Extracting various lines from file using ruby

Question

I have a number of text files, need to extract the first instance of some single lines, some consecutive lines and some text between lines:

Document 1

Title of the document
(TOD)

Release 3
Version 2

Authors

Thomas E. Thomas, John L. John,
Fred A. Fred, Sandra K. Sandra

Company A Address

More Authors

Page 3

From this example I need "Title of the Document (TOD)", 3, 2, and all the text between Authors and Page 3, not inclusive. I'm slowly learning so I have some code snippets, but they don't go far enough. I can get a match but need the first instance, and the instance and next line:

File.open("sample.txt").each do |line|
    if line[/Document/]
        puts line

I've tried to get intervening text but it's not quite right:

File.open("sample.txt").each do |line|
while gets
  print if [/Authors/../Page/]
end

If you feel this is too much help to ask for I'd appreciate hints/pointers.

Couldn't you just output lines until you hit the "Page 3" line? — Dave Newton
– Dave Newton, Commented Nov 3, 2011 at 1:41
You need to use a state-based approach. Keep track of what 'state' you're in, and for each line use a case statement to decide what to look for and what to do with what you find, and to change the state variable to a new value (probably a symbol) when it sees something else. — Phrogz
– Phrogz, Commented Nov 3, 2011 at 4:54

Dty · Accepted Answer · 2011-11-03 07:59:31Z

4

Rather than read the file line by line I think it would be easier to read in the whole thing then search through it with regex. Something like:

File.open("sample.txt","r") do |f|
  text = f.read

  # everything between Document and Authors
  m1 = text.match(/Document(.*)Authors/m)

  # everything between Authors and Page
  m2 = text.match(/Authors(.*)Page/m)
end

edited Nov 3, 2011 at 7:59

answered Nov 3, 2011 at 4:44

Dty

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1 Comment

Michael Kohl Over a year ago

You'll want to use the m regex modifier for this (it makes . match newline characters). w is not a valid regex option in Ruby.

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