How do I quickly search the end of a huge text file?

[Brian Green]

I am trying to create a ruby script that will search a maya ascii file
for specific text. The problem I'm running into is that it's running to
slow for the system at work. I know that all the information I need is
in the last 5% of the text file - but I haven't been able to figure out
a way to either jump to near the end, and then start search through
lines or even better iterating backwards through the file till I find
what I'm looking for... here is the code I'm currently using - which
works but slowly - any suggestions for how to speed this up would be
greatly appreciated!

require "FileUtils"
require "ftools"

def FindRenderLayers (root)
layersFile = []
dirLocation = root.gsub(/(\\)$/, '')
list = Dir.entries(dirLocation)

list.each do |file|
if file =~ /\.ma$/
fileName = root + file
layersFile.push file
File.open(fileName) do |file|
while line = file.gets
if line =~ /connectAttr
(\"renderLayerManager.rlmi\[[0-9]\]\")/
if $1 != "defaultRenderLayer"
editedLine = "-" + $1
layersFile.push editedLine
end
end
end
end
end
end
return layersFile
end

root = "C:\\Users\\Brian\\Documents\\Ruby\\"
puts FindRenderLayers(root)

 

[Victor H. Goff III]

[Note: parts of this message were removed to make it a legal post.]

IO::SEEK_END at Ruby-Doc may be the ticket...
http://www.ruby-doc.org/core/classes/IO.html#M002305

 

[Brian Green]

Thank you very much!! That's exactly what I was looking for!

I just added

file.seek(-2000,IO::SEEK_END)

right after the line

fileSize = File.size(fileName)

and it worked perfectly! It's running about 18x faster - which is a huge
improvement - I think the guys at work will be satisifed with it's speed
now!

Thanks again Lex!!

Here is an usage example :

begin
file = File.open(ARGV[0])
rescue
puts "file does not exist or is not a file\n"
end

file.seek(-25,IO::SEEK_END)
puts file.readlines

The code will read the rest of the files from that location . Try it on
a file and see .

I meant the rest of the lines . Sorry .