Shell Builtins
Use when creating a new shell builtin command for Crush (internal/shell/), editing an...
Install
npx skills add charmbracelet/crush --skill shell-builtins -g -a claude-code -y- Repository
- charmbracelet/crush28.9k
- Category
- Engineering
- Updated
- 3d ago
- License
- See repository
- Context cost
- Lightabout 731 tokens
- Runs scripts
- No, instructions only
What it does
Use when creating a new shell builtin command for Crush (internal/shell/), editing an existing one, or when the user needs to understand how commands are intercepted in Crush's embedded shell.
Shell Builtins
Crush's shell (internal/shell/) uses mvdan.cc/sh/v3 for POSIX shell
emulation. Commands can be intercepted before they reach the OS by adding
builtins, functions handled in-process.
How Builtins Work
Builtins live in builtinHandler() in internal/shell/run.go. This is an
interp.ExecHandlerFunc middleware registered in standardHandlers()
before the block handler, so builtins run even for commands that would
otherwise be blocked. The same handler chain is shared by the stateful
Shell type and the stateless Run entrypoint used by the hook runner,
so builtins are available identically in the bash tool and in hooks.
The handler is a switch on args[0]. Each case either handles the command
inline or delegates to a helper function.
