Ruby one-liners (file manipulation)

Jul 20
2007
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# number each line of a file
ruby -ne 'puts "#{$.}\t#{$_}"' file.txt
 
# print all non-blank lines
ruby -pe '$_.chomp.empty? and next' file.txt
 
# number and print all non-blank lines
ruby -ne '$_.chomp.empty? or print $.,"\t", $_' file.txt
 
# number and print each blank line
ruby -ne 'puts $. if $_.chomp.empty?' file.txt
 
# reverse order of lines (`tac` style)
ruby -e 'puts File.open($< .filename).readlines.reverse' file.txt
 
# print matched string from lines, matching the pattern
ruby -ne 'puts $_.scan(/^\w+/)' /etc/passwd
 
# triple space a file and reverse order of lines
ruby -e '$,="\n\n\n"; puts File.readlines($<.filename).reverse.join' file.txt
 
# print first line of a file (emulate 'head -1')
ruby -ne 'puts $_; break' file.txt
ruby -pe '$. == 1 or break' file.txt
 
# print last line of a file (emulates 'tail -1')
ruby -ne 'END{puts $_}' file.txt
 
# print last line number (emulates 'wc -l')
ruby -e 'loop{gets or break}; puts $.' file.txt
 
# print only lines that match a regular expression (emulates 'grep')
ruby -pe 'next if not /regex/' file.txt
 
# print only lines that do not match a regular expression (emulates 'grep -v')
ruby -pe 'next if /regex/' file.txt
 
# print section of file between two regular expressions, /^root/ and /^nobody/
ruby -ne 'puts $_ if /^root/../^nobody/' file.txt
 
# print file and remove duplicate, consecutive lines from a file (emulates 'uniq')
ruby -ne '$_.eql? $; or puts $_;$; = $_;' file.txt
 
# print file except for blank lines
ruby -pe 'next if $_.chomp.empty?' file.txt
ruby -pe 'next if /^\s*$/' file.txt
ruby -pe 'next if $_.split(/\S+/).size < 2' file.txt
 
# print file except for lines, starting with digit (unclear and inefficient)
ruby -pe 'next if (48..57).to_a.include?($_.split(//)[0][0])' file.txt
 
# delete all leading blank lines at top of file
ruby -pe '$,="$." if not $_.chomp.empty?; $, or next' file.txt
 
# print section of file from regex to end of file
ruby -pe '$,="$." if /regex/; $, or next' file.txt
 
# delete leading and trailing whitespace from each line
ruby -pe '$_.strip!.sub!(/$/, "\n")' file.txt
ruby -ne 'puts $_.strip! + $/' file.txt
 
# delete leading whitespace from the beginning of each line
ruby -ne 'puts $_.lstrip! || $_' file.txt
 
# convert DOS newlines (CR/LF) to Unix format (LF)
ruby -i -pe 'sub(/\r\n/, "\n")' file.txt
Written by Vidul in: Ruby, oneliners, scripts |

compare the ip address of different hostnames

Jul 20
2007
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require "socket"
 
unless ARGV.size == 2
 raise ArgumentError,
   "Expected two hostnames, got #{ARGV.size}"
end
 
h1,h2 = ARGV
 
begin
  h1,h2 = Socket::getaddrinfo(h1, 7)[0][3], Socket::getaddrinfo(h2, 7)[0][3]
rescue
  print "#{$!}...\texiting\n"
  exit
end
 
if h1.eql? h2
  puts "hosts have the same ip address: #{h1}"
else
  puts "hosts differ: #{h1} #{h2}"
end
Written by Vidul in: SA, scripts |

nmap output cleaner

Jul 19
2007
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arg = ARGV.join(" ")
arg.empty? and exit
 
puts %x[nmap #{arg} 2>/dev/null].scan(/^\d+.+/)
Written by Vidul in: Ruby, scripts |

1..666

Jul 19
2007
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irb console

$.=0; (1..666).to_a.inject(1){|res, i| res += i}.to_s.split(//).collect{|i| $. += i.to_i}; STDOUT.puts$
Written by Vidul in: Ruby, oneliners, scripts |

JAPH

Jul 19
2007
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$_->[/^(?>(.)?(.)+.*)(?!\1)(??{print(($1..$2)[9,0,15,7])})/]
Written by Vidul in: JAPH, Perl |

Fibonacci numbers in Ruby and Perl

Jul 19
2007
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#!/usr/bin/env ruby

x=1;loop{p$.+=x=$.-x}

. #!/usr/bin/env perl

print$}+=$.=$}-$.||1while.1
Written by Vidul in: Perl, Ruby |

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