Reading the last n lines of a file

Question

So like the title of this post says how can i read the last n lines of a file and store them in a List?

Keep it in mind that:

the file is big (somewhere between 5 MB and 10 MB)
the file may or may not be locked by another thread
it is accessed by another thread (a new line is added to file when process finished)

Thank you.

This isn't a "write it for me" forum. You write some code, we help you fixing it, or you have a simple question, we respond to the question — xanatos, Apr 19 '15 at 08:39
It seems to be you want to write a "tail" program. Try googling for tail c# file — xanatos, Apr 19 '15 at 08:41
You may want to think about synchronization between the the threads. Otherwise the reader may conceivably see an incomplete last line and will in general stop reading at unpredictable spots (which may or may not be a problem). — Peter - Reinstate Monica, Apr 19 '15 at 09:34
I marked the question as duplicate. use Jon's `ReverseLineReader` and use `Take(n)` to take last n lines. — Sriram Sakthivel, Apr 19 '15 at 09:47

Eliad · Accepted Answer · 2015-04-19T09:35:51.203

1

you can use this code:

            List<string> Temp = new List<string>();
            int SkipLinesNum = 8;
            var GetAllFileToVar = File.ReadLines(@"C:\Sahbak\LinesToList.txt").Skip(SkipLinesNum);
            for (int n = 0; n < GetAllFileToVar.Count(); n++)
            {
                Temp.Add(GetAllFileToVar.ElementAt(0));
            }

now you have List of string called "Temp" that contains all lines from n=8. you can edit you "n" number any time, and also get it from the user.

this is the most efficient method, where you do not load all file to memory.

edited Apr 19 '15 at 09:35

answered Apr 19 '15 at 09:06

Eliad

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The OP said file sizes would be 5 to 10 MB. Doesnt seem very efficient to load all that stuff into memory... – Udontknow Apr 19 '15 at 09:16
@Udontknow Doesn't look too inefficient either, even not on your phone ;-). – Peter - Reinstate Monica Apr 19 '15 at 09:31
1

Well, at least it´s working, but i would rather have my programs not wasting resources. If each and every program would work like that, your phone would not be fun to use... ;-) – Udontknow Apr 19 '15 at 09:40
This works if you know how many rows you need to skip. But the file is in continuously change so... thanks. – Cristian Szpisjak Apr 19 '15 at 10:37
you can change the "n" number anytime. – Eliad Apr 19 '15 at 12:33

Reading the last n lines of a file

1 Answers1