add i for line-number

Readme.md

@@ -24,6 +24,10 @@ A few simple examples.<br/>
     ls -al | grep foo
     ls -al | pru /foo/
 
+    # grep --- all lines including current date
+    ls -al | ???
+    ls -al | pru 'include?(Time.now.strftime("%Y-%m-%d"))'
+
     # grep --- all lines including foo but not self
     ps -ef | grep foo | grep -v grep
     ps -ef | pru 'include?("foo") and not include?("pru")'
@@ -44,6 +48,9 @@ A few simple examples.<br/>
     ls -al | sed 's/5/five/'
     ls -al | pru 'gsub(/5/,"five")'
 
+    # every second line
+    ls -al | pru 'i % 2 == 0'
+
 
 Author
 ======

lib/pru.rb

@@ -2,6 +2,7 @@ class Pru
   VERSION = File.read( File.join(File.dirname(__FILE__),'..','VERSION') ).strip
 
   def self.map(io, code)
+    i = 1
     io.readlines.each do |line|
       result = line.instance_exec{ eval(code) }
       if result == true
@@ -11,6 +12,7 @@ def self.map(io, code)
       elsif result
         yield result
       end
+      i += 1
     end
   end
 

spec/pru_spec.rb

@@ -17,6 +17,10 @@
     `ls -l | ./bin/pru /G/`.split("\n").size.should == 2
   end
 
+  it "can selects via i" do
+    `ls -l | ./bin/pru 'i'`.split("\n")[0...3].should == ["1","2","3"]
+  end
+
   it "maps" do
     `echo abc | ./bin/pru 'gsub(/a/,"b")'`.should == "bbc\n"
   end