Quickly replace first line of large file
c#, replace
Solution
If you can guarantee that `fixedLine` is the same length (or less) as `line`, you can update the files in-place instead of copying them.
If not, you can possibly get a little performance improvement by accessing the `.BaseStream` of your `StreamReader` and `StreamWriter` and doing big block copies (using, say, a 32K byte buffer) to do the copying, which will at least eliminate the time spent checking every character to see if it's an end-of-line character as happens now with `reader.ReadLine()`.
Problem
I have many large csv files (1-10 gb each) which I'm importing into databases. For each file, I need to replace the 1st line so I can format the headers to be the column names. My current solution is: ``` using (var reader = new StreamReader(file)) { using (var writer = new StreamWriter(fixed)) { var line = reader.ReadLine(); var fixedLine = parseHeaders(line); writer.WriteLine(fixedLine); while ((line = reader.ReadLine()) != null) writer.WriteLine(line); } } ``` What is a quicker way to only replace line 1 without iterating through every other line of these huge files?