Adding `meta.outputsToInstall` to that derivation will make `nix-env` only install files from the specified outputs.

  ```nix
  # example-outputs.nix
  import ./example.nix // { meta.outputsToInstall = [ "bar" ]; }
  ```

  ```console
  $ nix-env --install --file example-outputs.nix
  installing 'example'
  $ ls ~/.nix-profile
  bar-file
  manifest.nix
  ```


# Options

- `--prebuilt-only` / `-b`

  Use only derivations for which a substitute is registered, i.e.,
  there is a pre-built binary available that can be downloaded in lieu
  of building the derivation. Thus, no packages will be built from
  source.

- `--preserve-installed` / `-P`

  Do not remove derivations with a name matching one of the
  derivations being installed. Usually, trying to have two versions of
  the same package installed in the same generation of a profile will
  lead to an error in building the generation, due to file name
  clashes between the two versions. However, this is not the case for
  all packages.

- `--remove-all` / `-r`

  Remove all previously installed packages first. This is equivalent
  to running `nix-env --uninstall '.*'` first, except that everything happens
  in a single transaction.

{{#include ./opt-common.md}}

{{#include ../opt-common.md}}

{{#include ./env-common.md}}

{{#include ../env-common.md}}

# Examples

To install a package using a specific attribute path from the active Nix expression:

```console
$ nix-env --install --attr gcc40mips
installing `gcc-4.0.2'
$ nix-env --install --attr xorg.xorgserver
installing `xorg-server-1.2.0'
```

To install a specific version of `gcc` using the derivation name:

```console
$ nix-env --install gcc-3.3.2
installing `gcc-3.3.2'
uninstalling `gcc-3.1'
```

Using attribute path for selecting a package is preferred,
as it is much faster and there will not be multiple matches.

Note the previously installed version is removed, since
`--preserve-installed` was not specified.

To install an arbitrary version:

```console
$ nix-env --install gcc
installing `gcc-3.3.2'
```

To install all derivations in the Nix expression `foo.nix`:

```console
$ nix-env --file ~/foo.nix --install '.*'
```

To copy the store path with symbolic name `gcc` from another profile:

```console
$ nix-env --install --from-profile /nix/var/nix/profiles/foo gcc
```

To install a specific [store derivation] (typically created by
`nix-instantiate`):

```console
$ nix-env --install /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv
```

To install a specific output path:

```console
$ nix-env --install /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3
```

To install from a Nix expression specified on the command-line:

```console
$ nix-env --file ./foo.nix --install --expr \
    'f: (f {system = "i686-linux";}).subversionWithJava'
```

I.e., this evaluates to `(f: (f {system =
"i686-linux";}).subversionWithJava) (import ./foo.nix)`, thus selecting
the `subversionWithJava` attribute from the set returned by calling the
function defined in `./foo.nix`.

A dry-run tells you which paths will be downloaded or built from source:

```console
$ nix-env --file '<nixpkgs>' --install --attr hello --dry-run
(dry run; not doing anything)
installing ‘hello-2.10’
this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
  /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
  ...
```

To install Firefox from the latest revision in the Nixpkgs/NixOS 14.12
channel:

```console
$ nix-env --file https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz --install --attr firefox
```