CODEWITHSUNDEEP
rubyfilesearchfile-io
Markus
Markus

Reputation: 161

How to open a file and search for a word?

How can I open a file and search for a word inside it using Ruby?

Upvotes: 14

Views: 15998

Answers (4)

johannes
johannes

Reputation: 7272

All presented solution have a time complexity of O(n). For simplicity I use String#include? to check for the word. This could be done instead with a regular expression in the form string=~ regex.

Read the complete file and search in it.

File.read(filename).include?(word)

If your file is very large, this is not an optimal solution, as you would read the complete file into memory and start searching afterwards. Your memory complexity is O(n)

Read the file line by line and search in each line

File.open(filename) do |f|
  f.any? do |line|
    line.include?(word)
  end
end

If your file is very large, but you know your lines are upperbounded by a constant value, you now have a memory complexity of O(1).

Read chunks of the file and search in it

File.open(filename) do |f|
  tmp= f.read(1024)
  next true if tmp.include?(word)
  until f.eof?
    tmp= tmp[(-1*word.size)..-1] + f.read(1024)
    next true if tmp.include?(word)
  end
  next false
end

In this variant, we are reading equaly sized chunks from the file. So no matter what the conditions of the file are, our memory complexity is O(1)

Upvotes: 32

bmalets
bmalets

Reputation: 3297

Try gem 'search_in_file', it helps you to search word of phrase in specified file or in many files by path

Upvotes: 0

Ben Scheirman
Ben Scheirman

Reputation: 40961

Something like this might help:

def word_exists_in_file
   f = File.open("your_file.txt") #opens the file for reading
   f.each do line
      print line
      if line.match /your_word_to_match/
         return true
      end
   end
   false
end

Upvotes: 3

ennuikiller
ennuikiller

Reputation: 46965

File.readlines(file).each {|l| l.grep(/#{exp_search}/).each {|r| puts file + ' : ' + r}}

Upvotes: 1

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