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

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.

use strict;
#############  Fixed paths #############
foreach $aa (@ARGV){
  if( $aa=~m/\.app$/ && -f $aa.$emulator_path) {
    print"Opening the script for \"$app\".\n";
    system("open -a \"$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.

At the bottom of the foreach-loop add the following two elsif's:
  elsif( -d $aa) {
  elsif( -f $aa) { 

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

sub make_basic_droplet{

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.

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 #################

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 ...".

if( -d $aa) {
  print"\n\nThere already is a droplet \"Drop",$name,"\".\n\n";
  while( -d $aa) {

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.

if( -f $outfile) {
  open(IN,$outfile) or die($!);
  foreach $xx (@script) {$xx=~s/\r/\n/g;}
else {push(@script,"\n\n");}
open(OUT,">$outfile") or die($!);
print OUT $script_type{$script_type},"\n";
print OUT @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 "$aa") {;}
while( ! -f "$AA") { ;}
while( ! -f "$BB") { ;}
while( -z "$AA") { ;}
while (system("diff \"$AA\" \"$outfile\" > /dev/null")/256 !=0) {;}

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/\"");

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 "/").

$app=substr($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 <>.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Between 2 Taps - Tap for Tap interview M...
Hello, and welcome back to Between 2 Taps, Tap for Tap’s Indie Dev interview series. [Read more] | Read more »
Facility 47 (Games)
Facility 47 1.0.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.1 (iTunes) Description: You wake up alone and freezing in an icy cell. You try the cell door but it’s locked, it seems that you are stuck with no... | Read more »
The best Photoshop alternative on iPad
Instagram and Lightroom are great and all, but sometimes people need to get extra creative with their image editing.Like, Photoshop creative. If you're one of these people, take a look at our pick for the best mobile Photoshop experience on iPad... | Read more »
The Walking Dead: No Man’s Land guide -...
A new update for The Walking Dead: No Man’s Land was released last week, making it the perfect time for you to head back to your base and take out some walkers. Here’s the lowdown on what’s new to the game, and how to take advantage. [Read more] | Read more »
Goat Rider guide - Tips and tricks to st...
We've all been there. One second, we're riding high on a crazed goat, and the next, we've been tossed off it like someone who's no good at goat ridin'. [Read more] | Read more »
Real Boxing 2 CREED: How to become a gre...
Just in time for Rocky fans who can’t wait to see CREED, the latest movie, we have the official tie-in game,Real Boxing 2 CREED. It builds on the success of its predecessor and there’s lots to take in so we at 148apps thought we’d run you through... | Read more »
CoinOp Heroes 2 guide - How to build an...
CoinOp Heroes 2 justlaunched and, like all clickers, it's dangerously addictive stuff. You have to furiously tap your screen to defeat wave after wave of foes and earn an insane amount of cash to spend on character upgrades and an army of minions... | Read more »
Dr. Panda Firefighters (Education)
Dr. Panda Firefighters 1.0.1 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0.1 (iTunes) Description: FIGHT FIRES AND SAVE THE DAY!Work together with Dr. Panda and his firefighting team to rescue his trapped... | Read more »
Puddle + (Games)
Puddle + 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Puddle is back in a new "+" edition featuring enhanced graphics, new videos and Apple TV support ! No IAP and No Ads. Dive into Puddle... | Read more »
Football Manager Mobile 2016 (Games)
Football Manager Mobile 2016 7.0.0 Device: iOS Universal Category: Games Price: $8.99, Version: 7.0.0 (iTunes) Description: Football Manager Mobile 2016 is designed to be played on the move and is the quickest way to manage your... | Read more »

Price Scanner via

Adorama Black Friday deals: Up to $400 off Ma...
Adorama has released their Black Friday deals for 2015. Save up to $400 on MacBook Pros, $200 on MacBooks and MacBook Airs, and $270 on iMacs. Use code RYBFDEAL during checkout to see these prices.... Read more
B&H Photo Deals: $200 off 12-inch 1.2GHz...
In addition to the B&H Photo Black Friday week sales we posted yesterday, B&H has lowered their price on two products to $200 off MSRP: - 12″ 1.2GHz Gray Retina MacBook: $1399 save $200 - 13... Read more
Best Buy Early Access: Today only, Up to $125...
Best Buy has iPad Air 2s on sale for up to $125 off MSRP and Apple Watch models on sale on their online store for up to $100 off MSRP with special codes through midnight CT tonight. Choose free... Read more
UPPERCASE DESIGNS Premium Ultra Thin Keyboard...
UPPERCASE Designs today announced its new Premium Ultra Thin Keyboard Protector and its Palm Rest Protector Set for the 12-inch MacBook. The accessories provide durable protection for the 12-inch... Read more
Al Jazeera Launches New iOS And Android Mobil...
Doha, Qatar based Al Jazeera has launched new mobile and tablet apps on the iOS and Android systems bringing the latest Al Jazeera news and programmes live together with on-demand personalisation.... Read more
B&H Photo Holiday Sale: Up to $250 off Ma...
B&H Photo has all new Macs on sale for up to $500 off MSRP as part of their Holiday sale including free shipping plus NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off - 15″ 2.... Read more
Free Aura ‘Ultimate’ Mac App For Gmail Update...
Miami, Florida based Crosscoded has announced Aura 1.2.0, an update to the Mac app for Gmail. Aura mixes the power of a native client with the flexibility of the Gmail web app with support for up to... Read more
Apple Will Edge Closer to Samsung in Smartpho...
Total smartphone shipments for 2015 are projected to decline by 9.7% to 1.286 billion units, according to the latest report from global market research firm TrendForce. Though Chinese vendors have... Read more
Sidefari – Split Screen Multitasking In Safar...
Francisco Cantu’s Sidefari is a simple web browser designed to act as a companion to Safari on the iPad. With multitasking in iOS 9, Sidefari uses the new Safari View Controller to show an extra... Read more
12-inch MacBooks in stock for up to $120 off,...
Adorama has 12″ Retina MacBooks in stock for up to $120 off MSRP including free shipping plus NY & NJ sales tax only. For a limited time, Adorama will include a free Apple USB-C to USB Adapter,... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Merchant Operations Manager: *Apple* Pay -...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
*Apple* Pay QA Manager - Apple Inc. (United...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
Sr Software Engineer *Apple* Pay - Apple In...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
Hardware Systems Architect - *Apple* Watch...
# Hardware Systems Architect - Apple Watch Job Number: 38449977 Santa Clara Valley, Califo ia, United States Posted: Apr. 16, 2015 Weekly Hours: **Job Summary** The Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.