Bash

The Bash shell is the foundation for the Opal framework. With version 3 of Opal, a scripting layer was added, designed to improve the experience of writing Bash scripts. In some cases, an opal function is just a friendly wrapper around native Bash behavior. In others, new functionality is added to enhance the user experience. Also, an effort was made to increase flexibility by providing XDG support.

This section of the Opal Documentation will describe the structure of the project and provide you with guidance on how to use the Opal framework. You’ll notice that Opal looks quite different from most shell scripts. Each of these functions uses the opal: prefix. This is to prevent collisions with other shell functions. The functions in the Opal framework are also coded defensively. Bash doesn’t natively support argument checking. So steps are taken to help guide you to pass the data directory. Bash natively separates strings on whitespace. So to maintain strings between functions you’ll need to quote them more heavily that in other programming languages.

Should you find yourself wishing that a Opal worked differently, don’t modify it. Instead, you should copy the function into your dotfiles and update the namespace to the string you use. The prefix dot: is recommended for your personal dotfiles. For example, the opal:data_dir function creates a path by using the output of opal:xdg_data_dir and appends the /opal subdirectory onto it. You should copy it and name your version dot:data_dir and update the logic to determine to which directory you want the data written.

Files

Bash uses two main configuration files - ~/.bashrc and ~/.bash_profile - to configure the user experience. Typically, the operating system will provide you with some minimal configuration. When Opal is installed, It will back up these files, and replace them with a more structured version that loads Opal as a dependency. Don’t panic! Your original is saved, and contains the current time in UNIX epoch seconds in the filename. It’s recommended that you copy anything you want to keep into your new configuration files.

Opal has a counterpart to each of the user configuration files.

bashrc.bash

The bashrc.bash file is read by your ~/.bashrc. It provides some suggested functionality to help improve your experience.. Upon install, when your ~/.bashrc is created, an “include” of this file is provided. Since this file is considered optional, you can choose to comment it out.

bash_profile.bash

This provides some environmental settings. This is where you’ll find some popular exported varibles like PATH, XDG_CONFIG_HOME, and EDITOR. The bash_profile.bash file is read by ~/.bash_profile

Organization

The majority of the Bash component is a collection of functions organized by subject. The functions use an opal: namespace, meaning each function name starts with it. This helps provide clarity, and prevents accidental redefinition of any existing functions. These functions can be used in bash scripts or directly on the command line. One essential function is opal:show takes a single parameter. Calling opal:show names will display a list of functions loaded in your shell.

$ opal:show names