Best practices with STDIN in Ruby? [closed]

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Following are some things I found in my collection of obscure Ruby.

So, in Ruby, a simple no-bells implementation of the Unix command cat would be:

#!/usr/bin/env ruby
puts ARGF.read

ARGF is your friend when it comes to input; it is a virtual file that gets all input from named files or all from STDIN.

ARGF.each_with_index do |line, idx|
    print ARGF.filename, ":", idx, ";", line
end

# print all the lines in every file passed via command line that contains login
ARGF.each do |line|
    puts line if line =~ /login/
end

Thank goodness we didn’t get the diamond operator in Ruby, but we did get ARGF as a replacement. Though obscure, it actually turns out to be useful. Consider this program, which prepends copyright headers in-place (thanks to another Perlism, -i) to every file mentioned on the command-line:

#!/usr/bin/env ruby -i

Header = DATA.read

ARGF.each_line do |e|
  puts Header if ARGF.pos - e.length == 0
  puts e
end

__END__
#--
# Copyright (C) 2007 Fancypants, Inc.
#++

Credit to:

  • https://web.archive.org/web/20080725055721/http://www.oreillynet.com/ruby/blog/2007/04/trivial_scripting_with_ruby.html#comment-565558
  • http://blog.nicksieger.com/articles/2007/10/06/obscure-and-ugly-perlisms-in-ruby

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