Warning
This program is experimental and its interface is subject to change.
Name
nix shell
- run a shell in which the specified packages are available
Synopsis
nix shell
[option...] installables...
Examples
-
Start a shell providing
youtube-dl
from thenixpkgs
flake:# nix shell nixpkgs#youtube-dl # youtube-dl --version 2020.11.01.1
-
Start a shell providing GNU Hello from NixOS 20.03:
# nix shell nixpkgs/nixos-20.03#hello
-
Run GNU Hello:
# nix shell nixpkgs#hello --command hello --greeting 'Hi everybody!' Hi everybody!
-
Run multiple commands in a shell environment:
# nix shell nixpkgs#gnumake --command sh -c "cd src && make"
-
Run GNU Hello in a chroot store:
# nix shell --store ~/my-nix nixpkgs#hello --command hello
-
Start a shell providing GNU Hello in a chroot store:
# nix shell --store ~/my-nix nixpkgs#hello nixpkgs#bashInteractive --command bash
Note that it's necessary to specify
bash
explicitly because your default shell (e.g./bin/bash
) generally will not exist in the chroot.
Description
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
.
Use as a #!
-interpreter
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:
#! /usr/bin/env nix
#! nix shell installables --command real-interpreter
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:
#! /usr/bin/env nix
#! nix shell github:tomberek/-#python3With.prettytable --command python
import prettytable
# Print a simple table.
t = prettytable.PrettyTable(["N", "N^2"])
for n in range(1, 10): t.add_row([n, n * n])
print t
Similarly, the following is a Perl script that specifies that it
requires Perl and the HTML::TokeParser::Simple
and LWP
packages:
#! /usr/bin/env nix
#! nix shell github:tomberek/-#perlWith.HTMLTokeParserSimple.LWP --command perl -x
use HTML::TokeParser::Simple;
# Fetch nixos.org and print all hrefs.
my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
while (my $token = $p->get_tag("a")) {
my $href = $token->get_attr("href");
print "$href\n" if $href;
}
Sometimes you need to pass a simple Nix expression to customize a package like Terraform:
#! /usr/bin/env nix
#! nix shell --impure --expr ``
#! nix with (import (builtins.getFlake ''nixpkgs'') {});
#! nix terraform.withPlugins (plugins: [ plugins.openstack ])
#! nix ``
#! nix --command bash
terraform "$@"
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):
#!/usr/bin/env nix
#!nix shell --override-input nixpkgs github:NixOS/nixpkgs/nixos-21.11
#!nix github:tomberek/-#haskellWith.download-curl.tagsoup --command runghc
import Network.Curl.Download
import Text.HTML.TagSoup
import Data.Either
import Data.ByteString.Char8 (unpack)
-- Fetch nixos.org and print all hrefs.
main = do
resp <- openURI "https://nixos.org/"
let tags = filter (isTagOpenName "a") $ parseTags $ unpack $ fromRight undefined resp
let tags' = map (fromAttrib "href") tags
mapM_ putStrLn $ filter (/= "") tags'
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:
#! /usr/bin/env nix
#! nix shell --impure --file deps.nix -i python
where the file deps.nix
in the same directory as the #!
-script
contains:
with import <nixpkgs> {};
python3.withPackages (ps: with ps; [ prettytable ])
Options
-
--command
/-c
command argsCommand and arguments to be executed, defaulting to
$SHELL
-
--ignore-environment
/-i
Clear the entire environment (except those specified with
--keep
). -
--keep
/-k
nameKeep the environment variable name.
-
Read installables from the standard input. No default installable applied.
-
--unset
/-u
nameUnset the environment variable name.
Common evaluation options
-
--arg
name exprPass the value expr as the argument name to Nix functions.
-
--arg-from-file
name pathPass the contents of file path as the argument name to Nix functions.
-
--arg-from-stdin
namePass the contents of stdin as the argument name to Nix functions.
-
--argstr
name stringPass the string string as the argument name to Nix functions.
-
Start an interactive environment if evaluation fails.
-
--eval-store
store-urlThe URL of the Nix store to use for evaluation, i.e. to store derivations (
.drv
files) and inputs referenced by them. -
Allow access to mutable paths and repositories.
-
--include
/-I
pathAdd path to the Nix search path. The Nix search path is initialized from the colon-separated
NIX_PATH
environment variable, and is used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e.,<nixpkgs>
).For instance, passing
-I /home/eelco/Dev -I /etc/nixos
will cause Nix to look for paths relative to
/home/eelco/Dev
and/etc/nixos
, in that order. This is equivalent to setting theNIX_PATH
environment variable to/home/eelco/Dev:/etc/nixos
It is also possible to match paths against a prefix. For example, passing
-I nixpkgs=/home/eelco/Dev/nixpkgs-branch -I /etc/nixos
will cause Nix to search for
<nixpkgs/path>
in/home/eelco/Dev/nixpkgs-branch/path
and/etc/nixos/nixpkgs/path
.If a path in the Nix search path starts with
http://
orhttps://
, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must consist of a single top-level directory. For example, passing-I nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz
tells Nix to download and use the current contents of the
master
branch in thenixpkgs
repository.The URLs of the tarballs from the official
nixos.org
channels (see the manual page fornix-channel
) can be abbreviated aschannel:<channel-name>
. For instance, the following two flags are equivalent:-I nixpkgs=channel:nixos-21.05 -I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz
You can also fetch source trees using flake URLs and add them to the search path. For instance,
-I nixpkgs=flake:nixpkgs
specifies that the prefix
nixpkgs
shall refer to the source tree downloaded from thenixpkgs
entry in the flake registry. Similarly,-I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05
makes
<nixpkgs>
refer to a particular branch of theNixOS/nixpkgs
repository on GitHub. -
--override-flake
original-ref resolved-refOverride the flake registries, redirecting original-ref to resolved-ref.
Common flake-related options
-
Commit changes to the flake's lock file.
-
--inputs-from
flake-urlUse the inputs of the specified flake as registry entries.
-
Don't allow lookups in the flake registries.
DEPRECATED
Use
--no-use-registries
instead. -
Do not allow any updates to the flake's lock file.
-
Do not write the flake's newly generated lock file.
-
--output-lock-file
flake-lock-pathWrite the given lock file instead of
flake.lock
within the top-level flake. -
--override-input
input-path flake-urlOverride a specific flake input (e.g.
dwarffs/nixpkgs
). This implies--no-write-lock-file
. -
Recreate the flake's lock file from scratch.
DEPRECATED
Use
nix flake update
instead. -
--reference-lock-file
flake-lock-pathRead the given lock file instead of
flake.lock
within the top-level flake. -
--update-input
input-pathUpdate a specific flake input (ignoring its previous entry in the lock file).
DEPRECATED
Use
nix flake update
instead.
Logging-related options
-
Set the logging verbosity level to 'debug'.
-
--log-format
formatSet the format of log output; one of
raw
,internal-json
,bar
orbar-with-logs
. -
--print-build-logs
/-L
Print full build logs on standard error.
-
Decrease the logging verbosity level.
-
--verbose
/-v
Increase the logging verbosity level.
Miscellaneous global options
-
Show usage information.
-
Disable substituters and consider all previously downloaded files up-to-date.
-
--option
name valueSet the Nix configuration setting name to value (overriding
nix.conf
). -
Consider all previously downloaded files out-of-date.
-
During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.
-
Show version information.
Options that change the interpretation of installables
-
--expr
exprInterpret installables as attribute paths relative to the Nix expression expr.
-
--file
/-f
fileInterpret installables as attribute paths relative to the Nix expression stored in file. If file is the character -, then a Nix expression will be read from standard input. Implies
--impure
.
Note
See
man nix.conf
for overriding configuration settings with command line flags.