nix tip: shell shabang

A feature I discovered recently is that nix-shell can be used as an interpreter

#!/usr/bin/env nix-shell
#!nix-shell -i bash -p bash htop

echo hello world
which htop

It even works for python

#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p python3Packages.pillow python3Packages.ansicolor

# scale image by 50%
import sys, PIL.Image, ansicolor
path = sys.argv[1]
image = PIL.Image.open(path)
factor = 0.5
image = image.resize((round(image.width * factor), round(image.height * factor)))
path = path + ".s50.jpg"
image.save(path)
print(ansicolor.green(f"done {path}"))

Discovered on the wiki page at https://nixos.wiki/wiki/Nix-shell_shebang

• nix