Common evaluation options

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--arg name expr

Pass the value expr as the argument name to Nix functions.

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--arg-from-file name path

Pass the contents of file path as the argument name to Nix functions.

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--arg-from-stdin name

Pass the contents of stdin as the argument name to Nix functions.

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--argstr name string

Pass the string string as the argument name to Nix functions.

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--debugger

Start an interactive environment if evaluation fails.

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--eval-store store-url

The URL of the Nix store to use for evaluation, i.e. to store derivations (.drv files) and inputs referenced by them.

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--impure

Allow access to mutable paths and repositories.

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--include / -I path

Add 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 the NIX_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:// or https://, 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 the nixpkgs repository.

The URLs of the tarballs from the official nixos.org channels (see the manual page for nix-channel) can be abbreviated as channel:<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 the nixpkgs entry in the flake registry. Similarly,

-I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05

makes <nixpkgs> refer to a particular branch of the NixOS/nixpkgs repository on GitHub.

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--override-flake original-ref resolved-ref

Override the flake registries, redirecting original-ref to resolved-ref.

Logging-related options

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--debug

Set the logging verbosity level to ‘debug’.

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--log-format format

Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

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--print-build-logs / -L

Print full build logs on standard error.

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--quiet

Decrease the logging verbosity level.

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--verbose / -v

Increase the logging verbosity level.

Miscellaneous global options

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--help

Show usage information.

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--offline

Disable substituters and consider all previously downloaded files up-to-date.

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--option name value

Set the Nix configuration setting name to value (overriding nix.conf).

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--refresh

Consider all previously downloaded files out-of-date.

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--repair

During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.

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--version

Show version information.