如何重写文件的第一行? [英] How rewrite first line of a file ?

问题描述

我如何重写一行的第一行而又不复制文件并重写它.我正在使用顺序写入，例如我的文件包含数据

How can i rewrite the first line of a line with out making a copy of file and rewriting it. I am using sequential writing for example my file contains data

hey<br />
how are you everyone at codeproject??

我想将其重写为

and i want to rewrite it as

hello!!<br />
how are you everyone at codeproject??

我尝试过此代码

i tried this code

ofstream fout2("res.dat",ios::app);
	fout2.seekp(0, ios::beg);
	fout2<<str;
	fout2.close();

但是它将str写入文件的末尾:(

有任何建议吗?

but it write str to the end of the file :(

Any suggestions ?

推荐答案

您不能这样做.
您必须将文件内容复制到内存缓冲区，然后按照您所描述的方式重写文件.
:-)

You cannot do that.
You have to copy file content to a memory buffer and then rewrite the file the way you depicted.
:-)

如果您的第一行始终是固定大小，则可以这样做.否则，您必须使用修改后的数据重写新文件.

If your first line is always of a fixed size, you can do that. Else, you have to rewrite a new file with the modified data.

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