Launching your application¶

Command line¶

Most applications on Linux can be launched from the command line, even if they don’t show output in the terminal. To allow this, you need an executable file in any of the directories listed in the PATH environment variable. These will often end in bin, such as /usr/local/bin.

Executable files

On Unix, an executable file is one with the ‘execute bit’ set in its permissions. You can make a file executable with this command:

chmod +x path/to/file

The file should be either a compiled ‘binary’, or a text script. Scripts need to start with a ‘shebang’, a line that identifies the interpreter to run the script with. For example:

#!/usr/bin/python3

The command is the filename. By convention, it should be lower case. If you want to use more than one word, separate them with hyphens, e.g. chromium-browser.

Desktop launcher¶

To add your application to the desktop launcher or applications menu, you need a desktop entry file, with a .desktop extension. It contains something like this:

[Desktop Entry]
Version=1.0
Type=Application

# The name will be displayed
Name=Inkscape
# Translations are possible: they're used depending on the system locale
Name[hi]=इंकस्केप

# See the icon section for how this is looked up.
Icon=inkscape

# The command to launch your application. %F is for file paths to open.
Exec=inkscape %F

# File types it can open; see file associations.
MimeType=image/svg+xml;...

Your application’s desktop entry is also used for file association.

There are a number of other optional fields you can use. See the links below for more information.

These desktop files are placed in an applications subdirectory of each XDG data directory. If you have to put it in place yourself, the normal locations are:

Per-user: ~/.local/share/applications
System: /usr/local/share/applications

File associations¶

To use your application for opening files from the file manager, specify the details in your desktop file. In the Exec field, make sure your launch command includes a placeholder like %F:

Exec=inkscape %F

%F may be replaced by one or more file paths. Use lowercase %f if it can only handle one path per command. %U and %u are similar, but they pass URLs. Local files have URLs starting file://, but the platform might also pass HTTP or FTP URLs to your application.

Then use the MimeType field to specify what MIME types it handles:

MimeType=image/svg+xml;image/x-eps;

There may be other applications that support the same MIME type. It’s normally up to the user to pick the default application for a file type, but if you have a good reason to change it, you can use a mimeapps.list file as described in the MIME associations specification.

Define a MIME type¶

A MIME type is meant to be a unique name for a file format, like image/png or text/x-makefile. For new MIME types, the recommended format is application/vnd.org_name.app_name, filling in the organisation name and app or format name as appropriate (e.g. Libreoffice ODT files are application/vnd.oasis.opendocument.text). You can add +json or +xml to the end if your file format is based on one of these generic data formats.

MIME types are added to the system with XML files like this:

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
  <mime-type type="application/vnd.acme.frobulate">
      <comment>Frobulate file</comment>
      <glob pattern="*.frobulate"/>
  </mime-type>
</mime-info>

The <glob> tag specifies a file extension for files with this MIME type. Other fields can distinguish different file types sharing the same extension, but it’s best to pick a unique extension. There’s no need to limit the extension to three letters.

The filename of this XML file should start with the vendor name, e.g. acme-frobulate.xml. Call xdg-mime install acme-frobulate.xml to install it. This will copy it into a directory such as /usr/local/share/mime/packages, and rebuild the MIME database from all of these XML source files.