nix-shell

nix shell

The canonical form for running a single command in a temporary nix environment:

nix shell nixpkgs#<package> -c <command> [args...]

The -c flag tells nix shell to exec the following arguments as a command. Everything after -c is passed straight to the shell, so quoting works naturally.

DO NOT, under any circumstances, double-quote "<command> [args...]" together. This will cause bash to treat the entire thing as the executable name:

• Wrong: nix shell nixpkgs#python3 -c "python3 foo.py arg1 arg2"
• RIGHT: nix shell nixpkgs#python3 -c python3 foo.py arg1 arg2

Single-package one-off

nix shell nixpkgs#jq -c jq '.foo' file.json
nix shell nixpkgs#yq -c yq eval '.foo.bar' file.yml
nix shell nixpkgs#httpie -c https httpbin.org/json

Multiple packages in one shell

For ephemeral environments with multiple tools (where the "command" is sh):

nix shell nixpkgs#jq nixpkgs#yq nixpkgs#curl -c sh

This drops you into an interactive shell with all three available. Exit with exit or ^D.

When to use nix run instead

nix run is more concise when you just need to run a tool's default binary and don't need to control the invoked command name:

nix run nixpkgs#jq -- -r '.name' file.json

Use nix run when:

• You want a single command with arguments (everything after -- is passed to the binary)
• The package's default binary name matches what you need
• You don't need multiple packages simultaneously

Use nix shell when:

• You need to chain multiple commands in the same ephemeral environment
• The command name differs from the package name (e.g., nixpkgs#nodePackages.prettier)
• You want an interactive shell with multiple tools available

Python with packages (playwright, requests, etc.)

nix shell nixpkgs#python3Packages.<name> doesn't work — the Python binary won't see the package. Instead, use nix eval --apply to get the python3.withPackages derivation path, then ask nix shell for its out output:

nix shell "$(
  nix eval nixpkgs#python3 --raw --apply \
    'py: (py.withPackages (p: [ p.requests ])).drvPath'
)^out" -c python3 -c '
import requests
print(requests.get("https://httpbin.org/json").json()["slideshow"]["title"])
'

For multiple packages/tools, add them to the same shell:

nix shell "$(
  nix eval nixpkgs#python3 --raw --apply \
    'py: (py.withPackages (p: [ p.playwright ])).drvPath'
)^out" \
  nixpkgs#chromium \
  -c python3 -c '
from playwright.sync_api import sync_playwright
print("works")
'

Important details:

• Use .drvPath with ^out; plain .outPath may be unrealized.
• Keep ^out outside the command substitution, as part of the installable path.
• If invoking the store path directly instead of via nix shell, use nix build --no-link --print-out-paths to realize the output first.

Finding available packages

nix search nixpkgs <query>

Replacing missing commands

If a command fails with "command not found", wrap it with nix shell instead of installing the package globally:

# instead of: apt install jq  (never)
# instead of: nix profile install nixpkgs#jq  (avoid for one-offs)
nix shell nixpkgs#jq -c jq '.foo' data.json