mruby-bin-mirb

mirb (mruby interactive) is an interactive Ruby shell for mruby.

Usage

mirb [options]

Options

-v - print version and exit
-d - set $DEBUG to true
-r library - load the library before executing
--verbose - verbose mode

Tab Completion

mirb supports context-aware tab completion when built with a readline library.

Supported Completions

Methods on objects: Type an expression followed by . and press Tab
```
> "hello".up<Tab>
upcase  upcase!  upto
```
Local variables: Variables defined in the session
```
> my_var = 123
> my<Tab>
my_var
```
Global variables: Press Tab after $
```
> $std<Tab>
$stdout  $stderr  $stdin
```
Constants and classes: Capital letter followed by Tab
```
> Str<Tab>
String  Struct
```
Ruby keywords: At the start of expressions
```
> cla<Tab>
class
```

Readline Library Support

Tab completion works with:

GNU readline (default on Linux)
libedit (default on macOS/BSD)
linenoise (lightweight alternative)

Configuration

The readline library can be configured via the MRUBY_MIRB_READLINE environment variable:

bash

# Auto-detect (default)
rake

# Force specific library
MRUBY_MIRB_READLINE=readline rake    # GNU readline
MRUBY_MIRB_READLINE=libedit rake     # libedit
MRUBY_MIRB_READLINE=linenoise rake   # linenoise

# Disable readline (plain input mode)
MRUBY_MIRB_READLINE=none rake

Notes

Completion evaluates receiver expressions to determine available methods
Only simple receivers (variable names, constants) are evaluated for safety
Complex expressions like obj.method(). are not completed to avoid side effects
File path completion in require/load statements is planned for future versions

License

MIT License - see the mruby LICENSE file.