TweetFollow Us on Twitter

An Editor to Create DropScript Droplets

Volume Number: 19 (2003)
Issue Number: 5
Column Tag: Programming

An Editor to Create DropScript Droplets

Making the DropScript experience more like the MacPerl experience

by Larry Taylor

A Problem

I love MacPerl. I even wrote an article for MacTech extolling its virtues (Sept. 2000). MacPerl is a Mac port of Perl, initially a UNIX scripting language. Being UNIX based, OS X comes with a Perl implementation and there have been many excellent MacTech articles recently touting its uses. Rich Morin has a whole series (Aug. & Sept. 2002, Jan. 2003); Jeff Clites (April 2000), Paul Ammann (June 2002) and Joe Zobkiw (Sept. 2002) have articles as well. By the time this appears, there will undoubtedly be more. The basic idea is simple. Write a Perl script to do something useful, make the file executable, set it to be opened by the Terminal application and you're ready to go. Double click on the file and the Perl script runs, just like simple droplets in MacPerl.

However many scripts process files or folders. The great thing about a MacPerl droplet is that you can drag the files/folders onto it and get the path names of the dropped collection in the @ARGV array. My article depended on this behavior and I really miss it in OS X.

Then Wilfredo Sanchez wrote a program called DropScript to make droplets. He wrote a nice MacTech article (Aug. 2001) about it. Additional information can be found in the README file in the examples folder that comes with the DropScript distribution. DropScript can make droplets to run Bourne shell scripts, the case Sanchez concentrates on, or Perl scripts, tcl scripts, Python scripts ... . Just set the shebang line correctly and you're off.

My main gripe with DropScript comes from my bad habit of coding quickly. Every time I changed the code I had to re-run the file through DropScript and, if I forgot to delete the old droplet, I was merely informed that the droplet existed and I had to go back, delete the old droplet and run my file through DropScript yet again. Not an appealing scenario! Using MacPerl you just opened the droplet in MacPerl, typed in your new code, saved it and the behavior of the droplet reflected your changes immediately.

A second issue is the end-of-line problem. DropScript expects the scripts dropped on it to have UNIX end-of-lines, \n, whereas it is notoriously easy to be using a file with Mac end-of-lines, \r. TextEdit or BBEdit will save files as 'TEXT' with UNIX eol's once you have such a file and BBEdit will even convert an old Mac file for you, so the issue is not serious as long as you remember to do the switch.

A Solution

Reading Sanchez's article more carefully I realized that these droplets were applications and applications are folders under OS X. You can see the folder by option-clicking the app and selecting Show Package Contents from the contextual menu. Your application opens as a folder which contains a single folder called Contents, and DropScript copies the script to the file /Contents/Resources/script. Experimentation showed that I could edit this file directly and run the new code without going through DropScript again and the eol-problem took care of itself.

Eventually it occurred to me that I could write a droplet-Perl-script to avoid the option-click process, hence Droplet Editor, the focus of this article. Drop a droplet onto Droplet Editor and the script file is opened. Droplet Editor also supports making a new droplet.

First Steps

Since Droplet Editor itself is a droplet, we are going to begin with a minimal version of the code and then use it to finish the whole project. Step one is to acquire DropScript from

www.apple.com/downloads/macosx/unix_open_source/dropscript.html

and put the application somewhere - it needs no installer. I put mine in a folder DropScript inside my Applications folder, but it doesn't have to go there. Make a copy of the program, rename it Droplet Editor and put it anywhere you have read/write permissions. Now option-click Droplet Editor and select Show Package Contents from the contextual menu. Open the Contents folder and then the Resources folder. Open the file script in BBEdit or TextEdit by dragging it to the dock onto one of these apps.

Delete the code currently in the file and enter the following code.

#!/usr/bin/perl
use strict;
#############  Fixed paths #############
my($editor_path)="/Applications/BBEdit/BBEdit.app";
my($emulator_path)="/Contents/Resources/script";
my($aa);
foreach $aa (@ARGV){
  if( $aa=~m/\.app$/ && -f $aa.$emulator_path) {
    my($app)=substr($aa,rindex($aa,"/")+1);
    print"Opening the script for \"$app\".\n";
    $aa=$aa.$emulator_path;
    system("open -a \"$editor_path\" \"$aa\"");
    }
  }

If your editor of choice is located elsewhere, change the $editor_path. Save your text and close the file. Add Droplet Editor to the dock. Track down and open the Console program, usually in /Applications/Utilities/, since messages from droplets show up here. Now drag the Droplet Editor application onto its icon in the dock and your file will pop open in BBEdit or to whatever word processor your $editor_path points. If you drop any other droplet onto Droplet Editor the script for that droplet opens. If you have errors in this initial Droplet Editor script, the error messages show up in the Console window. Reopen the script the hard way and fix the errors. Repeat as needed until the script opens.

Completing the Project

The rest of the project involves adding bells and whistles to this basic code, especially the mechanism to create new droplets. We do this by treating the drop of anything that is not a droplet as a request to make a new droplet, named after the dropped object. If you drop a file or a folder named foo which is not a droplet, you get a new droplet, Dropfoo, in the same folder as the file or inside the folder. This bit of the project is handled by a subroutine make_basic_droplet which takes two arguments, the folder in which to put the new droplet and its name. You can set the extension of the dropped object to specify what sort of script you want as indicated below.

First add the path to your copy of DropScript to the "Fixed paths" list.

my($dropscript_path)="/Applications/DropScript/DropScript.app";
At the bottom of the foreach-loop add the following two elsif's:
  elsif( -d $aa) {
    my($name)=substr($aa,rindex($aa,"/")+1);
    make_basic_droplet($aa,$name);
    }
  elsif( -f $aa) { 
    my($dir)=substr($aa,0,rindex($aa,"/"));
    my($name)=substr($aa,rindex($aa,"/")+1);
    make_basic_droplet($dir,$name);
    }

This finishes the project except for writing the code for the subroutine. Begin with three lines.

sub make_basic_droplet{
my($dir)=shift(@_);
my($name)=shift(@_);

Next we determine the type of script being requested. The next four lines extract the extension of the dropped object and do some checking. If the eventual name of the script would start with a period, which would make the resulting droplet invisible, we bail.

my($script_type);
if( $name=~s/(\.[^\.]*)$//) {$script_type=$1;} 
else {$script_type='.default';}
if($name eq "") {return;}

Next we want to determine if we recognize the extension. We begin by building a list of extensions we recognize. Return to the top of the file and just after the "Fixed paths" add some lines

################# Script types #################
my(%script_type);
$script_type{'.default'}="#!/usr/bin/perl";
$script_type{'.perl'}="#!/usr/bin/perl";
$script_type{'.py'}="#!/usr/bin/python";
$script_type{'.sh'}="#!/bin/sh";
$script_type{'.tcl'}="#!/usr/bin/tclsh";
##################################

The first line is required; the rest are optional. I mostly write Perl scripts so my ".default" script_type is the Perl shebang line, but I have included extensions for Bourne shell scripts, ".sh", Python scripts, ".py" and tcl scripts, ".tcl". If the dropped file/folder has a recognized extension, the shebang line in the new script will be the corresponding %script_type. A non-recognized extension, including no extension, defaults to ".default". You are of course free to add/delete/modify these entries to suit your needs. As an example, if you always use the -w flag in Perl you might want to change the '.perl' entry to $script_type{'.perl'}="#!/usr/bin/perl -w";

Now return to the bottom of the file and add the line

if( !exists($script_type{$script_type})) {$script_type='.default';}

which sets the variable $script_type to either ".default" or the dropped object's extension if we recognize it. Then add ten more lines which construct the droplet name and check that the name isn't in use. If it is we just keep adding a number to the name until we get a name with no conflicts. This prevents accidental destruction of files, but if you never make such mistakes, skip the nine lines beginning "if( -d ...".

my($aa)=$dir."/Drop".$name.".app";
if( -d $aa) {
  print"\n\nThere already is a droplet \"Drop",$name,"\".\n\n";
  my($nextname)=1;
  my($Name)=$name;
  while( -d $aa) {
    $name=$Name.$nextname;
    $aa=$dir."/Drop".$name.".app";$nextname++;
    }
  }

DropScript is expecting a file to copy into the new droplet, so next we produce the required file. If there already is a script file then we read it into the @script array and change any Mac eol's to UNIX ones, avoiding any eol-problems. If there is not already a script file we just set @script to put in a couple of UNIX eol's. Then we write a file, $outfile, which DropScript will copy into the droplet. If you already had a script with a shebang line, you now start with two. We do this because Apple does not always put programs like Perl in their standard places so if you are porting a Perl script, its shebang line is probably wrong. However, it may have flags you will need to copy so it's nice to see what the old one was.

my($outfile)=$dir."/".$name.$script_type;
my(@script);
if( -f $outfile) {
  open(IN,$outfile) or die($!);
  @script=<IN>;
  close(IN);
  my($xx);
  foreach $xx (@script) {$xx=~s/\r/\n/g;}
  }
else {push(@script,"\n\n");}
$outfile=$dir."/".$name.".default";
open(OUT,">$outfile") or die($!);
print OUT $script_type{$script_type},"\n";
print OUT @script;
close(OUT);
undef(@script);

The next step tells DropScript to make the droplet and announces the birth.

system("open -a \"$dropscript_path\"  \"$outfile\"");
print"\n\nCreating new droplet: \"Drop",$name,"\".\n\n";

The final bit of code is designed to overcome a threading problem. DropScript requests that the file $outfile be copied to the file $AA, but the copy may not take place immediately. We want to delete the file $outfile from which we are copying, but we shouldn't do this until after the copy is finished. The empty while-loops just wait until various files/folders are created and the $AA file has non-zero length. Then we wait some more until $AA and $outfile are the same, which we check using the UNIX diff command. The >/dev/null bit is UNIX for "throw away the output of the diff command" (which is a list of the differences). Finally we delete $outfile.

while( ! -d "$aa") {;}
my($AA)=$aa.$emulator_path;
while( ! -f "$AA") { ;}
my($BB)=$aa."/Contents/Info.plist";
while( ! -f "$BB") { ;}
while( -z "$AA") { ;}
while (system("diff \"$AA\" \"$outfile\" > /dev/null")/256 !=0) {;}
unlink($outfile);

We end by opening the script of our new droplet and closing the brace for our subroutine.

system("open -a \"$editor_path\" \"$AA\"");
}

Some Final Remarks

DropScript-droplets have two annoying features. One bit of annoyance is that print commands go to the Console program which may be hidden or may not even be open, so you'll think there was no output. To fix this, add the line

system("open \"/Applications/Utilities/Console.app\"");

up near the start of your scripts. Other programs are also writing to this window so your output may get sandwiched between other output which is why I have the \n\n's around my text to make it easier to find.

The other annoyance is that the working directory of your droplet is root, whereas MacPerl sets it to the folder containing the droplet. If your code has path names beginning with "./" these droplets probably will not work. Other scripts may try to write files to the root directory which often fails and is never where you are looking for them anyway. Calling pwd in your code probably means it will break as well. The solution is to get the folder containing the droplet, and then you can do a chdir. The Perl variable $0 contains the path to the code file, but under OS X this file is several folders deep inside the droplet, which is a folder. The following code snippet yields the folder containing the droplet (without the final "/").

my($app)=$0; 
$app=substr($app,0,rindex($app,"/Contents")); $app=substr($app,0,rindex($app,"/"));

Initially I ended this article with a list of features enjoyed by MacPerl droplets that I would like to see in DropScript droplets. An anonymous editor saw this version and pointed out that many of these features had been carbonized in recent releases of MacPerl. A bit of experimentation revealed that if you have chased down and installed both a version of Perl newer than the Apple-included version, and the carbonized MacPerl modules, then you can have many of the MacPerl features such as Ask, Answer, Pick, etc. in your new droplets. These installations are not for the faint-of-heart, but if you google around you can dig up the necessary files and lots of chit-chat on problems/solutions.

Happy scripting!


Larry Taylor is a research mathematician and professor who spends too much time fooling around with this sort of thing. More stuff at <www.nd.edu/~taylor>.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Capo 3.2 - Slow down and learn to play y...
Capo lets you slow down your favorite songs so you can hear the notes and learn how they are played. With Capo, you can quickly tab out your songs atop a highly-detailed OpenCL-powered spectrogram... Read more
OmniOutliner 4.2.3 - Organize your ideas...
OmniOutliner is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
pwSafe 4.0.1 - Secure password managemen...
pwSafe provides simple and secure password management across devices and computers. pwSafe uses iCloud to keep your password databases backed-up and synced between Macs and iOS devices. It is... Read more
WALTR 1.5.4 - Drag-and-drop any media fi...
WALTR is designed to make it easy to upload and convert any music or video file to an iPad or iPhone format for native playback. It supports a huge variety of media file types, including MP3, MP4,... Read more
Audio Hijack 3.1 - Record and enhance au...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
PopChar 7.1 - Floating window shows avai...
We're also selling a 5-license family pack for only $25.99! PopChar helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to... Read more
BBEdit 11.1.1 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
Picasa 3.9.139 - Organize, edit, and sha...
Picasa and Picasa Web Albums allows you to organize, edit, and upload your photos to the Web from your computer in quick, simple steps. Arrange your photos into folders and albums and erase their... Read more
Mac DVDRipper Pro 5.0.5 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
NetShade 6.2 - Browse privately using an...
This promotion is for NetShade and 1 year of Proxy and VPN services NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN... Read more

Block Fortress has a Big New Update for...
Block Fortress is a survival-style game that's as fun as it is blocky. It's also just gotten a rather sizeable update that adds a lot more cool stuff. [Read more] | Read more »
Simple and Surreal Star Base Sim rymdkap...
I really like rymdkapsel. Not just because I'm a sucker for games that are cleverly simple or highly stylisitc, but because it's fun and challenging. Actually it's extremely challenging, which is why I was excited to learn that it's getting a couple... | Read more »
Check out the anticipated Angel Stone in...
Fincon has finally revealed Angel Stone in action in the first ever official gameplay trailer for the anticipated hack and slasher. Angel Stone is set in a post-apocalyptic world in which humanity is in danger of being wiped out by the demonic... | Read more »
Moleskine Timepage is an All-New Calenda...
Moleskine Timepage is a bit of a departure for the notebook manufacturer (since it has little to do with notebooks), but it certainly carries their simple and elegant style quite well. [Read more] | Read more »
Jog on Over and Check Out the New Runtas...
Runtastic has put out a fair number of apps to help you sleep, track excercise, and train various parts of your body. Now it's time for your legs to have their own time in the spotlight with Runtastic Leg Trainer. [Read more] | Read more »
It's Lights Out in the Upcoming Pla...
Ember’s Journey is a stark puzzle platformer with a twist: the entire game is played in darkness. The only light you can see by is the one emanating from your own character. [Read more] | Read more »
MooVee - Your Movies Guru (Entertainmen...
MooVee - Your Movies Guru 1.0 Device: iOS iPhone Category: Entertainment Price: $1.99, Version: 1.0 (iTunes) Description: MooVee helps you effortlessly manage your movies, on your iPhone. | Read more »
Geometry Wars 3: Dimensions (Games)
Geometry Wars 3: Dimensions 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enjoy the next chapter in the award-winning Geometry Wars franchise and enjoy stunning, console-quality... | Read more »
CHAOS RINGS Ⅲ (Games)
CHAOS RINGS Ⅲ 1.0.0 Device: iOS Universal Category: Games Price: $19.99, Version: 1.0.0 (iTunes) Description: The newest addition to the popular smartphone RPG series is finally here! ・CHAOS RINGS Overview | Read more »
The Popular Insight Series of Travel Gui...
Getting around in a country when you can't understand the primary language can be tough. Fortunately there are several options available to help wold travellers with the important stuff like giving directions to a cab driver or asking where the... | Read more »

Price Scanner via MacPrices.net

Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
13-inch 2.4GHz Retina MacBook Pro (refurbishe...
The Apple Store has 2013 Apple Certified Refurbished 13″ 2.4GHz/128GB Retina MacBook Pros available for $879–$320 off original MSRP. Apple’s one-year warranty is standard, and shipping is free: - 13... Read more
Apple refurbished iPad Air 2s now available f...
The Apple Store is now offering Apple Certified Refurbished iPad Air 2s for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: -... Read more
MacBook Airs on sale for up to $80 off MSRP
Save up to $80 on the purchase of a new 2015 13″ or 11″ 1.6GHz MacBook Air at the following resellers. Shipping is free with each model: 11" 128GB MSRP $899 11" 256GB... Read more
Free Glide Live Video Messaging App Brings Ne...
Glide, an Israeli startup whose popular live video messenger has attracted more than 15 million users, has released significant updates to its free iOS app. Glide for iOS now gives users more control... Read more
Top Markets Saturation To Slow Global Smartph...
According to a new mobile phone forecast from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, smartphone shipments are expected to grow 11.3% in 2015 — down from 27... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Apple refurbished 2014 13-inch Retina MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ Retina MacBook Pros available for up to $400 off original MSRP, starting at $979. An Apple one-year warranty is included with each model, and... Read more
What Would the ideal Apple Productivity Platf...
For the past four years I’ve kept a foot in both the Mac and iPad camps respectively. my daily computing hours divided about 50/50 between the two devices with remarkable consistency. However, there’... Read more

Jobs Board

Senior Software Engineer - *Apple* SIM - Ap...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
*Apple* Pay Support Readiness Project Manage...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Program Manager, *Apple* Community Support...
**Job Summary** Apple Support Communities ( discussions. apple .com) helps customers get the most from their Apple products and services by providing access to Read more
Senior Data Scientist, *Apple* Retail - Onl...
**Job Summary** Apple Retail - Online sells Apple products to customers around the world. In addition to selling Apple products with unique services such as iPad Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.