Discovering just

What is just

I recently stumbled upon this article about creating internal or personal cli’s, using just-cli. After give it a try, it seems to be a great tool if you want to create some kind of personal cli or keep a set of commands in one place. As a test run at work, I replaced a set of (small) batch files (most of them oneliners and twoliners) with a single justfile.

My favorite practical features…

… compared to a simple set of multiple batch files:

• Commands can be documented, i prefer the syntax with an explicite doc attribute:

    [doc("some description of a command")]  

• Building on the previous point, just --list prints a nicely formatted list of all commands defined in the justfile (along with their description).

• Using [private] as attribute on a just command, you can take the command out of the help/usage list. This is e.g. typically used on the default command, like this:

    [private]
    default:
        just --list

• Different shells are supported and can be switched via a simple command, generally like this:

	set shell := ["SHELLCOMMAND", "ARG1"]

or

	set windows-shell := ["SHELLCOMMAND", "ARG1"]

• Arguments are by default defined by name (improving their documentational value), and are accessed via double braces, like this:

hello title name:
    echo Hello, {{title}} {{name}}

• Support for variables, e.g. you can define a long path to a file once and use the short variable name over and over again.

Code snippets for reference

A basic empty justfile

# use cmd.exe instead of sh:
set windows-shell := ["cmd.exe", "/c"]

# use powershell.exe instead of sh:
# set windows-shell := ["powershell.exe", "-NoLogo", "-Command"]

[private]
@default:
    just --list


[doc("print hello world-like")]
[positional-arguments]
[no-cd]
hello *args='':
    echo Hello, {{args}}

Defining and using variables

Variables are set using the assignment operator :=, variables, as well as command arguments, are accessed via double braces {{VAR}}.

myprog := 'D:\SYS\Programs\my_cool_app\myapp.exe'

@mp *args='':
	{{myprog}} {{args}}

For reference

Links

• just homepage
• just manual
• just github page
• Article which led me to it