Run Bnlang Scripts from Command Line

The bnl CLI is the single entry point to the runtime. It can run a script file, evaluate inline code with -e, or drop into a REPL when called with no arguments.

Running a Script File

# Run a script
bnl hello.bnl

// file: hello.bnl
print("Hello, World!");

Inline Code with -e

bnl -e 'print(1 + 2);'
# 3

Starting the REPL

Running bnl with no arguments opens an interactive prompt. Useful for poking at the language or trying out stdlib calls.

bnl
> print("hi");
hi
> 1 + 2
3

Passing Arguments

Anything after the script path (or after the -e code) is forwarded to the script. Read them with sys.arg(i) / sys.argc().

// file: greet.bnl
import "sys" as sys;

var name = "Guest";
if (sys.argc() > 0) {
    name = sys.arg(0);
}
print("Hello,", name);

bnl greet.bnl Alice
# Output: Hello, Alice

Best Practices

  • Keep scripts small and focused — one entry point per file.
  • For anything past a handful of arguments, switch from sys.arg to the cli module for proper flag parsing.
  • Use bnl --version in CI logs so you know which interpreter built which output.