Manpages - nix3-fmt.1

Warning
This program is experimental and its interface is subject to change.

#+end_quote

Name

nix fmt - reformat your code in the standard style

nix fmt [/option/…] args…

With nixpkgs-fmt:

# flake.nix
{
  outputs = { nixpkgs, self }: {
    formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixpkgs-fmt;
  };
}

With nixfmt:

# flake.nix
{
  outputs = { nixpkgs, self }: {
    formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixfmt;
  };
}

With Alejandra:

# flake.nix
{
  outputs = { nixpkgs, self }: {
    formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.alejandra;
  };
}

nix fmt will rewrite all Nix files (*.nix) to a canonical format using the formatter specified in your flake.

--arg name expr Pass the value expr as the argument name to Nix functions.
--arg-from-file name path Pass the contents of file path as the argument name to Nix functions.
--arg-from-stdin name Pass the contents of stdin as the argument name to Nix functions.
--argstr name string Pass the string string as the argument name to Nix functions.
--debugger Start an interactive environment if evaluation fails.
--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.
--impure Allow access to mutable paths and repositories.
--include / -I path Add path to search path entries used to resolve lookup paths This option may be given multiple times. Paths added through -I take precedence over the nix-path configuration setting and the NIX_PATH environment variable.
--override-flake original-ref resolved-ref Override the flake registries, redirecting original-ref to resolved-ref.

--commit-lock-file Commit changes to the flake's lock file.
--inputs-from flake-url Use the inputs of the specified flake as registry entries.
--no-registries

Don't allow lookups in the flake registries.

DEPRECATED

Use --no-use-registries instead.
--no-update-lock-file Do not allow any updates to the flake's lock file.
--no-write-lock-file Do not write the flake's newly generated lock file.
--output-lock-file flake-lock-path Write the given lock file instead of flake.lock within the top-level flake.
--override-input input-path flake-url Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.
--recreate-lock-file

Recreate the flake's lock file from scratch.

DEPRECATED

Use nix flake update instead.
--reference-lock-file flake-lock-path Read the given lock file instead of flake.lock within the top-level flake.
--update-input input-path

Update a specific flake input (ignoring its previous entry in the lock file).

DEPRECATED

Use nix flake update instead.

--debug Set the logging verbosity level to ‘debug'.
--log-format format Set the format of log output; one of raw, internal-json, bar or bar-with-logs.
--print-build-logs / -L Print full build logs on standard error.
--quiet Decrease the logging verbosity level.
--verbose / -v Increase the logging verbosity level.

--help Show usage information.
--offline Disable substituters and consider all previously downloaded files up-to-date.
--option name value Set the Nix configuration setting name to value (overriding nix.conf).
--refresh Consider all previously downloaded files out-of-date.
--repair During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.
--version Show version information.

--expr expr Interpret installables as attribute paths relative to the Nix expression expr.
--file / -f file Interpret 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.