Nix 2.29.1
Nix, the purely functional package manager; unstable internal interfaces
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R""(
Start a shell providing youtube-dl from the nixpkgs flake:
Start a shell providing GNU Hello from NixOS 20.03:
Run GNU Hello:
Run multiple commands in a shell environment:
Run GNU Hello in a chroot store:
Start a shell providing GNU Hello in a chroot store:
Note that it's necessary to specify bash explicitly because your default shell (e.g. /bin/bash) generally will not exist in the chroot.
nix shell runs a command in an environment in which the $PATH variable provides the specified installables. If no command is specified, it starts the default shell of your user account specified by $SHELL.
You can use nix as a script interpreter to allow scripts written in arbitrary languages to obtain their own dependencies via Nix. This is done by starting the script with the following lines:
where real-interpreter is the “real” script interpreter that will be invoked by nix shell after it has obtained the dependencies and initialised the environment, and installables are the attribute names of the dependencies in Nixpkgs.
The lines starting with #! nix specify options (see above). Note that you cannot write #! /usr/bin/env nix shell -i ... because many operating systems only allow one argument in #! lines.
For example, here is a Python script that depends on Python and the prettytable package:
Similarly, the following is a Perl script that specifies that it requires Perl and the HTML::TokeParser::Simple and LWP packages:
Sometimes you need to pass a simple Nix expression to customize a package like Terraform:
Note
You must use double backticks ( `` ) when passing a simple Nix expression in a nix shell shebang.
Finally, using the merging of multiple nix shell shebangs the following Haskell script uses a specific branch of Nixpkgs/NixOS (the 21.11 stable branch):
If you want to be even more precise, you can specify a specific revision of Nixpkgs:
#!nix shell --override-input nixpkgs github:NixOS/nixpkgs/eabc38219184cc3e04a974fe31857d8e0eac098d
You can also use a Nix expression to build your own dependencies. For example, the Python example could have been written as:
where the file deps.nix in the same directory as the #!-script contains:
)""