在C中修改二进制文件中的某些字节 [英] Modify some bytes in a binary file in C

问题描述

是否可以更改二进制文件中单个字节的值？我知道，如果您以 r + b 模式打开文件，则光标将位于现有文件的开头，并且您在该文件中写入的所有内容都会覆盖现有内容

Is there any way to change the value of a single byte in a binary file? I know that if you open the file in r+b mode, the cursor is positioned at the beginning of the existing file and anything you write in that file will overwrite the existing content.

但是我只想更改文件中的1个字节。我想您可以复制不应修改的文件内容，并在正确的位置插入所需的值，但是我想知道是否还有其他方法。

But I want to change only 1 byte, for instance, in a file. I guess you could copy the content of the file that should not be modified and insert the desired value at the right place, but I wonder if there is any other way.

我要实现的示例：
将第3个字节更改为67

An example of what I would like to achieve: Change 3rd byte to 67

初始文件：

00 2F 71 73 76 95

写入后的文件内容：

00 2F 67 73 76 95

推荐答案

使用 fseek 移动到文件中的位置：

Use fseek to move to a position in a file:

FILE *f = fopen( "file.name", "r+b" );
fseek( f, 3, SEEK_SET ); // move to offest 3 from begin of file
unsigned char newByte = 0x67;
fwrite( &newByte, sizeof( newByte ), 1, f );
fclose( f );

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