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    <pre><code>file.lines.drop(500).take(100) # will get you lines 501-600 </code></pre> <p>Generally, you can't avoid reading file from the start until the line you are interested in, as each line can be of different length. The one thing you can avoid, though, is loading whole file into a big array. Just read line by line, counting, and discard them until you reach what you look for. Pretty much like your own example. You can just make it more Rubyish.</p> <p>PS. the Tin Man's comment made me do some experimenting. While I didn't find any reason why would <code>drop</code> load whole file, there is indeed a problem: <code>drop</code> <em>returns</em> the rest of the file in an array. Here's a way this could be avoided:</p> <pre><code>file.lines.select.with_index{|l,i| (501..600) === i} </code></pre> <p>PS2: Doh, above code, while not making a huge array, iterates through the whole file, even the lines below 600. :( Here's a third version:</p> <pre><code>enum = file.lines 500.times{enum.next} # skip 500 enum.take(100) # take the next 100 </code></pre> <p>or, if you prefer FP:</p> <pre><code>file.lines.tap{|enum| 500.times{enum.next}}.take(100) </code></pre> <p>Anyway, the good point of this monologue is that you can learn multiple ways to iterate a file. ;)</p>
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    1. POFastest way to skip lines while parsing files in Ruby?
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    1. USMladen Jablanović
    1. USMladen Jablanović
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    1. COThat does look more Rubyish! I had only really thought about that after I posted the question - the fact that "lines" aren't really set by anything other than "the space between 'new line' characters" (or rather before and after). Which would mean that They all have to be parsed for that character anyway. I guess if I had a general idea of the space preceding the required lines, in bits/bytes/whatever, I could jump that area and then start parsing line by line, but for the time I'll accept that it works pretty well as is. Or as will be with a nicer looking line like your own! Thank you.
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      1. USDRobinson
    2. COActually, you _could_ make use of `seek` if the lines contained some kind of information related to their position in file (such as line numbers or sorted timestamps). Then you could pull some variant of binary search. You can open another question if that would help in your particular case.
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      1. USMladen Jablanović
    3. COThis does lead to some scalability concerns though. If the file has several million lines, its going to be read into memory completely before you can `drop`. That could be slow and make the machine be unresponsive as its loading the data, or fill all available memory if the lines are long, causing paging. For a safer approach with a text file you're better off reading them a line at a time, skipping them until you reach the ones you want, then capture only the needed lines.
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      1. USthe Tin Man
 

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