R""(

# Examples

* Start a shell providing `youtube-dl` from the `nixpkgs` flake:

  ```console
  # nix shell nixpkgs#youtube-dl
  # youtube-dl --version
  2020.11.01.1
  ```

* Start a shell providing GNU Hello from NixOS 20.03:

  ```console
  # nix shell nixpkgs/nixos-20.03#hello
  ```

* Run GNU Hello:

  ```console
  # nix shell nixpkgs#hello --command hello --greeting 'Hi everybody!'
  Hi everybody!
  ```

* Run multiple commands in a shell environment:

  ```console
  # nix shell nixpkgs#gnumake --command sh -c "cd src && make"
  ```

* Run GNU Hello in a chroot store:

  ```console
  # nix shell --store ~/my-nix nixpkgs#hello --command hello
  ```

* Start a shell providing GNU Hello in a chroot store:

  ```console
  # 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 `$PATH` variable
provides the specified [*installables*](./nix.md#installables). If no command is specified, it starts the
default shell of your user account specified by `$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:

```bash
#! /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:

```python
#! /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])