How to use the command 'elvish' (with examples)

Elvish is an expressive programming language that also functions as a powerful and versatile interactive shell. It combines the functionalities of a traditional shell with the expressiveness of modern programming languages, enabling users to write scripts and execute shell commands efficiently. Elvish is designed to enhance the interactive experience through features like job control, autocomplete, and a rich set of built-in commands. Its syntax and semantics facilitate more readable and maintainable scripts compared to many other shell languages. Below, we explore various use cases demonstrating the command execution in Elvish.

Use case 1: Start an interactive shell session

Code:

elvish

Motivation for using this example:

Starting an interactive shell session is one of the fundamental actions to take when working with Elvish. This allows users to enter commands directly and interact with the shell, making it ideal for running commands ad hoc or testing small scripts before they are compiled into larger scripts. This mode supports numerous features for facilitating your work like command history, suggestion, and piping outputs directly between commands without manually redirecting output files.

Explanation:

• elvish: Invoking the elvish command without any options or arguments starts an interactive Elvish shell session. This means you are greeted with a prompt where you can type further commands or execute scripts directly within the shell environment.

Example output:

When you start an interactive shell session, you will receive a new prompt similar to:

~> 

This prompt indicates that you can now enter commands.

Use case 2: Execute specific [c]ommands

Code:

elvish -c "echo 'elvish is executed'"

Motivation for using this example:

Executing specific commands through Elvish is particularly useful for scripts or automation tasks where you need to run a single command efficiently without entering an interactive session. This is commonly used for one-off tasks or when you want the output of a command directly available in your script without additional user interaction.

Explanation:

• elvish: This invokes the Elvish shell.
• -c: This option is used to specify that what follows is a command to be executed. The -c stands for command.
• "echo 'elvish is executed'": This is the specific command that the Elvish shell will execute. Here, echo is a command that outputs the string ’elvish is executed’ to the terminal.

Example output:

If the command executes successfully, you should see:

elvish is executed

This output indicates that the command was carried out and the specified string was printed to the terminal.

Use case 3: Execute a specific script

Code:

elvish path/to/script.elv

Motivation for using this example:

Running scripts directly is a cornerstone of utilizing Elvish efficiently, as it allows the user to execute prewritten scripts that can perform complex and repeated tasks without entering commands manually each time. This is crucial for automation, facilitating workflows, and managing system tasks that have been encapsulated within scripts.

Explanation:

• elvish: This invokes the Elvish shell.
• path/to/script.elv: This is the path to the script you want the Elvish shell to execute. The file should contain Elvish commands and have appropriate permissions to be executed. The .elv extension typically signifies an Elvish script file, although it can be any text file containing valid Elvish commands.

Example output:

Assume that path/to/script.elv contains the following Elvish code:

echo 'Executing the script file'

When executed, the output should be:

Executing the script file

This confirms that the script ran successfully, and its contents were executed as expected.

Conclusion:

Understanding how to utilize the Elvish command in its various forms is essential for effectively leveraging its capabilities, whether you’re working interactively, running specific commands, or executing scripts. Elvish provides a flexible and powerful environment for shell scripting and command execution, fostering efficient workflow and automation in modern computing tasks.