beamr-cli

Command-line runner for beamr — load and execute .beam bytecode files compiled from Gleam (or Erlang) source.

Installation

cargo install beamr-cli

Or build from source:

cargo build --release -p beamr-cli

The binary is named beamr.

Usage

# Run a module's main/0 function
beamr my_module.beam

# Run a specific function with arguments
beamr proof.beam proof:factorial/1 -- 12
# => 479001600

# Alternative --entry flag syntax
beamr proof.beam --entry proof:fibonacci/1 -- 30
# => 832040

# Load dependency modules from a directory before running
beamr my_app.beam --dir ./build/dev/erlang/my_app/ebin

# Multiple dependency directories
beamr my_app.beam --dir ./deps/gleam_stdlib/ebin --dir ./deps/gleam_otp/ebin

# Check what imports a module needs before running
beamr imports my_module.beam

Entry point format

Entry points follow the Erlang convention: module:function/arity.

beamr hello.beam hello:greet/1 -- world

Arguments after -- are passed to the function. Integer literals are parsed as BEAM integers; everything else becomes a binary (string).

Import checking

beamr imports lists any unresolved imports a module needs. If the output is empty, beamr can run the module natively.

$ beamr imports my_module.beam
some_module:some_function/2

Use --dir to load the modules that provide those imports.

Typical Gleam workflow

# Write Gleam code
cat > hello.gleam << 'GLEAM'
pub fn main() {
  42
}
GLEAM

# Compile with Gleam
gleam build

# Run with beamr
beamr build/dev/erlang/hello/ebin/hello.beam
# => 42

License

Apache-2.0