nur - simple taskrunner


nur - the simple nu based task runner

nur is a simple, yet very powerful task runner. It borrows ideas from b5 and just, but uses nu scripting to define the tasks. This allows for very powerful, yet well-structured tasks.

Warning / disclaimer

In its current state nur is more or less a beta software. I wanted to put it out there, so I may receive some feedback. But I am only just starting using this in some production setup myself. So feel free to poke around with this, but be aware this is far from being finished or anything. Meaning: There might be dragons!

Usage example

nur allows you to execute tasks define in a file called nurfile. It will look through your current working directory and all its parents to look for this file. When it has found the nurfile it will change to the directory the file was found in and then source the file into nu script. You can define tasks like this:

# Just tell anybody or the "world" hello
def "nur hello" [
    name: string = "world"  # The name to say hello to
] {
    print $"hello ($name)"

The important bit is that you define your tasks as subcommands for "nur". If you then execute nur hello it will print "hello world", meaning it did execute the task hello in your nurfile. You can also use nur --help to get some details on how to use nur and nur --help hello to see what this hello task accepts as parameters.

You may also pass arguments to your nur tasks, like using nur hello bob to pass "bob" as the name to the "hello" task. This supports all parameter variants normal nu scripts could also handle. You may use nur --help <task-name> to see the help for an available command.

Your tasks then can do whatever you want them to do in nu script. This allows for very structured usage of for example docker to run/manage your project needs. But it can also execute simple commands like you would normally do in your shell (like npm ci or something). nur is not tight to any programming language, packaging system or anything. As in the end the nurfile is basically a normal nu script you can put into this whatever you like.

See nu custom commands for details on how to define tasks and at least read through the nu quick tour to understand some basics and benefits about nu scripting.

Installing nur

As of now nur is not available in common package managers. This is however no issue as cargo allows you to install packages into your own user directory.

Note: You need to have cargo installed for this to work. See cargo install docs for details on getting cargo running.

Just run cargo install nur to install nur for your current user. The nur binary will be added in $HOME/.cargo/bin (or $"($env.HOME)/.cargo/bin" in nu shell). Make sure to add this to $PATH (or $env.PATH in nu shell).

Shell example (like Bash, zsh, ...):

cargo install nur
export PATH="$HOME/.cargo/bin:$PATH"  # put this into your .bashrc, .zshrc or similar
nur --version

nu shell example:

cargo install nur
$env.PATH = ($env.PATH | split row (char esep) | prepend [$'($nu.home-path)/bin'])  # put this into $nu.env-path
nur --version

Working with nur

As shown above you can use subcommands to "nur" to add your tasks. This section will give you some more details and some hints how to do this in the best way possible.

About the nurfile

Your tasks are defined in a file called nurfile. This file is a normal nu script and may use nu commands to define nur tasks. All tasks must be defined as subcommands to "nur", you still will be able to define any other commands and use those as helpers in your tasks. Only subcommands to "nur" will be exposed by running nur.

In addition you may add a file called nurfile.local to define personal, additional tasks. I recommend adding the nurfile to git, while nurfile.local should be ignored. This allows each developer to have their own additional set of tasks.

Some basics that nur provides

  • nur tasks will always be run inside the directory the file nurfile was found in. If you place a nurfile in your project root (git root) you will be able to call tasks from anywhere inside the project.
  • nur will provide the internal state and config in the variable $nur, containing:
    • $ The path nur was executed in
    • $nur.project-path: The path nur executes the tasks in, this means the path the nurfile was found
    • $nur.task-name: The name of the task being executed, if any

Adding some arguments to your tasks

I highly recommend reading nu custom commands for details, but I will try to show you the most important bits right here. I will use the term "nur tasks" to talk about "nu (sub)commands" in the following section.

nur tasks can receive three different kinds of arguments:

  • Named, positional arguments: def "nur taskname" [argument1, argument2] { ... }
    • Adding a ? after the parameter name makes it optional
    • Above example provides the variables $argument1 and $argument2 in the task
  • Flags as parameters: def "nur taskname" [--argument1: string, --argument-number2: int] { ... }
    • If you want to have named flags that can actually receive any values, you need to add a type (see below for typing)
    • Flags are always optional, default value will be null unless defined otherwise (see below for default values)
    • Flags will provide variables names without the leading --
    • Flags will be available in your task code as variables with all - replaced by _
    • Above example provides the variables $argument1 and $argument_number2 in the task
  • Boolean flags: def "nur taskname" [--switch] { ... }
    • Boolean flags must NOT be typed
    • Those can only receive the values true/false, with false being the default
    • Above example provides the variable $switch in the task
  • Rest parameters might consume the rest of the arguments: def "nur taskname" [] { ... }
    • Above example provides the variable $rest in the task

Arguments can (and should) be typed, you can use argument_name: type for doing so. A typed argument could look like this:
def "nur taskname" [argument1: string, argument2: int] { ... }
(see parameter types for a full list of available types)

Also arguments can have a default value, you can use argument_name = "value" to set the default value. An example using a default value could look like this:
def "nur taskname" [argument1 = "value", argument2 = 10] { ... }

Adding docs to your command

You may add docs by adding commands to your nur tasks. See the usage example above and the nu command documentation section.

Basic rule is that the commend right above your task will be used as a description for that task. Comments next to any argument will be used to document that argument.

Calling system commands from nur

If you want to run external commands you might run into the issue that nu itself provides some builtin commands that might match the name of the command you want to run. This for example is the case for sort, where nu has it's own version (see sort command). Most of the time it makes sense to use the versions nu provides as those implement all the pipeline improvements of nu. If you want to call the external command and not the builton function by nu use ^sort instead of sort in your nur tasks.

The same rule applies to your user defined functions, you would for example provide a function named grep (def grep [] { ... }) which could call the grep command using ^grep.

Provide nur tasks for running normal shell commands

If you want to use a nur to run any normal command - for example to ensure you can run this in any subdirectory of your project - I recommend using the following schema (using the poetry package manager as an example):

def --wrapped "nur poetry" [...args] {
    poetry ...$args

The important bit is using --wrapped, so the nu parser will not try to match flags starting with - into your nur task.

See the docs for def for some more details.

Some notes about pipelines and how nu handles those

Normal UNIX shells always use text to pass data from stdout (or stderr) to the next command via stdin. This is pretty easy to implement and a very slim contract to follow. nu however works quite different from this. Instead of passing test when using pipelines it tried to use structured data - think of this like passing JSON between the different command. This increases the flexibility and structured way to work with the data in a great way.

For example getting the ID of a running container in docker would look somewhat like this in a normal UNIX shell:
docker ps | grep some-name | grep -n 1 | awk '{print $1}'

This works for most of the cases, but might produce errors for example of a container named this-also-contains-some-name-in-its-name exists. This issue exists as we are parsing text data, not some actual structured data. So having the name anywhere in a line will result in that line being used. (Note: I know about docker ps --filter ..., this is just to explain the overall issue of parsing text data)

nu works on structured data and provides commands to filter, sort or restructure that data in any way you like. Also nu provides mechanics to import text data into this structured format. Getting the docker ps text data input nu can for example be done using docker ps | from ssv ("ssv" stands for "space-separated values"), see the command from for more possible input formats.

To get the first container matching using the image some-name you could use this command:
docker ps | from ssv | where IMAGE == "some-name" | get "CONTAINER ID" | first

This is using the where command to match only a single row and then the get command to reduce the row to just one column. There are also many more commands to work with structured data.

This way of working with command data in a very structured form is very much superior to how normal shells used to work. This is especially good when you are creating more complex scripts and thus also true for the tasks you will write in your task runner. This is why I did choose nu for creating nur.

I recommend reading thinking in nu to get a grasp about this concept and start using nu script in nur in a very structured way.

Why nur + some history

For me nur is the next logical step after I created b5. b5 is based on running bash code and allowing users to do this in a somewhat ordered matter. Initially b5 even was just some bash script, but then eventually I figured bash is just not enough to handle my requirements. So I switched to using Python, but b5 was still based on bash, as it would generate bash code and then just execute the code. One issue I always had with this approach was that again bash isn't that nice to write complex things without introducing issues everywhere. Look for example at parameter handling.

Then along came just, which did implement its own language you could use to write your justfile. This language was inspired by what a Makefile would look like, still without the issues Makefile's impose when using those as your task runner. Also, it did include a very nice way to define task arguments, parse those, care about validation etc. Still the way just works is either to execute the task line by line (and not having any context between those commands) or define some script language to execute the full command (meaning using something like bash again). So just - at least for me - is a great step forward, but still not what I had in mind when creating b5 and what I would like to do with a task runner.

Then I came across nu, especially the nu shell. This did become my default shell after a while, and I am using it as of now. nu feels nicely designed, has a very structured way to execute commands and also handle their "response" data (stdout/err) - as everything is structured data there. This is way better than the original UNIX approach of always passing text data. Also nu allows you to have simple functions, that - as with just - handle argument parsing for you. So this did look like the perfect combination for something like a task runner.

Of course, you could just define some nu functions to completely create a task runner and that would already be better than b5 or just. But this would also mean that every dev using this task runner would need to switch to nu first. So I decided to try the hard route and create my own rust based cli tool that would parse a nu script and then execute tasks defined in this script.

This is what you are seeing here. nur will load the nurfile defined in your project directory and then allows you to execute tasks from this file. As it is its own binary you can easily use nur from bash, zsh and possibly even PowerShell - whatever you prefer. Still you will be able to have the nu superpowers inside your defined tasks.

About the name

nur stands for "nu run". Basically it should be "nu run task", which would lead to "nurt" - but then I decided for just "nur" as:

  • nur is very fast to type (one less character πŸ’ͺ)
  • nur is the reverse of run, which I like as a side effect πŸ₯³
  • and then as a nice and also weird side effect: You could translate "just" to "nur" in german πŸ˜‚


If you want to contribute to this project, feel free to just fork the project, create a dev branch in your fork and then create a pull request (PR). If you are unsure about whether your changes really suit the project please create an issue first, to talk about this.

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