Question

Text file (or CSV) is:

Data:,,,,,\n  

(but with 100 “,”s)

In C or C++ I would like to open the file and then fill in values between the “,”.
i.e.- Data:,1,2,3,4,\n

I’m guessing that I need some sort of search to find the next comma, insert data, find the next comma insert, etc.

I was looking at memchr() for a buffer and was wondering if there is something similar for a text file?

If you could point me in the right direction, I would appreciate it.

(I don’t mind reading a book to find something out like this either, I just don’t know what book would have this information?)

Thank You.

Answer 1

You can’t actually do that in C… if you open in read/write mode you’ll overwrite characters, not insert them.

http://c-faq.com/stdio/fupdate.html

You need to open the file, read the line into memory, write the new line to a temp file.

After you’re done inserting all the lines, copy the temp file over the original file. I don’t think there’s any other way to do it.