REPL mode

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Run your command tree as an interactive shell. Same parsing, same validation, same handlers.

Start it

Cheer.Repl.start(MyApp.CLI.Root, prog: "my-app")
my-app> greet world --loud
HELLO, WORLD!
my-app> db migrate --target 20240101
Connecting to database...
Migrating to version 20240101...
my-app> help
...
my-app> exit

Built-in commands

  • help / ? -- print help for the root command (or a sub, with help <sub>).
  • exit / quit / Ctrl+D -- leave the REPL.

Tokenization

The REPL tokenizes each input line like a shell: whitespace-separated, single and double quotes supported, backslash escapes inside strings.

my-app> greet "Ada Lovelace" --loud
my-app> run 'some command with spaces'

Exit codes

REPL mode doesn't exit the host process on errors -- a failed command prints its error and returns control to the prompt. That makes it safe to embed inside longer-running tools.

When to use it

  • Interactive admin tools for long-lived services.
  • Demo and teaching contexts where typing one command at a time beats typing a full invocation each turn.
  • Workflows where you want the parser's validation without wrapping every call in a subshell.

See also