Pretty printing the interfaces from classes in jar (java archive) files.

jar_classes.sh

#!/bin/bash

# Pic of output at https://twitter.com/josh_cheek/status/693598961026793472

jarfile="$1"
if test -z "$jarfile"
then
  echo "You must provide a jarfile as an argument" >&2
  exit 1
elif test ! -f "$jarfile"
then
  echo "The file you provided" `ruby -e 'print ARGV[0].inspect' "$jarfile"` "does not map to a jarfile" >&2
  exit 1
fi

# do the work in a temporary directory
dir=`mktemp -d -t jar-prettyprint`
cp "$jarfile" "$dir"
pushd "$dir" >/dev/null

# extract the contents of the jar
jar xf "$jarfile"

# Pretty print the class files
find . -type f -name '*.class' | # list the files that end in .class
  xargs javap |                  # disassemble them
  ruby -r coderay -ne '
    # Aggregate disassembled info in @code
    BEGIN { @code = "" }

    # Pretty print the disassembled code and reset the var
    def next_class
      print CodeRay.encode(@code, :java, :terminal)
      @code = ""
    end

    # Print previous code and header for next piece of code
    if /^Compiled from/
      next_class
      puts "\e[1;92m#{$_.chomp}\e[0m"
    else
      @code << $_
    end

    # Print last chunk of code (there is no header after it to trigger this)
    END { next_class }
  '

# Return from the temp dir
popd >/dev/null

# Clean up the temp dir
rm -r "$dir"