Fish (Friendly Interactive Shell)

Fish v4.0 (2025) is rewritten in Rust. It is famous for “It just works” – 90% of what you need (autosuggestions, coloring) is enabled by default.

When to Use

• Interactive Use: It is arguably the best shell for typing commands manually.
• Discoverability: Man page completions are generated automatically.

Core Concepts

Autosuggestions

Fish suggests commands as you type based on history and completions. Right arrow accepts.

Universal Variables

set -U my_var value sets a variable across all current and future shell instances instantly.

Web Config

fish_config launches a browser UI to change colors and prompt.

Best Practices (2025)

Do:

• Use it as Interactive Shell: Set it as your login shell.
• Don’t write scripts in Fish: Write scripts in bash or sh for portability. Run them from Fish.
• Use “Fisher”: The plugin manager for themes.

Don’t:

• Don’t copy-paste Bash: Fish syntax is different (env var=val -> set -x var val).

References

• Fish Shell Documentation