nix-build

# Name

`nix-build` - build a Nix expression

# Synopsis

`nix-build` [paths…] [`--arg` name value] [`--argstr` name value] [{`--attr` | `-A`} attrPath] [`--no-out-link`] [`--dry-run`] [{`--out-link` | `-o`} outlink]

# Description

The `nix-build` command builds the derivations described by the Nix expressions in paths. If the build succeeds, it places a symlink to the result in the current directory. The symlink is called `result`. If there are multiple Nix expressions, or the Nix expressions evaluate to multiple derivations, multiple sequentially numbered symlinks are created (`result`, `result-2`, and so on).

If no paths are specified, then `nix-build` will use `default.nix` in the current directory, if it exists.

If an element of paths starts with `http://` or `https://`, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must include a single top-level directory containing at least a file named `default.nix`.

`nix-build` is essentially a wrapper around `nix-instantiate` (to translate a high-level Nix expression to a low-level store derivation) and `nix-store --realise` (to build the store derivation).

> Warning

> The result of the build is automatically registered as a root of the Nix garbage collector. This root disappears automatically when the `result` symlink is deleted or renamed. So don’t rename the symlink.

# Options

All options not listed here are passed to `nix-store --realise`, except for `--arg` and `--attr` / `-A` which are passed to `nix-instantiate`.

- `--no-out-link`
  Do not create a symlink to the output path. Note that as a result the output does not become a root of the garbage collector, and so might be deleted by `nix-store --gc`.

- `--dry-run`
  Show what store paths would be built or downloaded.

- `--out-link` / `-o` outlink
  Change the name of the symlink to the output path created from `result` to outlink.

The following common options are supported:

# Examples

    $ nix-build '<nixpkgs>' -A firefox
    store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
    /nix/store/d18hyl92g30l...-firefox-1.5.0.7

    $ ls -l result
    lrwxrwxrwx  ...  result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7

    $ ls ./result/bin/
    firefox  firefox-config

If a derivation has multiple outputs, `nix-build` will build the default (first) output. You can also build all outputs:

    $ nix-build '<nixpkgs>' -A openssl.all

This will create a symlink for each output named `result-outputname`. The suffix is omitted if the output name is `out`. So if `openssl` has outputs `out`, `bin` and `man`, `nix-build` will create symlinks `result`, `result-bin` and `result-man`. It’s also possible to build a specific output:

    $ nix-build '<nixpkgs>' -A openssl.man

This will create a symlink `result-man`.

Build a Nix expression given on the command line:

    $ nix-build -E 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
    $ cat ./result
    bar

Build the GNU Hello package from the latest revision of the master branch of Nixpkgs:

    $ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello