Ruby solution for week 97, part 1

2 files changed, 47 insertions, 0 deletions

diff --git a/challenge-097/abigail/README.md b/challenge-097/abigail/README.md
index ef9eaa5301..0e2295286a 100644
--- a/challenge-097/abigail/README.md
+++ b/challenge-097/abigail/README.md
@@ -31,6 +31,7 @@ to indicate the left shift.
 * [Node.js](node/ch-1.js)
 * [Perl](perl/ch-1.pl)
 * [Python](python/ch-1.py)
+* [Ruby](ruby/ch-1.rb)
 
 ### Blog
 
diff --git a/challenge-097/abigail/ruby/ch-1.rb b/challenge-097/abigail/ruby/ch-1.rb
new file mode 100644
index 0000000000..1225bd290c
--- /dev/null
+++ b/challenge-097/abigail/ruby/ch-1.rb
@@ -0,0 +1,46 @@
+#!/usr/bin/ruby
+
+#
+# See ../README.md
+#
+ 
+#
+# Run as: ruby ch-1.rb -s SHIFT < input-file
+#
+
+require 'optparse'
+
+NR_OF_LETTERS = 26
+
+
+#
+# Parse and validate options
+#
+params = ARGV . getopts ('s:')
+shift  = params ["s"] ? params ["s"] . to_i % NR_OF_LETTERS : -1
+
+if shift < 0
+    STDERR . puts "Requires a -s SHIFT option"
+    exit 1
+end
+
+
+#
+# Method to shift an upper case letter
+#
+def shift_letter (letter, shift)
+    n = letter . ord - shift
+    if   n < 'A' . ord
+    then n = n + NR_OF_LETTERS
+    end
+    return n . chr
+end
+
+
+#
+# Iterate over the input, shift capital letters
+#
+ARGF . each_line do |line|
+     line = line . gsub (/[A-Z]/) {|_| shift_letter _, shift}
+     puts line
+end