文件操作示例

#include <stdio.h>

int copy_file(const char *src, const char *dst)
{
    FILE *in = fopen(src, "rb");
    if (in == NULL) return -1;
    
    FILE *out = fopen(dst, "wb");
    if (out == NULL) {
        fclose(in);
        return -1;
    }
    
    char buffer[4096];
    size_t n;
    while ((n = fread(buffer, 1, sizeof(buffer), in)) > 0) {
        fwrite(buffer, 1, n, out);
    }
    
    fclose(in);
    fclose(out);
    return 0;
}

void process_lines(const char *filename)
{
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) return;
    
    char line[256];
    int line_num = 0;
    
    while (fgets(line, sizeof(line), fp) != NULL) {
        line_num++;
        /* 去掉换行符 */
        line[strcspn(line, "\n")] = '\0';
        
        printf("Line %d: %s\n", line_num, line);
    }
    
    fclose(fp);
}

/* 简单 key=value 格式 */
void read_config(const char *filename)
{
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) return;
    
    char line[256];
    while (fgets(line, sizeof(line), fp) != NULL) {
        char key[128], value[128];
        if (sscanf(line, "%127s = %127s", key, value) == 2) {
            printf("%s = %s\n", key, value);
        }
    }
    
    fclose(fp);
}

struct Record {
    int id;
    char name[32];
    double score;
};

void save_records(const char *filename, struct Record *records, int n)
{
    FILE *fp = fopen(filename, "wb");
    if (fp == NULL) return;
    
    /* 写入数量 */
    fwrite(&n, sizeof(int), 1, fp);
    
    /* 写入记录 */
    fwrite(records, sizeof(struct Record), n, fp);
    
    fclose(fp);
}

int load_records(const char *filename, struct Record *records, int max_n)
{
    FILE *fp = fopen(filename, "rb");
    if (fp == NULL) return -1;
    
    int n;
    fread(&n, sizeof(int), 1, fp);
    
    if (n > max_n) n = max_n;
    fread(records, sizeof(struct Record), n, fp);
    
    fclose(fp);
    return n;
}