read only given last x lines in txt file [duplicate]

Answer 1

Use Queue<string> to store last X lines and replace the first one with currently read:

int x = 4;   // number of lines you want to get

var buffor = new Queue<string>(x);

var file = new StreamReader("Input.txt");

while (!file.EndOfStream)
{
    string line = file.ReadLine();

    if (buffor.Count >= x)
        buffor.Dequeue();
    buffor.Enqueue(line);
}

string[] lastLines = buffor.ToArray();

string contentOfLastLines = String.Join(Environment.NewLine, lastLines);

Answer 2

What about this

List <string> text = File.ReadLines("file.txt").Reverse().Take(2).ToList()

Answer 3

You can use ReadLines to avoid reading the entire file into memory, like this:

const int neededLines = 5;
var lines = new List<String>();
foreach (var s in File.ReadLines("c:\\myfile.txt")) {
    lines.Add(s);
    if (lines.Count > neededLines) {
        lines.RemoveAt(0);
    }
}

Once the for loop is finished, the lines list contains up to the last neededLines of text from the file. Of course if the file does not contain as many lines as required, fewer lines will be placed in the lines list.

Answer 4

Since reading a file is done linearly, usually line-by-line. Simply read line-by-line and remember last two lines (you can use queue or something if you want... or just two string variables). When you get to EOF, you'll have your last two lines.

Answer 5

Read the lines into an array, then extract the last two:

string[] lines = File.ReadAllLines();
string last2 = lines[lines.Count-2] + Environment.NewLine + lines[lines.Count-1];

Assuming your file is reasonably small, it's easier to just read the whole thing and throw away what you don't need.

Answer 6

You want to read the file backwards using ReverseLineReader:

How to read a text file reversely with iterator in C#

Then run .Take(2) on it. var lines = new ReverseLineReader(filename); var last = lines.Take(2);

OR

Use a System.IO.StreamReader.

string line1, line2;

using(StreamReader reader = new StreamReader("myFile.txt")) {
    line1 = reader.ReadLine();
    line2 = reader.ReadLine();
}