读写文件操作

C语言方法

参考博客：函数基本介绍：

https://www.cnblogs.com/lidabo/p/6813354.html

自己写了个demo测试一下fopen、feek、fwrite、fread函数的使用，代码如下：

    void OperationFile_C() {FILE* fp = NULL;fp = fopen("D:\\test01.txt", "w");if (NULL == fp) {cout << "打开文件失败" << endl;}char ByteToWrite[20] = "\x0a\x0A\x0a\x0A";int num = fwrite(ByteToWrite, 1, strlen(ByteToWrite), fp);cout << "写入的字节数：" << num << endl;int nRet = fclose(fp);fp = NULL;fp = fopen("D:\\test01.txt", "r");if (NULL == fp) {cout << "打开文件失败" << endl;}fpos_t pos = 0;nRet = fseek(fp,0,SEEK_END);fgetpos(fp, &pos);//通过此方式可以获取出来文件的大小nRet = fseek(fp, 0, SEEK_SET);cout << "文件实际包含的字节数：" << pos << endl;char ByteToRead[40] = { 0 };num = fread(ByteToRead, 1, pos, fp);cout << "读取到的字节数：" << num << endl;nRet = fclose(fp);fp = NULL;fp = fopen("D:\\test01.txt", "rb");if (NULL == fp) {cout << "打开文件失败" << endl;}pos = 0;nRet = fseek(fp, 0, SEEK_END);fgetpos(fp, &pos);//通过此方式可以获取出来文件的大小nRet = fseek(fp, 0, SEEK_SET);cout << "文件实际包含的字节数：" << pos << endl;memset(ByteToRead, 0, sizeof(ByteToRead));num = fread(ByteToRead, 1, pos, fp);cout << "读取到的字节数：" << num << endl;nRet = fclose(fp);fp = NULL;cout << "=============================" << endl;fp = fopen("D:\\test02.txt", "wb");num = fwrite(ByteToWrite, 1, strlen(ByteToWrite), fp);cout << "写入的字节数：" << num << endl;fclose(fp);memset(ByteToRead, 0, sizeof(ByteToRead));fp = fopen("D:\\test02.txt", "rb");pos = 0;fseek(fp, 0, SEEK_END);fgetpos(fp, &pos);fseek(fp, 0, SEEK_SET);cout << "文件实际包含的字节数：" << pos << endl;num = fread(ByteToRead, 1, pos, fp);cout << "读到的字节数：" << num << endl;fclose(fp);}

运行结果如下图所示：

使用notepad++来观察两文件的十六进制显示：

观察发现以不带"b"的方式访问文件会写入0x0d，也不会读出0x0d。这里解释一下，如果不带"b"则以文本方式访问文件即：
“w”=“wt”，“r”=“rt”。而windows下对文本中的’\n’，会处理成"\r\n"，即0x0d0a，相关文章可参考：

https://blog.csdn.net/qq_40395278/article/details/81199281