Add ruby-one-liners

Readme.mdown

@@ -25,6 +25,7 @@ Playgrounds
 * [ready-for-zero-challenges](http://github.com/JoshCheek/Play/tree/master/ready-for-zero-challenges/) My solutions to [https://www.readyforzero.com/challenge](https://www.readyforzero.com/challenge).
 * [ruby-overloadable](http://github.com/JoshCheek/Play/tree/master/ruby-overloadable/) Give Ruby method overloading
 * [ruby-golf](http://github.com/JoshCheek/Play/tree/master/ruby-golf/) Solutions for [Ruby Golf](http://rubysource.com/ruby-golf/)
+* [ruby-one-liners](http://github.com/JoshCheek/Play/tree/master/ruby-one-liners/) Using Ruby for command line one-liners (where you might normally use sed or awk).
 * [ruby-s](http://github.com/JoshCheek/Play/tree/master/ruby-s/) How to use ruby's -s flag for simple command line args.
 * [self-referential-hash](http://github.com/JoshCheek/Play/tree/master/self-referential-hash/) Hash where you can declare one key references another.
 * [sikulidraw](http://github.com/JoshCheek/Play/tree/master/sikulidraw/) Generate commands for Sikuli such that it draws a picture on the screen, given that the mouse is a 1px pencil.

ruby-one-liners/Readme.md

@@ -0,0 +1,120 @@
+For Chicago Ruby's [Hack Night](http://www.meetup.com/ChicagoRuby/events/43150262/) on 15 Dec 2011:
+
+Inspired by the [one-line scripts for awk](http://www.pement.org/awk/awk1line.txt),
+we'll write Ruby programs to do things
+like double-space a file or add line numbers to the file or center the text in each
+line of a file.  The challenge is to write the shortest possible program that works
+for each of these tasks:
+
+### doublespace a file
+
+      ruby -lpe '$_<<"\n"'
+
+
+### add line numbers to each input file
+
+      # not happy with this one, but couldn't figure out how to get ARGF to reset $.
+      # (also, 1.9 only)
+      ruby -e 'l=-> line {puts "#$. #{line}"}; ARGV.each { |name| File.foreach name, &l}; $stdin.each &l'
+
+
+### add line numbers for all files together
+
+     ruby -lne 'print "#$. #$_"'
+     ruby -lpe '$_.prepend "#$. "'
+
+
+### add line numbers only for nonblank lines
+
+    ruby -lpe '/^$/ ? $.-=1 : $_ = "#$. :#$_"'
+
+
+### count lines in file
+
+    ruby -ne 'END{puts $.}'
+
+
+### count words in file
+
+    ruby -ane 'w = (w||0) + $F.size; END { p w }'
+
+
+### output total number of lines that contain 'abc'
+
+    ruby -ne 'BEGIN { num = 0 }; num += 1 if $_ =~ /abc/; END { p num }'
+    ruby -e 'p ARGF.readlines.grep(/abc/).size'
+    ruby -ne 'w=(w||0)+1 if /abc/; END{p w}'
+
+
+### output a string of 43 X's
+
+    ruby -e 'puts "X"*43'
+
+
+### insert a string of 3 X's after column 6 of each input line
+
+    ruby -ple '$_.insert 6, "xxx" if $_.size > 6'
+
+
+### delete leading whitespace from beginning of each line
+
+    ruby -pe '$_.sub! /^\s+/, ""'
+
+
+### delete trailing whitespace from end of each line
+
+    ruby -pe '$_.gsub! /\s+$/, "\n"'
+
+
+### add leading blanks to right-align all text in 80-column width
+
+    ruby -pe '$_ =  "%80s\n" % $_.chomp'
+
+
+### add leading and trailing blanks to center each line in 80 columns
+
+    ruby -lne 'printf "%80s\n", $_'
+
+
+### reverse the text in each line
+
+    ruby -lpe '$_.reverse!'
+
+
+### concatenate every 5 lines of input, using , as separator
+
+    ruby -e 'ARGF.each_slice(5) { |lines| puts lines.map(&:chomp).join(",") }'
+
+
+### print first 10 lines of file
+
+    ruby -pe 'exit if $. > 10'
+
+
+### print last 10 lines of file
+
+    ruby -ne 'puts $_ if $. > 10'
+
+
+### print line 13 of file
+
+    ruby -ne 'puts $_ if $. == 13'
+
+
+### delete blank lines from file
+
+    ruby -ne 'puts $_ unless $_ == "\n"'
+
+
+### delete consecutive duplicate lines from file
+
+    ruby -ne 'puts $_ if /^[^\n]/../^$/'
+
+
+### delete any duplicate lines from file
+
+    # consecutive duplicates
+    ruby -lne 'BEGIN{last=""};puts last=$_ unless last==$_'
+
+    # any duplicate in input
+    ruby -lne 'BEGIN{lines=Hash.new{|h,l|puts h[l]=l}};lines[$_]'