I have a 200kb file, what I use in multiple pages, but on each page I need only 1-2 lines of that file so how I can read only these lines what I need if I know the line number?
For example if I need only the 10th line, I don`t want to load in memory all the lines, just the 10th line.
Sorry for my bad english!
Unless you know the offset of the line, you will need to read every line up to that point. You can just throw away the old lines (that you don't want) by looping through the file with something like fgets(). (EDIT: Rather than fgets(), I would suggest @Gordon's solution)
Possibly a better solution would be to use a database, as the database engine will do the grunt work of storing the strings and allow you to (very efficiently) get a certain "line" (It wouldn't be a line but a record with an numeric ID, however it amounts to the same thing) without having to read the records before it.