Command-line tools

Zap is a good fit for command-line tools that should start quickly, ship as a native binary, and keep their control flow easy to inspect.

Start a project

Create and run a Thor project:

thor new greet
cd greet
thor run

Thor builds the executable into build/. Add project-level compiler options, native libraries, and import mappings in thor.toml instead of maintaining a long shell command.

Read arguments

std/process exposes the argument count and individual arguments:

import "std/process";

fun main() Int {
    if process.argc() != 2 {
        eprintln("usage: greet <name>");
        return 1;
    }

    println("Hello, " + process.argv(1) + "!");
    return 0;
}

main returns the program’s exit status. Return 0 for success and a nonzero value when the command cannot complete.

Keep failure paths local

File operations are failable. Handle an expected failure where the command can give the user useful context:

import "std/fs";

fun main() Int {
    var text: String = fs.readFile("message.txt") or err {
        eprintln("could not read message.txt");
        return 1;
    };

    println(text);
    return 0;
}

Read Error handling for ?, or, and or err. For filesystem APIs, see std/fs.