Perl droplets for Mac OS X

The editor that came with MacOS Perl (for Mac OS 9 and below) was able to save your script as a droplet -- that is, an application that you could run by dropping files onto it. When your script got control, the paths to the dropped files were in @ARGV

Under Mac OS X you can get this functionality by wrapping your Perl script in an Apple Script. The following example assumes you want to wrap a Perl script named droplet.PL in an application called PerlDroplet. It works because a Mac OS X application bundle is simply a directory whose contents are known to the system.

  1. Run the Script Editor, which is found in /Applications/AppleScript/
  2. Paste the text of the Apple Script as it appears below into the editor.
  3. Save the script as an Application Bundle named PerlDroplet.
  4. Copy your Perl script to directory

Yes, this will work if you move PerlDroplet somewhere else.

The 'do shell script' directive used to get the Perl script to run will actually work on any command that /bin/sh can handle. This means you need a shebang line in your script, or you need to explicitly run Perl. The do shell script is the equivalent of Perl's back tick or qx{} operators; anything the command writes to standard out is returned to the Apple Script.

The environment your script sees is fairly minimal. Specifically, you will not see anything you defined in your .profile or .bash_profile file. You will, however, see anything you define in ~/.MacOSX/environment.plist -- that is, once you log out and log back in again. Restarting the finder is not sufficient.

OK, at long last here is the actual Apple Script. The blogging software truncates it on the right, but it turns out that if you select everything and do a Copy, the un-truncated text ends up in the paste buffer, at least using Firefox 3.6.24 under Mac OS 10.5.8 Leopard.

-- field the drop event
on open argv

-- Make the file names into strings containing quoted POSIX file names, and concatenate them with spaces between.
set shell_argv to ""
repeat with arg in argv
set shell_argv to shell_argv & " " & quoted form of POSIX path of arg
end repeat

-- Our Perl script is droplet.PL in the Resources directory of the application bundle.
set perl_script to quoted form of POSIX path of (path to resource "droplet.PL")

-- Run the Perl script. The file names appear in @ARGV. Its output to STDOUT is captured in result.
set result to do shell script perl_script & shell_argv

-- Display a dialog containing the result.
display dialog result as string

end open

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About Tom Wyant

user-pic I blog about Perl.