How to Use the Command 'rustup completions' (with examples)

The rustup completions command is a useful tool for generating shell completion scripts for Rust’s toolchains, specifically rustup and cargo. These completion scripts help improve the user experience by providing features like auto-completion of commands and options in multiple shell environments, such as Bash, Zsh, Fish, Powershell, and Elvish. The availability of such features smoothens the workflow and reduces errors when typing commands in the terminal.

Use Case 1: Print the Completion Script to stdout

Code:

rustup completions bash rustup

Motivation:

Imagine you are a Rust developer who frequently uses rustup to manage Rust versions and toolchains, and you are working in a Bash shell environment. Auto-completion can save you a lot of time and keystrokes. By generating the completion script for Bash, you can activate auto-completion every time you use rustup. This capability enhances your workflow by allowing you to quickly navigate through possible command options and subcommands, reducing the likelihood of typing errors and remembering complex command syntax.

Explanation:

• rustup completions: The primary command used to generate completion scripts.
• bash: Specifies the target shell environment for which you want to generate the completion script.
• rustup: Indicates that the completion script should be generated for the rustup command, providing auto-completion for its commands and options.

Example Output:

The execution of the above command does not immediately alter shell behavior. It simply outputs a configuration script to the terminal. The script is intended to be sourced, typically by adding it to a file like .bashrc or .bash_profile, activating the completion feature on the next shell session. The script contains a series of Bash function definitions and configuration lines specific to rustup completions.

For example:

# bash completion script
complete -o default -o nospace -F _rustup rustup

Use Case 2: Print the Completion Script for cargo in Zsh

Code:

rustup completions zsh cargo

Motivation:

Suppose you are a Rust programmer who prefers using the Zsh shell, renowned for its extensibility and user-friendly features. You frequently work with cargo, the Rust package manager, to manage and build your projects. Having a completion script will enhance your productivity by suggesting relevant cargo subcommands, flags, and arguments as you type. This feature reduces the time spent recalling command syntax and allows for a more seamless programming experience.

Explanation:

• rustup completions: The base command is responsible for generating shell-specific completion scripts.
• zsh: Specifies the Zsh shell, ensuring that the generated script is compatible with Zsh syntax and conventions.
• cargo: Specifies that the completion script to be generated is for cargo, thereby providing necessary completions for cargo-related commands within the Zsh shell environment.

Example Output:

The output of the command is a Zsh-compatible script possessing the capability to enhance the command-line interface through intelligent completions. This script typically needs to be sourced or linked to a location recognized by Zsh, such as ~/.zshrc, allowing cargo to support tab completion features.

Example script output comes in a format like below:

#compdef cargo
_cargo() {
  (...)
  # functions and scripts for completions
}

Conclusion:

Using rustup completions is a strategic way to integrate command-line enhancements into your daily workflow as a Rust programmer. Generating and utilizing these scripts can significantly reduce typing effort, minimize command-related errors, and increase overall efficiency when using rustup and cargo with supported shells. By choosing the appropriate shell environment and target command, one can tailor their development experience to be as smooth and error-free as possible.