REPL

The repl command starts an interactive FQL shell where you can type expressions and see results immediately.

$ferret repl

The shell prints a version banner and presents a > prompt:

Welcome to Ferret REPL 2.0.0-alpha.57
Please use `exit` or `Ctrl-D` to exit this program.
>

Evaluate expressions

Type any FQL expression at the prompt. The result prints as soon as evaluation finishes:

> return 1 + 2
3

> return { name: "Ada", active: true }
{"active":true,"name":"Ada"}

Multi-line input

For scripts that span multiple lines, start a block with %, type the lines, then close with % to submit:

> %
let users = [
    { name: "Ada", active: true },
    { name: "Grace", active: false }
]

return for user in users
    filter user.active
    return user.name
%
["Ada"]

Pass parameters

Use the --param flag to pass values into REPL queries. Parameters are accessible as @name:

$ferret repl --param greeting=hello

> return @greeting
"hello"

The --param flag follows the same format as the run command.

Runtime and browser flags

The REPL accepts the same runtime and browser flags as ferret run. For example, to start a REPL with a headless browser available:

$ferret repl --browser-headless

Wire runtime

Run the shell against an application-configured host:

$ferret repl --runtime wire --runtime-endpoint tcp://127.0.0.1:54321

The banner identifies the endpoint and the exact version supplied by the host. For the development host:

Welcome to Ferret REPL (Wire runtime: tcp://127.0.0.1:54321; version: v2.0.0-alpha.57)

The shell reuses one runtime and connection across submissions. Syntax diagnostics go to stderr and allow corrected queries. Transport loss or resource failure ends the shell; it never reconnects or falls back. The host owns browser integrations and filesystem policy, so explicit local browser or policy settings are rejected. See the Wire runtime guide for setup, compatibility, and metadata behavior.

Exit

Type exit or press Ctrl-D to leave the REPL. Ctrl+C stops the shell and interrupts pending input or execution.

Next steps