如何在文件中的特定行上书写？ [英] How to write on a specific line in a file?

问题描述

我想在已经存在的文件上写入一些数据。它是一个包含大约8-10行标题（＃注释），然后成千上行的数据值的文件。我想要的是保持头相同，但添加更新的数据值到文件。很可能在更新后，我有更少的行数据值。

I want to write some data on an already existing file. It is a file that contains about 8-10 lines of header(# comments) and then thousands of lines of data values. What i want is to keep the header same but add the updated data values to the file. It is quite possible that after the update I have less number of lines of data values.

删除标题中最后一个＃注释后的所有内容，然后从那里开始写入新值。这是可能吗？

So basically i want to erase everything after the last # comment in the header and then start writing the new values from there onwards. Is that possible?

以下是一个例子：

strong>原始文件

#Program
#Date
#Hello
0 23 23 54
1 12 4 2
2 253 786 9887
3 3 23 54
4 1 4 4
5 23 6 81

Updated File

#Program
#Date
#Hello
0 2 23 54
2 253 786 9887
5 23 6 81

我编辑的代码是使用 fopen 读取文件， fprintf 它。我更喜欢如果答案是沿着这些线，所以我不必改变这两个。

The code i am editing is using fopen to read the file and fprintf to write to it. I would prefer if the answers are along these lines so that i don't have to change those two.

推荐答案

我想出了打开原始文件，读取和复制头到内存中，如字符串头。然后通过写头覆盖整个文件，然后新数据

The simplest way I came up with is open the Original File, read and copy the header in to memory such as a string header. Then overwrite the whole file by writing the header, then the new data

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