Question

I created a simple program that takes the path of a directory as an input, creates an archive of that directory (converting it into a single file), adds a shebang to that file (so that the contents of the file can be easily extracted), and writes the file to the base directory of the specified path.

The problem is that the file does not extract itself when I double click on it. Instead the operating system (I’m using Ubuntu 11.10) tries to open it with gedit. This obviously shows the shebang, random gibberish, and the contents of the archived files.

I made the file executable, first by using chmod +x; and when it still didn’t work I tried chmod 777. However it still refuses to execute the file with the shebang when I double click on it. Perhaps this is because it’s not a pure text file.

Interestingly when I try to execute the file directly from command line it reads the shebang and extracts the contents of the archive properly. So there’s nothing wrong with my file format. I don’t know much about what operating systems do when you double click on a file but I would sure like to understand.

It surely makes no sense to add a shebang to a file if you still need to manually execute it from the command line. One advantage could be that you don’t need to specify the program to open it with but I believe that’s hardly an advantage. Any help will be greatly appreciated.

Update 1:

The program that creates the archive is called opm. It can be installed via the node package manager using the following command:

npm install opm

After that you simply use opm to pack and unpack directories for you. For example if I have a directory called test in my home directory then I can open a terminal and execute the following command to pack it:

opm test

This will create an archive of the directory called test.pack in the home directory. The .pack file has the shebang #!/usr/bin/opm. Opening a file with the extension .pack with opm tells it that it’s an archive and opm unpacks it in the same directory.

Note: Change the name of the test.pack file if you do not want it to overwrite your existing test directory.

I added the shebang to the .pack file so that it would extract itself when I opened it. However that doesn’t seem to work. Nevertheless if I run one of the following command then it works:

./test.pack

You may check my source code and make any modifications to the program as you may wish to.

Update 2:

Alright I created the following .desktop file for opm and stored it in the $HOME/.local/share/applications/ directory:

[Desktop Entry]
Type=Application
Version=1.0
Encoding=UTF-8
Name=OPM
GenericName=Object Packer and Minifier
NoDisplay=true
Comment=JavaScript Package Manager
TryExec=opm
Exec=opm %f
Terminal=false
MimeType=application/opm

Now I was able to associate .pack files with opm by right clicking on a .pack file, going to the Properties window, the Open With tab, and setting opm.desktop as the default application. Now I am able to unpack a .pack file by simply opening it.

However I would like to know how to associate .pack files with the mime type application/opm. Currently the .pack files are associated with application/x-java-pack200. How do I do so? Is it better if I use a different extension (e.g. .opm)? By associating the packed archives with the mime type application/opm will the OS open them with opm by default without having to explicitly set a default application from Properties > Open With?

Answer 1

If there’s already a MIME-type associated with .pack then you’ll want to use a different extension (.opm) to associate with your MIME-type (application/opm). The way you automatically associate a program that opens files of a specific MIME-type is with xdg-mime .

Alternatively,

• Edit ~/.local/share/applications/mimeapps.list and put your MIME/application combo under [Default Applications] like so:

[Default Applications]
application/opm=opm.desktop;

• Place your opm.desktop file in ~/.local/share/applications/ folder. (You’ve already done this)