devscript: support -t opt in list_running_app_ids

and refactor

developer/bin/list_running_app_ids

@@ -3,45 +3,105 @@
 # list_running_app_ids
 #
 
-if ARGV.length > 0
-  puts <<-EOS
-list_running_app_ids
+###
+### dependencies
+###
 
-Print a list of currently running Applications and associated Bundle IDs,
-which may be useful in a Cask uninstall stanza, eg
+require 'open3'
+require 'set'
+
+###
+### globals
+###
+
+$opt_test = nil
+
+###
+### methods
+###
+
+def usage
+  <<-EOS
+list_running_app_ids [ -t <bundle-id> ]
+
+Print a list of currently running Applications and associated
+Bundle IDs, which may be useful in a Cask uninstall stanza, eg
 
     uninstall :quit => 'bundle.id.goes.here'
 
 Applications attributed to Apple are excluded from the output.
 
+With optional "-t <bundle-id>", silently test if a given app
+is running, exiting with an error code if not.
+
 See CONTRIBUTING.md for more information.
 
 EOS
-  exit
 end
 
-require 'open3'
-
-running = {}
-out, err, status = Open3.capture3('/usr/bin/osascript', '-e', 'tell application "System Events" to get (name, bundle identifier, unix id) of every process')
-if status.exitstatus > 0
-  puts err
-  exit status.exitstatus
+def process_args
+  while ! ARGV.empty? do
+    if ARGV.first =~ /^-+t(?:est)?$/ and ARGV.length > 1
+      ARGV.shift
+      $opt_test = ARGV.shift
+    elsif ARGV.first =~ /^-+h(?:elp)?$/
+      puts usage
+      exit 0
+    else
+      puts usage
+      exit 1
+    end
+  end
 end
 
-out = out.split(', ')
-one_third  = out.length / 3
-app_names  = out.shift(one_third)
-bundle_ids = out.shift(one_third)
-unix_ids   = out.shift(one_third)
-
-app_names.zip(bundle_ids, unix_ids).each do |app_name, bundle_id, unix_id|
-  next if bundle_id =~ %r{^com\.apple\.}
-  next if app_name == 'osascript'   # this script itself
-  bundle_id.gsub!(/^(missing value)$/, '<\1>')
-  running["#{bundle_id}\t#{app_name}"] = 1
+def load_apps
+  out, err, status = Open3.capture3('/usr/bin/osascript', '-e', 'tell application "System Events" to get (name, bundle identifier, unix id) of every process')
+  if status.exitstatus > 0
+    puts err
+    exit status.exitstatus
+  end
+  out = out.split(', ')
+  one_third   = out.length / 3
+  @app_names  = out.shift(one_third)
+  @bundle_ids = out.shift(one_third)
+  @unix_ids   = out.shift(one_third)
 end
 
-puts "bundle_id\tapp_name\n"
-puts "--------------------------------------\n"
-puts running.keys.sort
+def test_app(bundle)
+  @bundle_ids.include?(bundle) ? 0 : 1
+end
+
+def excluded_bundle_id(bundle_id)
+  %r{^com\.apple\.}.match(bundle_id)
+end
+
+def excluded_app_name(app_name)
+  %r{^osascript$}.match(app_name)   # this script itself
+end
+
+def report_apps
+  running = Set.new
+  @app_names.zip(@bundle_ids, @unix_ids).each do |app_name, bundle_id, unix_id|
+    next if excluded_bundle_id bundle_id
+    next if excluded_app_name app_name
+    bundle_id.gsub!(/^(missing value)$/, '<\1>')
+    running.add "#{bundle_id}\t#{app_name}"
+  end
+
+  puts "bundle_id\tapp_name\n"
+  puts "--------------------------------------\n"
+  puts running.to_a.sort
+end
+
+###
+### main
+###
+
+process_args
+load_apps
+
+if $opt_test
+  exit test_app($opt_test)
+else
+  report_apps
+end