cached-nix-shell is a caching layer for
nix-shell featuring instant startup time on subsequent runs.
It supports NixOS and Linux.
Install the release version from Nixpkgs:
nix-env -iA nixpkgs.cached-nix-shell
Or, install the latest development version from GitHub:
nix-env -if https://github.com/xzfc/cached-nix-shell/tarball/master
cached-nix-shell in the shebang line:
#! /usr/bin/env cached-nix-shell #! nix-shell -i python3 -p python print("Hello, World!")
$ cached-nix-shell ./hello.py $ cached-nix-shell -p python3 --run 'python --version'
Or use the
--wrap option for programs that call
$ cached-nix-shell --wrap stack build
$ time ./hello.py # first run; no cache used cached-nix-shell: updating cache Hello, World! ./hello.py 0.33s user 0.06s system 91% cpu 0.435 total $ time ./hello.py Hello, World! ./hello.py 0.02s user 0.01s system 97% cpu 0.029 total
Caching and cache invalidation
cached-nix-shell stores environment variables set up by
nix-shell and reuses them on subsequent runs.
It traces which files are read by
nix during an evaluation, and performs a proper cache invalidation if any of the used files are changed.
The cache is stored in
The following situations are covered:
import ./file.nixis used
- updating nix channels
The following situations aren't handled by
cached-nix-shell and may lead to staled cache:
builtins.fetchurlor other network builtins are used (e.g. in nixpkgs-mozilla)
There are related projects focused on using
nix-shellfor project developing: