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

Latest Forum Discussions

See All

Top Mobile Game Discounts
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links... | Read more »
Price of Glory unleashes its 1.4 Alpha u...
As much as we all probably dislike Maths as a subject, we do have to hand it to geometry for giving us the good old Hexgrid, home of some of the best strategy games. One such example, Price of Glory, has dropped its 1.4 Alpha update, stocked full... | Read more »
The SLC 2025 kicks off this month to cro...
Ever since the Solo Leveling: Arise Championship 2025 was announced, I have been looking forward to it. The promotional clip they released a month or two back showed crowds going absolutely nuts for the previous competitions, so imagine the... | Read more »
Dive into some early Magicpunk fun as Cr...
Excellent news for fans of steampunk and magic; the Precursor Test for Magicpunk MMORPG Crystal of Atlan opens today. This rather fancy way of saying beta test will remain open until March 5th and is available for PC - boo - and Android devices -... | Read more »
Prepare to get your mind melted as Evang...
If you are a fan of sci-fi shooters and incredibly weird, mind-bending anime series, then you are in for a treat, as Goddess of Victory: Nikke is gearing up for its second collaboration with Evangelion. We were also treated to an upcoming... | Read more »
Square Enix gives with one hand and slap...
We have something of a mixed bag coming over from Square Enix HQ today. Two of their mobile games are revelling in life with new events keeping them alive, whilst another has been thrown onto the ever-growing discard pile Square is building. I... | Read more »
Let the world burn as you have some fest...
It is time to leave the world burning once again as you take a much-needed break from that whole “hero” lark and enjoy some celebrations in Genshin Impact. Version 5.4, Moonlight Amidst Dreams, will see you in Inazuma to attend the Mikawa Flower... | Read more »
Full Moon Over the Abyssal Sea lands on...
Aether Gazer has announced its latest major update, and it is one of the loveliest event names I have ever heard. Full Moon Over the Abyssal Sea is an amazing name, and it comes loaded with two side stories, a new S-grade Modifier, and some fancy... | Read more »
Open your own eatery for all the forest...
Very important question; when you read the title Zoo Restaurant, do you also immediately think of running a restaurant in which you cook Zoo animals as the course? I will just assume yes. Anyway, come June 23rd we will all be able to start up our... | Read more »
Crystal of Atlan opens registration for...
Nuverse was prominently featured in the last month for all the wrong reasons with the USA TikTok debacle, but now it is putting all that behind it and preparing for the Crystal of Atlan beta test. Taking place between February 18th and March 5th,... | Read more »

Price Scanner via MacPrices.net

AT&T is offering a 65% discount on the ne...
AT&T is offering the new iPhone 16e for up to 65% off their monthly finance fee with 36-months of service. No trade-in is required. Discount is applied via monthly bill credits over the 36 month... Read more
Use this code to get a free iPhone 13 at Visi...
For a limited time, use code SWEETDEAL to get a free 128GB iPhone 13 Visible, Verizon’s low-cost wireless cell service, Visible. Deal is valid when you purchase the Visible+ annual plan. Free... Read more
M4 Mac minis on sale for $50-$80 off MSRP at...
B&H Photo has M4 Mac minis in stock and on sale right now for $50 to $80 off Apple’s MSRP, each including free 1-2 day shipping to most US addresses: – M4 Mac mini (16GB/256GB): $549, $50 off... Read more
Buy an iPhone 16 at Boost Mobile and get one...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering one year of free Unlimited service with the purchase of any iPhone 16. Purchase the iPhone at standard MSRP, and then choose... Read more
Get an iPhone 15 for only $299 at Boost Mobil...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering the 128GB iPhone 15 for $299.99 including service with their Unlimited Premium plan (50GB of premium data, $60/month), or $20... Read more
Unreal Mobile is offering $100 off any new iP...
Unreal Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering a $100 discount on any new iPhone with service. This includes new iPhone 16 models as well as iPhone 15, 14, 13, and SE... Read more
Apple drops prices on clearance iPhone 14 mod...
With today’s introduction of the new iPhone 16e, Apple has discontinued the iPhone 14, 14 Pro, and SE. In response, Apple has dropped prices on unlocked, Certified Refurbished, iPhone 14 models to a... Read more
B&H has 16-inch M4 Max MacBook Pros on sa...
B&H Photo is offering a $360-$410 discount on new 16-inch MacBook Pros with M4 Max CPUs right now. B&H offers free 1-2 day shipping to most US addresses: – 16″ M4 Max MacBook Pro (36GB/1TB/... Read more
Amazon is offering a $100 discount on the M4...
Amazon has the M4 Pro Mac mini discounted $100 off MSRP right now. Shipping is free. Their price is the lowest currently available for this popular mini: – Mac mini M4 Pro (24GB/512GB): $1299, $100... Read more
B&H continues to offer $150-$220 discount...
B&H Photo has 14-inch M4 MacBook Pros on sale for $150-$220 off MSRP. B&H offers free 1-2 day shipping to most US addresses: – 14″ M4 MacBook Pro (16GB/512GB): $1449, $150 off MSRP – 14″ M4... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.