How to make a nix file which returns a derivation into an executable file?

luochen1990 · February 22, 2022, 1:13pm

Hi, guys, I’d like to make my nix script file into executable file via some shebang.

My first solution is use the nix-shell shebang like following:

(the file is named test.nix and chmod +x test.nix is executed)

#!/usr/bin/env nix-shell
#! nix-shell test.nix

{ pkgs ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/c9a97ff47bb0db44f4a504015a5d1cedb3094c85.tar.gz") {} }:

(pkgs.buildFHSUserEnv {
  name = "bash";
  targetPkgs = pkgs: (with pkgs; [
    python37
    python37Packages.pip
    python37Packages.virtualenv
    stdenv.cc.cc.lib
    pythonManylinuxPackages.manylinux2014Package
  ]);

  profile = ''
    run-some-test --with-some-args
  '';
}).env

But I cannot pass extra command line argument to bash this way.

So I think I can pass CLI arguments like:

$(nix-build --pure xxx.nix)/bin/bash --some-args

But I want to make it simple for users who need to run this test file and might not familier with nix. So the best way is to write the above line into the shebang of the nix file, is it possible?

luochen1990 · February 23, 2022, 6:49am

gist.github.com

https://gist.github.com/luochen1990/3f37aaa0a6a2578918c10b18e6ecdeca

nix-wrap

#!/usr/bin/env bash

#echo '$@ = ' "$@"

nixfile="$1"; shift
#echo "nixfile =" "$nixfile"

outpath="$(nix-build --pure $nixfile)"
#echo "outpath =" "$outpath"

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venv.nix

#!/usr/bin/env nix-wrap

# Usages:
#$ nix run -f ./venv.nix '' -- -c 'python --version'
#$ nix run -f ./venv.nix ''
#$ nix bundle -f ./venv.nix

let
  makeOverridable = f: f {} // { override = y: makeOverridable (x: f (x // y)); };
in

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Usage:

$ ./venv.nix bash -c "echo hi"

sternenseemann · February 25, 2022, 11:52am

You can also achieve this without a wrapper, but I wouldn’t recommend it, as it’s not officially supported and probably won’t remain stable.

There was some exploration in this direction (including some positively disgusting shebangs) in this thread: