Command line program for Aquamacs

aquamacs

#!/usr/bin/env ruby

######################################################################
#
# Open the given file names in Aquamacs.
#
# If the user already has an Aquamacs process open, use it.
# Otherwise, fire up a new one.  Only Aquamacs instances without a
# controlling terminal (i.e., those running in a window) will be
# selected.
#
# Note: We assume the server socket lives in the standard location:
# /tmp/emacs<uid>/server.
#
######################################################################

require 'optparse'
require 'tmpdir'

class App
  def initialize
    @emacs = find_emacs
    @socket = find_socket
    @verbose = false
  end

  attr_reader :emacs, :socket, :verbose

  def run(args)
    parse_args(args)

    emacs or
      abort "Cannot find emacs. Set EMACS, or use -e option."

    puts "Using emacs: #{emacs}" if verbose

    if aquamacs_running?
      exec emacs_path('bin/emacsclient'), '--no-wait', "--socket-name=#{socket}", *args
    else
      puts 'Starting Aquamacs...'

      # We can't just use the open command, as it will always open
      # Aquamacs as the logged-in user, and we want to run as the user who
      # ran this program (e.g., for sudo).

      # Fork so it runs in the background.
      fork do
        # Lose the controlling terminal.
        Process.setsid

        # Silence errors.  If we run this as someone other than the
        # logged-in user, Aquamacs gets a permissions error trying to
        # register itself as a service and cries loudly.
        STDERR.reopen('/dev/null') unless verbose
        exec emacs_path('Aquamacs', 'Aquamacs Emacs'), *args
      end
    end
  end

  def parse_args(args)
    parser = OptionParser.new do |parser|
      parser.on('-e', '--emacs=PATH', "Path to Aquamacs. Default: #{emacs}") { |path| @emacs = path }
      parser.on('-s', '--socket=PATH', "Path to server socket. Default: #{socket}") { |path| @socket = path }
      parser.on('-v', '--verbose', "Show all errors.") { |path| @verbose = true }
    end
    parser.parse!(args)
    args.size >= 1 or
      abort 'No files given.'
  end

  def find_emacs
    emacs = ENV['EMACS'] and
      return emacs

    ['Aquamacs.app', 'Aquamacs Emacs.app'].each do |app_name|
      ['~/Applications', '/Applications'].each do |app_path|
        path = File.expand_path("#{app_path}/#{app_name}")
        return path if File.exist?(path)
      end
    end
    nil
  end

  def find_socket
    tmp_dir = Dir.tmpdir
    "#{tmp_dir}/emacs#{Process.uid}/server"
  end

  def emacs_path(*names)
    names.each do |name|
      path = "#{emacs}/Contents/MacOS/#{name}"
      return path if File.exist?(path)
    end
    nil
  end

  def aquamacs_running?
    `ps -U #{ENV['USER']} -xwwo tpgid,command`.each_line do |line|
      tpgid, command = *line.split(nil, 2)

      # Assume Aquamacs instances with a controlling terminal are
      # running inside a terminal window.  Any instances we launch will
      # have no controlling terminal.
      return true if command =~ /\A#{Regexp.escape emacs}/ && tpgid == '0'
    end
    false
  end
end

App.new.run(ARGV)