
    strcpy(result, str1);
    strcat(result, str2);
    
    return result;
}

int main(void) {
    const char *original = "Hello";
    
    // 复制字符串
    char *copy = string_duplicate(original);
    if (copy != NULL) {
        printf("原始: %s\n", original);
        printf("复制: %s\n", copy);
        free(copy);
    }
    
    // 连接字符串
    char *combined = string_concat("Hello", " World");
    if (combined != NULL) {
        printf("连接: %s\n", combined);
        free(combined);
    }
    
    return 0;
}

示例 8.3：动态二维数组

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

int **create_matrix(int rows, int cols) {
    int **matrix = (int **)malloc(rows * sizeof(int *));
    if (matrix == NULL) {
        return NULL;
    }
    
    for (int i = 0; i < rows; i++) {
        matrix[i] = (int *)malloc(cols * sizeof(int));
        if (matrix[i] == NULL) {
            // 释放已分配的内存
            for (int j = 0; j < i; j++) {
                free(matrix[j]);
            }
            free(matrix);
            return NULL;
        }
    }
    
    return matrix;
}

void free_matrix(int **matrix, int rows) {
    if (matrix == NULL) {
        return;
    }
    
    for (int i = 0; i < rows; i++) {
        free(matrix[i]);
    }
    free(matrix);
}

void print_matrix(int **matrix, int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%4d", matrix[i][j]);
        }
        printf("\n");
    }
}

int main(void) {
    int rows = 3, cols = 4;
    
    int **matrix = create_matrix(rows, cols);
    if (matrix == NULL) {
        printf("内存分配失败！\n");
        return 1;
    }
    
    // 初始化矩阵
    int value = 1;
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            matrix[i][j] = value++;
        }
    }
    
    printf("矩阵:\n");
    print_matrix(matrix, rows, cols);
    
    free_matrix(matrix, rows);
    return 0;
}

示例 8.4：链表实现

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

typedef struct Node {
    int data;
    struct Node *next;
} Node;

// 创建新节点
Node *create_node(int data) {
    Node *new_node = (Node *)malloc(sizeof(Node));
    if (new_node != NULL) {
        new_node->data = data;
        new_node->next = NULL;
    }
    return new_node;
}

// 在链表头部插入
void insert_front(Node **head, int data) {
    Node *new_node = create_node(data);
    if (new_node == NULL) {
        return;
    }
    
    new_node->next = *head;
    *head = new_node;
}

// 在链表尾部插入
void insert_back(Node **head, int data) {
    Node *new_node = create_node(data);
    if (new_node == NULL) {
        return;
    }
    
    if (*head == NULL) {
        *head = new_node;
        return;
    }
    
    Node *current = *head;
    while (current->next != NULL) {
        current = current->next;
    }
    current->next = new_node;
}

// 删除节点
void delete_node(Node **head, int data) {
    if (*head == NULL) {
        return;
    }
    
    // 如果要删除的是头节点
    if ((*head)->data == data) {
        Node *temp = *head;
        *head = (*head)->next;
        free(temp);
        return;
    }
    
    // 查找要删除的节点
    Node *current = *head;
    while (current->next != NULL && current->next->data != data) {
        current = current->next;
    }
    
    if (current->next != NULL) {
        Node *temp = current->next;
        current->next = current->next->next;
        free(temp);
    }
}

// 打印链表
void print_list(Node *head) {
    Node *current = head;
    while (current != NULL) {
        printf("%d -> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

// 释放链表
void free_list(Node **head) {
    Node *current = *head;
    while (current != NULL) {
        Node *temp = current;
        current = current->next;
        free(temp);
    }
    *head = NULL;
}

int main(void) {
    Node *head = NULL;
    
    // 插入元素
    insert_back(&head, 10);
    insert_back(&head, 20);
    insert_back(&head, 30);
    insert_front(&head, 5);
    
    printf("链表: ");
    print_list(head);
    
    // 删除元素
    delete_node(&head, 20);
    printf("删除 20 后: ");
    print_list(head);
    
    // 释放链表
    free_list(&head);
    return 0;
}

9️⃣ 实用工具

示例 9.1：命令行参数处理

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

void print_usage(const char *program_name) {
    printf("用法: %s [选项] <文件名>\n", program_name);
    printf("选项:\n");
    printf("  -h, --help     显示帮助信息\n");
    printf("  -v, --verbose  详细输出\n");
    printf("  -o <文件>      指定输出文件\n");
}

int main(int argc, char *argv[]) {
    int verbose = 0;
    char *output_file = NULL;
    char *input_file = NULL;
    
    // 解析命令行参数
    for (int i = 1; i < argc; i++) {
        if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
            print_usage(argv[0]);
            return 0;
        } else if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
            verbose = 1;
        } else if (strcmp(argv[i], "-o") == 0) {
            if (i + 1 < argc) {
                output_file = argv[++i];
            } else {
                printf("错误: -o 选项需要参数\n");
                return 1;
            }
        } else {
            input_file = argv[i];
        }
    }
    
    // 检查必需参数
    if (input_file == NULL) {
        printf("错误: 未指定输入文件\n");
        print_usage(argv[0]);
        return 1;
    }
    
    // 处理文件
    if (verbose) {
        printf("输入文件: %s\n", input_file);
        if (output_file != NULL) {
            printf("输出文件: %s\n", output_file);
        }
    }
    
    printf("处理文件: %s\n", input_file);
    
    return 0;
}

示例 9.2：简单的配置文件解析器

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

#define MAX_LINE 256
#define MAX_KEY 50
#define MAX_VALUE 200

typedef struct {
    char key[MAX_KEY];
    char value[MAX_VALUE];
} ConfigItem;

typedef struct {
    ConfigItem items[100];
    int count;
} Config;

void trim(char *str) {
    char *start = str;
    char *end;
    
    // 去除前导空格
    while (*start == ' ' || *start == '\t') {
        start++;
    }
    
    // 去除尾随空格
    end = start + strlen(start) - 1;
    while (end > start && (*end == ' ' || *end == '\t' || *end == '\n')) {
        end--;
    }
    *(end + 1) = '\0';
    
    // 移动字符串
    if (start != str) {
        memmove(str, start, strlen(start) + 1);
    }
}

int load_config(const char *filename, Config *config) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        return -1;
    }
    
    config->count = 0;
    char line[MAX_LINE];
    
    while (fgets(line, sizeof(line), fp) != NULL) {
        // 跳过注释和空行
        if (line[0] == '#' || line[0] == '\n') {
            continue;
        }
        
        // 查找等号
        char *equals = strchr(line, '=');
        if (equals == NULL) {
            continue;
        }
        
        // 分割键和值
        *equals = '\0';
        char *key = line;
        char *value = equals + 1;
        
        trim(key);
        trim(value);
        
        // 保存配置项
        if (config->count < 100) {
            strncpy(config->items[config->count].key, key, MAX_KEY - 1);
            strncpy(config->items[config->count].value, value, MAX_VALUE - 1);
            config->count++;
        }
    }
    
    fclose(fp);
    return 0;
}

const char *get_config_value(const Config *config, const char *key) {
    for (int i = 0; i < config->count; i++) {
        if (strcmp(config->items[i].key, key) == 0) {
            return config->items[i].value;
        }
    }
    return NULL;
}

int main(void) {
    // 创建示例配置文件
    FILE *fp = fopen("config.ini", "w");
    if (fp != NULL) {
        fprintf(fp, "# 配置文件示例\n");
        fprintf(fp, "host = localhost\n");
        fprintf(fp, "port = 8080\n");
        fprintf(fp, "username = admin\n");
        fprintf(fp, "debug = true\n");
        fclose(fp);
    }
    
    // 加载配置
    Config config;
    if (load_config("config.ini", &config) == 0) {
        printf("配置加载成功！\n\n");
        
        // 读取配置值
        printf("host = %s\n", get_config_value(&config, "host"));
        printf("port = %s\n", get_config_value(&config, "port"));
        printf("username = %s\n", get_config_value(&config, "username"));
        printf("debug = %s\n", get_config_value(&config, "debug"));
    }
    
    return 0;
}

示例 9.3：简单的 JSON 解析器（基础版）

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

// 简化的 JSON 解析器，只处理简单的键值对
void parse_json_simple(const char *json) {
    const char *ptr = json;
    
    // 跳过开始的 {
    while (*ptr && *ptr != '{') ptr++;
    if (*ptr) ptr++;
    
    while (*ptr) {
        // 跳过空白字符
        while (*ptr && isspace(*ptr)) ptr++;
        
        // 检查结束
        if (*ptr == '}') break;
        
        // 读取键
        if (*ptr == '"') {
            ptr++;
            const char *key_start = ptr;
            while (*ptr && *ptr != '"') ptr++;
            int key_len = ptr - key_start;
            
            char key[100];
            strncpy(key, key_start, key_len);
            key[key_len] = '\0';
            
            ptr++;  // 跳过结束的 "
            
            // 跳过 :
            while (*ptr && *ptr != ':') ptr++;
            if (*ptr) ptr++;
            
            // 跳过空白
            while (*ptr && isspace(*ptr)) ptr++;
            
            // 读取值
            if (*ptr == '"') {
                // 字符串值
                ptr++;
                const char *value_start = ptr;
                while (*ptr && *ptr != '"') ptr++;
                int value_len = ptr - value_start;
                
                char value[100];
                strncpy(value, value_start, value_len);
                value[value_len] = '\0';
                
                printf("%s: %s\n", key, value);
                ptr++;
            } else if (isdigit(*ptr) || *ptr == '-') {
                // 数字值
                const char *value_start = ptr;
                while (*ptr && (isdigit(*ptr) || *ptr == '.' || *ptr == '-')) {
                    ptr++;
                }
                int value_len = ptr - value_start;
                
                char value[100];
                strncpy(value, value_start, value_len);
                value[value_len] = '\0';
                
                printf("%s: %s\n", key, value);
            }
            
            // 跳过逗号
            while (*ptr && *ptr != ',' && *ptr != '}') ptr++;
            if (*ptr == ',') ptr++;
        }
    }
}

int main(void) {
    const char *json = "{\"name\": \"张三\", \"age\": 25, \"city\": \"北京\"}";
    
    printf("解析 JSON:\n%s\n\n", json);
    printf("结果:\n");
    parse_json_simple(json);
    
    return 0;
}

示例 9.4：进度条显示

#include <stdio.h>
#include <unistd.h>  // for sleep

void print_progress_bar(int current, int total, int width) {
    float percentage = (float)current / total;
    int filled = (int)(percentage * width);
    
    printf("\r[");
    for (int i = 0; i < width; i++) {
        if (i < filled) {
            printf("=");
        } else if (i == filled) {
            printf(">");
        } else {
            printf(" ");
        }
    }
    printf("] %.1f%%", percentage * 100);
    fflush(stdout);
}

int main(void) {
    int total = 100;
    
    printf("处理中...\n");
    for (int i = 0; i <= total; i++) {
        print_progress_bar(i, total, 50);
        usleep(50000);  // 暂停 50 毫秒
    }
    printf("\n完成！\n");
    
    return 0;
}

🚀 综合项目

项目 1：通讯录管理系统

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

#define MAX_CONTACTS 100
#define NAME_LEN 50
#define PHONE_LEN 20
#define EMAIL_LEN 50

typedef struct {
    int id;
    char name[NAME_LEN];
    char phone[PHONE_LEN];
    char email[EMAIL_LEN];
} Contact;

typedef struct {
    Contact contacts[MAX_CONTACTS];
    int count;
} AddressBook;

void init_address_book(AddressBook *book) {
    book->count = 0;
}

int add_contact(AddressBook *book, const char *name, 
                const char *phone, const char *email) {
    if (book->count >= MAX_CONTACTS) {
        return -1;
    }
    
    Contact *contact = &book->contacts[book->count];
    contact->id = book->count + 1;
    strncpy(contact->name, name, NAME_LEN - 1);
    strncpy(contact->phone, phone, PHONE_LEN - 1);
    strncpy(contact->email, email, EMAIL_LEN - 1);
    
    book->count++;
    return contact->id;
}

Contact *find_contact_by_name(AddressBook *book, const char *name) {
    for (int i = 0; i < book->count; i++) {
        if (strcmp(book->contacts[i].name, name) == 0) {
            return &book->contacts[i];
        }
    }
    return NULL;
}

void list_contacts(const AddressBook *book) {
    if (book->count == 0) {
        printf("通讯录为空\n");
        return;
    }
    
    printf("\n%-5s %-20s %-15s %-30s\n", "ID", "姓名", "电话", "邮箱");
    printf("-------------------------------------------------------------------\n");
    
    for (int i = 0; i < book->count; i++) {
        const Contact *c = &book->contacts[i];
        printf("%-5d %-20s %-15s %-30s\n", 
               c->id, c->name, c->phone, c->email);
    }
}

int delete_contact(AddressBook *book, int id) {
    int index = -1;
    for (int i = 0; i < book->count; i++) {
        if (book->contacts[i].id == id) {
            index = i;
            break;
        }
    }
    
    if (index == -1) {
        return -1;
    }
    
    // 移动后面的联系人
    for (int i = index; i < book->count - 1; i++) {
        book->contacts[i] = book->contacts[i + 1];
    }
    
    book->count--;
    return 0;
}

int save_to_file(const AddressBook *book, const char *filename) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        return -1;
    }
    
    for (int i = 0; i < book->count; i++) {
        const Contact *c = &book->contacts[i];
        fprintf(fp, "%d,%s,%s,%s\n", c->id, c->name, c->phone, c->email);
    }
    
    fclose(fp);
    return 0;
}

int load_from_file(AddressBook *book, const char *filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        return -1;
    }
    
    book->count = 0;
    Contact *c;
    
    while (book->count < MAX_CONTACTS) {
        c = &book->contacts[book->count];
        if (fscanf(fp, "%d,%49[^,],%19[^,],%49[^\n]\n",
                   &c->id, c->name, c->phone, c->email) != 4) {
            break;
        }
        book->count++;
    }
    
    fclose(fp);
    return book->count;
}

void print_menu(void) {
    printf("\n=== 通讯录管理系统 ===\n");
    printf("1. 添加联系人\n");
    printf("2. 查找联系人\n");
    printf("3. 显示所有联系人\n");
    printf("4. 删除联系人\n");
    printf("5. 保存到文件\n");
    printf("6. 从文件加载\n");
    printf("0. 退出\n");
    printf("请选择: ");
}

int main(void) {
    AddressBook book;
    init_address_book(&book);
    
    int choice;
    char name[NAME_LEN], phone[PHONE_LEN], email[EMAIL_LEN];
    
    while (1) {
        print_menu();
        scanf("%d", &choice);
        getchar();  // 消耗换行符
        
        switch (choice) {
            case 1:
                printf("姓名: ");
                fgets(name, NAME_LEN, stdin);
                name[strcspn(name, "\n")] = 0;
                
                printf("电话: ");
                fgets(phone, PHONE_LEN, stdin);
                phone[strcspn(phone, "\n")] = 0;
                
                printf("邮箱: ");
                fgets(email, EMAIL_LEN, stdin);
                email[strcspn(email, "\n")] = 0;
                
                if (add_contact(&book, name, phone, email) >= 0) {
                    printf("添加成功！\n");
                } else {
                    printf("通讯录已满！\n");
                }
                break;
                
            case 2:
                printf("请输入姓名: ");
                fgets(name, NAME_LEN, stdin);
                name[strcspn(name, "\n")] = 0;
                
                Contact *found = find_contact_by_name(&book, name);
                if (found != NULL) {
                    printf("\n找到联系人:\n");
                    printf("ID: %d\n", found->id);
                    printf("姓名: %s\n", found->name);
                    printf("电话: %s\n", found->phone);
                    printf("邮箱: %s\n", found->email);
                } else {
                    printf("未找到该联系人\n");
                }
                break;
                
            case 3:
                list_contacts(&book);
                break;
                
            case 4:
                printf("请输入要删除的联系人 ID: ");
                int id;
                scanf("%d", &id);
                
                if (delete_contact(&book, id) == 0) {
                    printf("删除成功！\n");
                } else {
                    printf("未找到该联系人\n");
                }
                break;
                
            case 5:
                if (save_to_file(&book, "contacts.csv") == 0) {
                    printf("保存成功！\n");
                } else {
                    printf("保存失败！\n");
                }
                break;
                
            case 6:
                if (load_from_file(&book, "contacts.csv") >= 0) {
                    printf("加载成功！共 %d 个联系人\n", book.count);
                } else {
                    printf("加载失败！\n");
                }
                break;
                
            case 0:
                printf("再见！\n");
                return 0;
                
            default:
                printf("无效的选择！\n");
        }
    }
    
    return 0;
}

项目 2：简单的文本编辑器

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

#define MAX_LINES 1000
#define MAX_LINE_LENGTH 256

typedef struct {
    char *lines[MAX_LINES];
    int line_count;
} TextBuffer;

void init_buffer(TextBuffer *buffer) {
    buffer->line_count = 0;
    for (int i = 0; i < MAX_LINES; i++) {
        buffer->lines[i] = NULL;
    }
}

void free_buffer(TextBuffer *buffer) {
    for (int i = 0; i < buffer->line_count; i++) {
        free(buffer->lines[i]);
    }
}

int add_line(TextBuffer *buffer, const char *line) {
    if (buffer->line_count >= MAX_LINES) {
        return -1;
    }
    
    buffer->lines[buffer->line_count] = strdup(line);
    if (buffer->lines[buffer->line_count] == NULL) {
        return -1;
    }
    
    buffer->line_count++;
    return 0;
}

void print_buffer(const TextBuffer *buffer) {
    for (int i = 0; i < buffer->line_count; i++) {
        printf("%3d: %s", i + 1, buffer->lines[i]);
    }
}

int load_file(TextBuffer *buffer, const char *filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        return -1;
    }
    
    char line[MAX_LINE_LENGTH];
    while (fgets(line, sizeof(line), fp) != NULL) {
        if (add_line(buffer, line) != 0) {
            break;
        }
    }
    
    fclose(fp);
    return 0;
}

int save_file(const TextBuffer *buffer, const char *filename) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        return -1;
    }
    
    for (int i = 0; i < buffer->line_count; i++) {
        fputs(buffer->lines[i], fp);
    }
    
    fclose(fp);
    return 0;
}

void print_menu(void) {
    printf("\n=== 简单文本编辑器 ===\n");
    printf("1. 显示文本\n");
    printf("2. 添加行\n");
    printf("3. 删除行\n");
    printf("4. 加载文件\n");
    printf("5. 保存文件\n");
    printf("0. 退出\n");
    printf("请选择: ");
}

int main(void) {
    TextBuffer buffer;
    init_buffer(&buffer);
    
    int choice;
    char line[MAX_LINE_LENGTH];
    char filename[100];
    
    while (1) {
        print_menu();
        scanf("%d", &choice);
        getchar();
        
        switch (choice) {
            case 1:
                printf("\n当前文本:\n");
                print_buffer(&buffer);
                break;
                
            case 2:
                printf("输入文本（输入空行结束）:\n");
                while (1) {
                    if (fgets(line, sizeof(line), stdin) == NULL) {
                        break;
                    }
                    if (line[0] == '\n') {
                        break;
                    }
                    add_line(&buffer, line);
                }
                break;
                
            case 3:
                printf("输入要删除的行号: ");
                int line_num;
                scanf("%d", &line_num);
                
                if (line_num > 0 && line_num <= buffer.line_count) {
                    free(buffer.lines[line_num - 1]);
                    for (int i = line_num - 1; i < buffer.line_count - 1; i++) {
                        buffer.lines[i] = buffer.lines[i + 1];
                    }
                    buffer.line_count--;
                    printf("删除成功！\n");
                } else {
                    printf("无效的行号！\n");
                }
                break;
                
            case 4:
                printf("输入文件名: ");
                fgets(filename, sizeof(filename), stdin);
                filename[strcspn(filename, "\n")] = 0;
                
                free_buffer(&buffer);
                init_buffer(&buffer);
                
                if (load_file(&buffer, filename) == 0) {
                    printf("加载成功！共 %d 行\n", buffer.line_count);
                } else {
                    printf("加载失败！\n");
                }
                break;
                
            case 5:
                printf("输入文件名: ");
                fgets(filename, sizeof(filename), stdin);
                filename[strcspn(filename, "\n")] = 0;
                
                if (save_file(&buffer, filename) == 0) {
                    printf("保存成功！\n");
                } else {
                    printf("保存失败！\n");
                }
                break;
                
            case 0:
                free_buffer(&buffer);
                printf("再见！\n");
                return 0;
                
            default:
                printf("无效的选择！\n");
        }
    }
    
    return 0;
}

📚 学习建议

如何使用这些示例

从简单开始：按顺序学习，从基础示例开始
动手实践：亲自编写和运行每个示例
理解原理：不要只是复制代码，要理解每行代码的作用
修改实验：尝试修改示例，观察结果变化
解决问题：遇到错误时，学会调试和解决问题

练习建议

为每个示例添加错误处理
优化代码性能
添加新功能
重构代码使其更清晰
编写测试用例

进阶方向

数据结构：实现栈、队列、树、图等
算法：排序、搜索、动态规划等
系统编程：进程、线程、网络编程
项目实战：开发完整的应用程序

🎓 总结

本章节提供了 50+ 个实用的 C 语言示

C 语言实例教程 💡 ​

🎯 概述 ​

📋 目录 ​

1️⃣ 基础示例 ​

示例 1.1：Hello World ​

示例 1.2：变量和数据类型 ​

示例 1.3：基本运算 ​

示例 1.4：输入输出 ​

2️⃣ 控制流示例 ​

示例 2.1：判断奇偶数 ​

示例 2.2：计算器 ​

示例 2.3：打印乘法表 ​

示例 2.4：判断闰年 ​

示例 2.5：求最大公约数 ​

3️⃣ 函数示例 ​

示例 3.1：阶乘计算 ​

示例 3.2：斐波那契数列 ​

示例 3.3：判断素数 ​

示例 3.4：温度转换 ​

4️⃣ 数组和字符串 ​

示例 4.1：数组基本操作 ​

示例 4.2：冒泡排序 ​

示例 4.3：字符串操作 ​

示例 4.4：回文判断 ​

示例 4.5：二维数组（矩阵） ​

5️⃣ 指针示例 ​

示例 5.1：指针基础 ​

示例 5.2：指针与数组 ​

示例 5.3：函数指针 ​

示例 5.4：指针与字符串 ​

6️⃣ 结构体示例 ​

示例 6.1：学生管理系统 ​

示例 6.2：图书管理系统 ​

7️⃣ 文件操作 ​

示例 7.1：文件读写基础 ​

示例 7.2：学生成绩文件管理 ​

示例 7.3：文件复制程序 ​

示例 7.4：日志记录系统 ​

8️⃣ 动态内存 ​

示例 8.1：动态数组 ​

示例 8.2：动态字符串处理 ​

示例 8.3：动态二维数组 ​

示例 8.4：链表实现 ​

9️⃣ 实用工具 ​

示例 9.1：命令行参数处理 ​

示例 9.2：简单的配置文件解析器 ​

示例 9.3：简单的 JSON 解析器（基础版） ​

示例 9.4：进度条显示 ​

🚀 综合项目 ​

项目 1：通讯录管理系统 ​

项目 2：简单的文本编辑器 ​

📚 学习建议 ​

如何使用这些示例 ​

练习建议 ​

进阶方向 ​

🎓 总结 ​

C 语言实例教程 💡

🎯 概述

📋 目录

1️⃣ 基础示例

示例 1.1：Hello World

示例 1.2：变量和数据类型

示例 1.3：基本运算

示例 1.4：输入输出

2️⃣ 控制流示例

示例 2.1：判断奇偶数

示例 2.2：计算器

示例 2.3：打印乘法表

示例 2.4：判断闰年

示例 2.5：求最大公约数

3️⃣ 函数示例

示例 3.1：阶乘计算

示例 3.2：斐波那契数列

示例 3.3：判断素数

示例 3.4：温度转换

4️⃣ 数组和字符串

示例 4.1：数组基本操作

示例 4.2：冒泡排序

示例 4.3：字符串操作

示例 4.4：回文判断

示例 4.5：二维数组（矩阵）

5️⃣ 指针示例

示例 5.1：指针基础

示例 5.2：指针与数组

示例 5.3：函数指针

示例 5.4：指针与字符串

6️⃣ 结构体示例

示例 6.1：学生管理系统

示例 6.2：图书管理系统

7️⃣ 文件操作

示例 7.1：文件读写基础

示例 7.2：学生成绩文件管理

示例 7.3：文件复制程序

示例 7.4：日志记录系统

8️⃣ 动态内存

示例 8.1：动态数组

示例 8.2：动态字符串处理

示例 8.3：动态二维数组

示例 8.4：链表实现

9️⃣ 实用工具

示例 9.1：命令行参数处理

示例 9.2：简单的配置文件解析器

示例 9.3：简单的 JSON 解析器（基础版）

示例 9.4：进度条显示

🚀 综合项目

项目 1：通讯录管理系统

项目 2：简单的文本编辑器

📚 学习建议

如何使用这些示例

练习建议

进阶方向

🎓 总结