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

TinkerTool 5.4 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Tinderbox 6.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
Parallels Desktop 10.2.2 - Run Windows a...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
Adobe Premiere Pro CC 2015 9.0.1 - Digit...
Premiere Pro CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Premiere Pro customer). Premiere Pro CS6 is still available for... Read more
Adobe After Effects CC 2015 13.5.1 - Cre...
After Effects CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). After Effects CS6 is still available... Read more
Adobe Creative Cloud 2.2.0.129 - Access...
Adobe Creative Cloud costs $49.99/month (or less if you're a previous Creative Suite customer). Creative Suite 6 is still available for purchase (without a monthly plan) if you prefer. Introducing... Read more
Tower 2.2.3 - Version control with Git m...
Tower is a powerful Git client for OS X that makes using Git easy and more efficient. Users benefit from its elegant and comprehensive interface and a feature set that lets them enjoy the full power... Read more
Apple Java 2015-001 - For OS X 10.7, 10....
Apple Java for OS X 2015-001 installs the legacy Java 6 runtime for OS X 10.11 El Capitan, OS X 10.10 Yosemite, OS X 10.9 Mavericks, OS X 10.8 Mountain Lion, and OS X 10.7 Lion. This package is... Read more
Adobe Muse CC 2015 2015.0.1 - Design and...
Muse CC 2015 is available as part of Adobe Creative Cloud for as little as $14.99/month (or $9.99/month if you're a previous Muse customer). Muse CS6 is still available for purchase (without a... Read more
Adobe Illustrator CC 2015 19.1.0 - Profe...
Illustrator CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Illustrator customer). Illustrator CS6 is still available for... Read more

This Week at 148Apps: July 20-24, 2015
July is Heating Up With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »
Red Game Without A Great Name (Games)
Red Game Without A Great Name 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: The mechanical bird is flying through an unfriendly, Steampunk world. Help it avoid obstacles and deadly... | Read more »
Warhammer: Arcane Magic (Games)
Warhammer: Arcane Magic 1.0.2 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0.2 (iTunes) Description: Engage in epic battles and tactical gameplay that challenge both novice and veteran in Warhammer: Arcane Magic, a... | Read more »
Mazes of Karradash (Games)
Mazes of Karradash 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The city of Karradash is under attack: the monsters of the Shadow Realms are emerging from the depths.No adventurer is... | Read more »
Battle Golf is the Newest Game from the...
Wrassling was a pretty weird - and equally great - little wressling game. Now the developers, Folmer Kelly and Colin Lane, have turned their attention to a different sport: golfing. This is gonna be weird. [Read more] | Read more »
Qbert Rebooted has the App Store Going...
The weird little orange... whatever... is back, mostly thanks to that movie which shall remain nameless (you know the one). But anyway it's been "rebooted" and now you can play the fancy-looking Qbert Rebooted on iOS devices. [Read more] | Read more »
Giant Monsters Run Amok in The Sandbox...
So The Sandbox has just hit version number 1.99987 (seriously), and it's added a lot more stuff. Just like every other update, really. [Read more] | Read more »
Fish Pond Park (Games)
Fish Pond Park 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: Nurture an idyllic slice of tourist's heaven into the top nature spot of the nation, furnishing it with a variety of... | Read more »
Look after Baby Buddy on your Apple Watc...
Parigami Gold is the new premium version of the match three puzzler that includes Apple Watch support and all new content. You won't simply be sliding tiles around on your wrist, the Apple Watch companion app is an all new mini-game in itself. You'... | Read more »
Swallow all of your opponents as the big...
Eat all of the opposition and become the largest ball in Battle of Balls now available in the App Store and Google Play. Battle of Balls pits you against other opponents in real time and challenges you to eat more balls and grow larger than all of... | Read more »

Price Scanner via MacPrices.net

Sale! 13″ 1.6GHz/256GB MacBook Air for $1099,...
B&H Photo has the 13″ 1.6GHz/256GB MacBook Air on sale for $1099 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model. Read more
iPad mini 4 To Be Upgraded To iPad Air 2 Spec...
There’s a certain inevitability about making Apple product predictions this time of year. Come September, we can pretty reliably count on the release of refreshed iPhones, along with the iOS 9... Read more
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 2.5GHz MacBook Pro on sale for $899,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $899.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $200 off MSRP. Price is... Read more
21-inch 2.9GHz iMac on sale for $1299, save $...
Best Buy has the 21″ 2.9GHz iMac on sale today for $1299.99 on their online store. Choose free shipping or free local store pickup (if available). Their price is $200 off MSRP, and it’s the lowest... Read more
Free Image Sizer 1.3 for iOS Offers Photo Edi...
Xi’An, China based G-Power has announced the release of Image Sizer 1.3 for the iPhone, iPad, and iPod touch, an important update to their free photo editing app. Image Sizer’s collection of easy to... Read more
Sale! 13″ 1.6GHz/128GB MacBook Air for $899,...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model. Read more
13-inch Retina MacBook Pros on sale for $100...
Best Buy has 13-inch Retina MacBook Pros on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Prices are for online orders only, in-store... Read more
Will BMW’s i3 Electric Vehicle Be The Automo...
The German-language business journal Manager Magazin’s Michael Freitag reports that Apple and the German performance/luxury automaker Bayerishe Motoren Werke (BMW) are back at far-reaching... Read more
Sale! $250 off 15-inch Retina MacBook Pro, $2...
B&H Photo has lowered their price for the 15″ 2.2GHz Retina MacBook Pro to $1749, or $250 off MSRP. Shipping is free, and B&H charges NY sales tax only. They have the 27″ 3.3GHz 5K iMac on... Read more

Jobs Board

*Apple* Customer Experience (ACE) Leader - A...
…management to deliver on business objectives Training partner store staff on Apple products, services, and merchandising guidelines Coaching partner store staff on Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
*Apple* TV Product Design Internship (Spring...
…the mechanical design effort associated with creating world-class products with the Apple TV PD Group. Responsibilities will include working closely with manufacturing, Read more
*Apple* Watch SW Application Project Manager...
**Job Summary** The Apple Watch software team is looking for an Application Engineering Project Manager to work on new projects for Apple . The successful candidate Read more
*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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.