c语言连接数据库备份

在C语言中直接操作数据库并备份通常需要使用数据库API或者特定的数据库驱动程序，如MySQL的libmysqlclient、PostgreSQL的libpq等。这里提供一个简单的示例，我们将使用SQLite数据库作为例子，因为SQLite无需外部库，可以直接在C语言中使用。

首先，确保你安装了SQLite，并包含了相关的头文件`sqlite3.h`：

#include <stdio.h>
#include <sqlite3.h>

// 函数原型声明
int open_database(const char *database_name);
void create_table(sqlite3 *db);
void backup_database(const char *backup_file);

// 示例函数
int open_database(const char *database_name) {
    sqlite3 *db;
    int rc = sqlite3_open(database_name, &db);
    if (rc) {
        fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
        sqlite3_close(db);
        return rc;
    }
    return SQLITE_OK;
}

void create_table(sqlite3 *db) {
    const char *sql_create_table = "CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT)";
    char *err_msg = NULL;
    int result = sqlite3_exec(db, sql_create_table, NULL, NULL, &err_msg);
    if (result != SQLITE_OK) {
        fprintf(stderr, "Error creating table: %s\n", err_msg);
        sqlite3_free(err_msg);
    } else {
        printf("Table created successfully.\n");
    }
}

void backup_database(const char *backup_file) {
    sqlite3_backup *backup;
    int rc = sqlite3_open_v2(backup_file, &backup, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL);
    if (rc == SQLITE_OK) {
        rc = sqlite3_backup_init(backup, "main", "main", NULL); // "main"代表主数据库
        if (rc == SQLITE_OK) {
            rc = sqlite3_backup_step(backup, sqlite3_libversion());
            if (rc == SQLITE_OK) {
                rc = sqlite3_backup_finish(backup);
                if (rc == SQLITE_OK) {
                    printf("Backup completed successfully.\n");
                } else {
                    fprintf(stderr, "Failed to complete backup: %d\n", rc);
                }
            } else {
                fprintf(stderr, "Backup failed: %d\n", rc);
            }
        } else {
            fprintf(stderr, "Backup init failed: %d\n", rc);
        }
        sqlite3_backup_finish(backup);
        sqlite3_close(backup);
    } else {
        fprintf(stderr, "Failed to open backup file: %d\n", rc);
    }
}

int main() {
    if (open_database("test.db") == SQLITE_OK) {
        create_table(NULL); // 假设已成功打开数据库

        // 假设你有定期备份的需求，在这个位置调用backup_database函数备份数据库
        backup_database("backup_test.db");

        sqlite3_close(NULL); // 关闭数据库连接
    }

    return 0;
}