Shell Integration
Overview
Shell integration covers the APIs and patterns for building tools that extend or interact with Unix shells. This includes completion systems, prompt hooks, key bindings, terminal control, and plugin distribution across Zsh, Bash, and Fish.
When to use: Building CLI tool completions, shell plugins, prompt customizations, terminal UI, dotfile managers, installation scripts, or native binary wrappers.
When NOT to use: General-purpose scripting unrelated to shell extension (use POSIX scripting reference for standalone scripts), GUI applications, or web server development.
Quick Reference
| Pattern | Shell | Key Points |
|---|---|---|
| Completion function | Zsh | compdef, compadd, zstyle for matcher configuration |
| Completion function | Bash | complete, compgen, COMP_WORDS, COMP_CWORD, COMPREPLY |
| Completion function | Fish | complete -c cmd -a args, condition flags, subcommand patterns |
| ZLE widget | Zsh | zle -N widget func, bindkey to map keys |
| Prompt hook | Zsh | precmd, preexec, chpwd via add-zsh-hook |
| Prompt hook | Bash | PROMPT_COMMAND (string or array in Bash 5.1+) |
| Event handler | Fish | --on-event, --on-variable, --on-signal |
| Abbreviation | Fish | abbr -a name expansion, --function for dynamic |
| Parameter expansion | Zsh | ${(s.:.)var}, ${var:=default}, flags and modifiers |
| Terminal control | All | ANSI/CSI escape sequences, tput, stty |
| Signal handling | All | trap builtin, cleanup patterns, EXIT/INT/TERM |
| Process management | All | Job control (&, wait, bg, fg), subshells, coprocesses |
| Plugin installation | All | Sourcing strategies, version detection, ZDOTDIR loading order |
Common Mistakes
| Mistake | Correct Pattern |
|---|---|
Using echo -e for escape sequences portably | Use printf or tput for portability across shells and OSes |
Modifying PROMPT_COMMAND with = in Bash | Append with += to avoid overwriting other tools |
| Defining Fish event handlers in lazy-loaded functions | Place event handlers in config.fish or source them explicitly |
| Hardcoding terminal capabilities | Query via tput which respects TERM and terminfo |
Missing emulate -L zsh in Zsh functions | Always set local options to avoid polluting caller environment |
Using $COMP_LINE splitting instead of COMP_WORDS | Use COMP_WORDS[$COMP_CWORD] for reliable word extraction |
Not quoting $@ in wrapper scripts | Always use "$@" to preserve argument boundaries |
Assuming /bin/sh is Bash | Target POSIX sh for portable scripts, test with dash |
Using function keyword in POSIX scripts | Use name() {...} syntax for POSIX compatibility |
Ignoring EXIT trap for cleanup | Always set trap cleanup EXIT for temp files and state |
Delegation
- Completion testing: Use
Exploreagent to verify completions interactively - Script review: Use
Taskagent for cross-shell compatibility audits - Code review: Delegate to
code-revieweragent
If therustskill is available, delegate native binary compilation patterns to it. Shell wrappers often invoke Rust-compiled binaries for performance-critical operations. If thecli-power-toolsskill is available, delegate modern CLI utility patterns to it. Many shell plugins wrap tools likefd,ripgrep, andfzf.
References
- Zsh integration: ZLE, completions, hooks, parameter expansion
- Bash integration: readline, completions, PROMPT_COMMAND, shopt
- Fish integration: completions, events, abbreviations, functions
- Terminal control: ANSI/CSI sequences, tput, stty, capabilities
- POSIX scripting: portable patterns, signal handling, process management
- Plugin distribution: installation scripts, dotfile management, version detection