repl

js/cli/repl.md

Bare fino and fino repl start an interactive runtime session. Use the REPL for quick checks against runtime APIs, small import experiments, and debugging snippets that are not yet worth turning into a script or test:

fino repl

The parent realm owns terminal input and output. Evaluation runs in a child realm through the inspector bridge, so user code executes in a normal runtime context instead of mutating the root CLI module. That keeps the CLI shell separate from the code being evaluated while still giving snippets access to the same runtime modules they would have in a script.

Command Reference

Behavior

The REPL supports top-level await, simple multiline input through bracket and quote balancing, expression result printing, and exits on .exit, Ctrl-C, Ctrl-D, or stdin EOF. Thrown errors are printed without ending the session.

Typical REPL work should stay exploratory:

> const { readFile } = await import('fino:file/fs')
> await readFile('package.json')

This is not Node's repl module. There is no persistent history file, completion API, raw terminal editing contract, pluggable writer, or PTY-specific behavior guarantee yet. Embedded realm REPL mode is limited to same-process realms; repl: true is rejected with thread, process, remote, or watch.