real 1m56.190s
user 0m1.400s
sys 0m0.940s


Using Ruby to write a script, which I named Grope, I made the search process 450 times faster, reducing an operation that took more than a minute to taking a blink of an eye…

user@localhost$ time grope 'hello'
templates/festival/06/temp.tpl: 1
hello...

real 0m0.181s
user 0m0.100s
sys 0m0.070s


The first version works from the command line and makes use of concatenating a file and piping it to a ruby command which then diverts the output in to a file, a one liner:
cat input.csv | ruby -pe 'gsub( /\t+/, "," )' > output.csv

This can be further enhanced by using the in-place-edit switch of the Ruby interpreter, editing the input.csv file and leaving a pristine copy with .bak extension.
ruby -i.bak -pe 'gsub( /\t+/, "," )' input.csv


The final version is what you might put in to a Ruby file. Although the input and output files are hard-coded, it would be trivial to allow them to be specified on the command line.

#!/usr/bin/env ruby

# Initialise a new file object that is writable
file = File.new( "output.csv", "w" )

# Open the existing tab delimited file and read each line
File.open( "input.csv", "r" ).each do |line|
  # Perform a global substitution of tabs with commas and
  # put that in the new file
  file.puts line.gsub( /\t+/, "," )
end

# Tidy up by closing the newly written output file.
file.close