Setting Environment Variables in .desktop Files in Ubuntu

In this article, we will discuss how to set environment variables in .desktop files in Ubuntu. This is a useful technique for customizing the behavior of applications on a per-user basis.

Understanding .desktop Files

Before we dive into the specifics, let’s first understand what .desktop files are. These are essentially shortcuts that are used to launch applications in Linux. They contain information about an application such as its name, icon, and the command to run it. You can find these files in /usr/share/applications/ for system-wide applications or ~/.local/share/applications/ for user-specific applications.

Setting Environment Variables Using the env Command

One of the ways to set environment variables in a .desktop file is by using the env command. This command allows you to modify the environment for command invocations. It can be used to set one or more environment variables right before a command in a shell.

Let’s take an example where we want to set the GTK2_RC_FILES variable to gtkrc.custom and run eclipse. We can modify the Exec line in the .desktop file as follows:

Exec=env GTK2_RC_FILES=gtkrc.custom /path/to/eclipse

In this command, env is the command that sets the environment variable. GTK2_RC_FILES is the name of the environment variable we want to set, and gtkrc.custom is the value we want to assign to this variable. /path/to/eclipse is the command we want to run after setting the environment variable.

Using a Wrapper Script

Another approach to set environment variables in a .desktop file is by creating a wrapper script. This script will set the environment variable and then run the application.

Here’s how you can create a wrapper script:

1. Create a script (e.g., eclipse.sh) with the following content:

#!/bin/sh
export GTK2_RC_FILES=gtkrc.custom
exec /path/to/eclipse "$@"

In this script, export is a command that sets the environment variable. GTK2_RC_FILES is the name of the environment variable we want to set, and gtkrc.custom is the value we want to assign to this variable. /path/to/eclipse "$@" is the command we want to run after setting the environment variable. The "$@" part ensures that all arguments passed to the script will be forwarded to the eclipse command.

2. Make the script executable by running the following command:

chmod +x eclipse.sh

3. In the .desktop file, set the Exec line to:

Exec=/path/to/eclipse.sh

This way, the customization won’t be overwritten when the application package is updated.

Setting Environment Variables Containing the User’s Home Directory

If you want to set an environment variable containing the user’s home directory, you can use the ~ symbol in the .desktop file. For example:

Exec=env MYVAR="~/foo"

However, it’s important to note that the ~ symbol won’t be expanded in the Exec line. Instead, it will be passed literally. To expand the ~ symbol, you can use a wrapper script or follow the approach mentioned in this Stack Overflow post.

Conclusion

Setting environment variables in .desktop files in Ubuntu allows you to customize the behavior of applications on a per-user basis. You can do this by using the env command in the Exec line or by creating a wrapper script. Both approaches are effective and can be used depending on your specific needs.