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

Ableton Live 9.7.1 - Record music using...
Ableton Live lets you create and record music on your Mac. Use digital instruments, pre-recorded sounds, and sampled loops to arrange, produce, and perform your music like never before. Ableton Live... Read more
FileZilla 3.23.0.2 - Fast and reliable F...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.23.0.2: Bug Fixes and Minor Changes Speed up icon... Read more
Vivaldi 1.5.658.56 - An advanced browser...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more
Safari Technology Preview 10.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more
TunnelBear 3.0.8 - Subscription-based pr...
TunnelBear is a subscription-based virtual private network (VPN) service and companion app, enabling you to browse the internet privately and securely. Features Browse privately - Secure your data... Read more
NeoFinder 7.0 - Catalog your external me...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more
Coda 2.6 - One-window Web development su...
Coda is a powerful Web editor that puts everything in one place. An editor. Terminal. CSS. Files. With Coda 2, we went beyond expectations. With loads of new, much-requested features, a few surprises... Read more
File Juicer 4.51 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. In computer... Read more
PDFpenPro 8.3 - $124.95
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Create fillable forms and tables of content... Read more
PDFpen 8.3 - $74.95
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more

Latest Forum Discussions

See All

Clash of Clans is getting its own animat...
Riding on its unending wave of fame and success, Clash of Clans is getting an animated web series based on its Clash-A-Rama animated shorts.As opposed to the current shorts' 60 second run time, the new and improved Clash-A-Rama will be comprised of... | Read more »
Leaks hint at Pokémon GO and Starbucks C...
Leaked images from a hub for Starbucks employees suggests that a big Pokémon GO event with the coffee giant could begin this very week. The images appeared on Reddit and hint at some exciting new things to come for Niantic's smash hit game. | Read more »
Silent Depth Submarine Simulation (Game...
Silent Depth Submarine Simulation 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: | Read more »
Enneas Saga lets you lead your own demon...
Defend the land of Enneas Continent from the forces of evil in the new fantasy MMORPG from Lyto Mobi: Enneas Saga. Can’t wait? No problem. It’s available to download now on Android devices. | Read more »
Great zombie games in the spirit of Dead...
Dead Rising 4 arrives tomorrow, giving enthusiasts a fresh chance to take selfies with zombies and get up to other ridiculous end-of-the-world shenanigans. To really get into the spirit of things, we've gone and gathered the best zombie games that... | Read more »
Amateur Surgeon 4 Guide: Advanced tips a...
Amateur Surgeon 4 is still tackling the competition at the top of the App Store charts, so if you haven't tried it out yet, you should probably do that right away. If you've been at it for a while, though, perhaps you're ready to start expanding... | Read more »
Amateur Surgeon 4 Guide: Become the worl...
It's time to wield your trusty pizza cutter again, as Amateur Surgeon has returned with a whole fresh set of challenges (and some old, familiar ones, too). Starting anew isn't easy, especially when all you have at your disposal is a lighter, the... | Read more »
Le Parker: Sous Chef Extraordinaire (Ga...
Le Parker: Sous Chef Extraordinaire 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Telltale Games really is working on a Gu...
Telltale Games' next episodic adventure is indeed Guardians of the Galaxy. A document tied to the voice actors strike suggested that the project was in the work, but now we have direct confirmation following an announcement at the Game Awards that... | Read more »
Amateur Surgeon returns to iOS and Andro...
Amateur Surgeon and its two sequels disappeared from the App Store some time and it was sad days for all. But now, just in time for the holidays, the Adult Swim favorite makes its joyous return in the shape of Amateur Surgeon 4, a remake with... | Read more »

Price Scanner via MacPrices.net

Twenty-Five Years Of Apple Laptops – A person...
Among many other things, the often tumultuous 16th year of the new century marked the 25th anniversary of Apple laptop computers, not counting the optimistically named 16-pound Mac Portable of 1989.... Read more
Landlordy iOS App Adds Support For Appliances...
Riga, Latvia based E-protect SIA is releasing major update (version 1.8) to its Landlordy app for managing rental business financials on the go. Landlordy is iPhone and iPad app designed for self-... Read more
Holiday sale, Apple iMacs for up to $200 off...
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $... Read more
Holiday sale: Mac minis for $50 to $100 off M...
B&H Photo has Mac minis on sale for up to $100 off MSRP free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $629 $70 off MSRP - 2.8GHz Mac mini: $899 $... Read more
Mac Pros on sale for up to $300 off MSRP, ref...
B&H Photo has Mac Pros on sale for up to $300 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3699, $... Read more
12-inch WiFi Apple iPad Pros on sale for up t...
B&H Photo has 12″ WiFi Apple iPad Pros on sale for up to $50 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off MSRP... Read more
9-inch Apple WiFi iPad Pros on sale for $20-$...
B&H Photo has 9.7″ Apple WiFi iPad Pros on sale for $20-$50 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 256GB WiFi iPad Pro: $779.95 $20 off MSRP... Read more
Apple refurbished 2015 15-inch MacBook Pros a...
Apple has Certified Refurbished 2015 15″ Retina MacBook Pros available starting at $1699. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2.2GHz Retina MacBook Pro... Read more
Back in stock! 13-inch 2.7GHz Retina MacBook...
Apple has Apple Certified Refurbished 2015 13″ 2.7GHz/128GB Retina MacBook Pros (MF839LL/A) available again for $1099 including free shipping. That’s $200 off MSRP, and it’s the lowest price... Read more
Slate Tablet Market Share to Fall Below 75% i...
After two years of decline, the tablet market is showing signs of new life as productivity trumps entertainment, and tablets become cost-effective computing devices for both entertainment and... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Philade...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- San Ant...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Products Tester Needed - Apple (Unit...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
SW Engineer *Apple* TV Frameworks - Apple I...
The Apple TV team is looking for a software...create features that reflect the look and feel of Apple TV. Description: Were looking for someone who is Read more
Hardware Design Validation Engineer - *Apple...
The Apple Watch team is looking for a Hardware Design Validation Engineer. This person will be part of the Apple Watch hardware team with responsibilities for Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.