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

Name

nix fmt - reformat your code in the standard style

Synopsis

nix fmt [option...] args...

Examples

With nixpkgs-fmt:

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

• Format the current flake: $ nix fmt

• Format a specific folder or file: $ nix fmt ./folder ./file.nix

With nixfmt:

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

• Format specific files: $ nix fmt ./file1.nix ./file2.nix

With Alejandra:

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

• Format the current flake: $ nix fmt

• Format a specific folder or file: $ nix fmt ./folder ./file.nix

Description

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

Options

Common evaluation options:

• --arg name expr

  Pass the value expr 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 Nix store to use for evaluations.

• --impure

  Allow access to mutable paths and repositories.

• --include / -I path

  Add path to the list of locations used to look up <...> file names.

• --override-flake original-ref resolved-ref

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

Common flake-related options:

• --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. This option is deprecated; use --no-use-registries.

• --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.

• --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.

• --update-input input-path

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

Logging-related options:

• --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.

Miscellaneous global options:

• --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.

• --version

  Show version information.

Options that change the interpretation of installables:

• --derivation

  Operate on the store derivation rather than its outputs.

• --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.

Options to override configuration settings:

• --accept-flake-config

  Enable the accept-flake-config setting.

• --access-tokens value

  Set the access-tokens setting.

• --allow-dirty

  Enable the allow-dirty setting.

• --allow-import-from-derivation

  Enable the allow-import-from-derivation setting.

• --allow-new-privileges

  Enable the allow-new-privileges setting.

• --allow-symlinked-store

  Enable the allow-symlinked-store setting.

• --allow-unsafe-native-code-during-evaluation

  Enable the allow-unsafe-native-code-during-evaluation setting.

• --allowed-impure-host-deps value

  Set the allowed-impure-host-deps setting.

• --allowed-uris value

  Set the allowed-uris setting.

• --allowed-users value

  Set the allowed-users setting.

• --auto-allocate-uids

  Enable the auto-allocate-uids setting.

• --auto-optimise-store

  Enable the auto-optimise-store setting.

• --bash-prompt value

  Set the bash-prompt setting.

• --bash-prompt-prefix value

  Set the bash-prompt-prefix setting.

• --bash-prompt-suffix value

  Set the bash-prompt-suffix setting.

• --build-hook value

  Set the build-hook setting.

• --build-poll-interval value

  Set the build-poll-interval setting.

• --build-users-group value

  Set the build-users-group setting.

• --builders value

  Set the builders setting.

• --builders-use-substitutes

  Enable the builders-use-substitutes setting.

• --commit-lockfile-summary value

  Set the commit-lockfile-summary setting.

• --compress-build-log

  Enable the compress-build-log setting.

• --connect-timeout value

  Set the connect-timeout setting.

• --cores value

  Set the cores setting.

• --diff-hook value

  Set the diff-hook setting.

• --download-attempts value

  Set the download-attempts setting.

• --download-speed value

  Set the download-speed setting.

• --enforce-determinism

  Enable the enforce-determinism setting.

• --eval-cache

  Enable the eval-cache setting.

• --experimental-features value

  Set the experimental-features setting.

• --extra-access-tokens value

  Append to the access-tokens setting.

• --extra-allowed-impure-host-deps value

  Append to the allowed-impure-host-deps setting.

• --extra-allowed-uris value

  Append to the allowed-uris setting.

• --extra-allowed-users value

  Append to the allowed-users setting.

• --extra-experimental-features value

  Append to the experimental-features setting.

• --extra-extra-platforms value

  Append to the extra-platforms setting.

• --extra-hashed-mirrors value

  Append to the hashed-mirrors setting.

• --extra-ignored-acls value

  Append to the ignored-acls setting.

• --extra-nix-path value

  Append to the nix-path setting.

• --extra-platforms value

  Set the extra-platforms setting.

• --extra-plugin-files value

  Append to the plugin-files setting.

• --extra-sandbox-paths value

  Append to the sandbox-paths setting.

• --extra-secret-key-files value

  Append to the secret-key-files setting.

• --extra-substituters value

  Append to the substituters setting.

• --extra-system-features value

  Append to the system-features setting.

• --extra-trusted-public-keys value

  Append to the trusted-public-keys setting.

• --extra-trusted-substituters value

  Append to the trusted-substituters setting.

• --extra-trusted-users value

  Append to the trusted-users setting.

• --fallback

  Enable the fallback setting.

• --filter-syscalls

  Enable the filter-syscalls setting.

• --flake-registry value

  Set the flake-registry setting.

• --fsync-metadata

  Enable the fsync-metadata setting.

• --gc-reserved-space value

  Set the gc-reserved-space setting.

• --hashed-mirrors value

  Set the hashed-mirrors setting.

• --http-connections value

  Set the http-connections setting.

• --http2

  Enable the http2 setting.

• --id-count value

  Set the id-count setting.

• --ignore-try

  Enable the ignore-try setting.

• --ignored-acls value

  Set the ignored-acls setting.

• --impersonate-linux-26

  Enable the impersonate-linux-26 setting.

• --keep-build-log

  Enable the keep-build-log setting.

• --keep-derivations

  Enable the keep-derivations setting.

• --keep-env-derivations

  Enable the keep-env-derivations setting.

• --keep-failed

  Enable the keep-failed setting.

• --keep-going

  Enable the keep-going setting.

• --keep-outputs

  Enable the keep-outputs setting.

• --log-lines value

  Set the log-lines setting.

• --max-build-log-size value

  Set the max-build-log-size setting.

• --max-free value

  Set the max-free setting.

• --max-jobs value

  Set the max-jobs setting.

• --max-silent-time value

  Set the max-silent-time setting.

• --min-free value

  Set the min-free setting.

• --min-free-check-interval value

  Set the min-free-check-interval setting.

• --nar-buffer-size value

  Set the nar-buffer-size setting.

• --narinfo-cache-negative-ttl value

  Set the narinfo-cache-negative-ttl setting.

• --narinfo-cache-positive-ttl value

  Set the narinfo-cache-positive-ttl setting.

• --netrc-file value

  Set the netrc-file setting.

• --nix-path value

  Set the nix-path setting.

• --no-accept-flake-config

  Disable the accept-flake-config setting.

• --no-allow-dirty

  Disable the allow-dirty setting.

• --no-allow-import-from-derivation

  Disable the allow-import-from-derivation setting.

• --no-allow-new-privileges

  Disable the allow-new-privileges setting.

• --no-allow-symlinked-store

  Disable the allow-symlinked-store setting.

• --no-allow-unsafe-native-code-during-evaluation

  Disable the allow-unsafe-native-code-during-evaluation setting.

• --no-auto-allocate-uids

  Disable the auto-allocate-uids setting.

• --no-auto-optimise-store

  Disable the auto-optimise-store setting.

• --no-builders-use-substitutes

  Disable the builders-use-substitutes setting.

• --no-compress-build-log

  Disable the compress-build-log setting.

• --no-enforce-determinism

  Disable the enforce-determinism setting.

• --no-eval-cache

  Disable the eval-cache setting.

• --no-fallback

  Disable the fallback setting.

• --no-filter-syscalls

  Disable the filter-syscalls setting.

• --no-fsync-metadata

  Disable the fsync-metadata setting.

• --no-http2

  Disable the http2 setting.

• --no-ignore-try

  Disable the ignore-try setting.

• --no-impersonate-linux-26

  Disable the impersonate-linux-26 setting.

• --no-keep-build-log

  Disable the keep-build-log setting.

• --no-keep-derivations

  Disable the keep-derivations setting.

• --no-keep-env-derivations

  Disable the keep-env-derivations setting.

• --no-keep-failed

  Disable the keep-failed setting.

• --no-keep-going

  Disable the keep-going setting.

• --no-keep-outputs

  Disable the keep-outputs setting.

• --no-preallocate-contents

  Disable the preallocate-contents setting.

• --no-print-missing

  Disable the print-missing setting.

• --no-pure-eval

  Disable the pure-eval setting.

• --no-require-sigs

  Disable the require-sigs setting.

• --no-restrict-eval

  Disable the restrict-eval setting.

• --no-run-diff-hook

  Disable the run-diff-hook setting.

• --no-sandbox

  Disable sandboxing.

• --no-sandbox-fallback

  Disable the sandbox-fallback setting.

• --no-show-trace

  Disable the show-trace setting.

• --no-substitute

  Disable the substitute setting.

• --no-sync-before-registering

  Disable the sync-before-registering setting.

• --no-trace-function-calls

  Disable the trace-function-calls setting.

• --no-trace-verbose

  Disable the trace-verbose setting.

• --no-use-case-hack

  Disable the use-case-hack setting.

• --no-use-cgroups

  Disable the use-cgroups setting.

• --no-use-registries

  Disable the use-registries setting.

• --no-use-sqlite-wal

  Disable the use-sqlite-wal setting.

• --no-warn-dirty

  Disable the warn-dirty setting.

• --plugin-files value

  Set the plugin-files setting.

• --post-build-hook value

  Set the post-build-hook setting.

• --pre-build-hook value

  Set the pre-build-hook setting.

• --preallocate-contents

  Enable the preallocate-contents setting.

• --print-missing

  Enable the print-missing setting.

• --pure-eval

  Enable the pure-eval setting.

• --relaxed-sandbox

  Enable sandboxing, but allow builds to disable it.

• --repeat value

  Set the repeat setting.

• --require-sigs

  Enable the require-sigs setting.

• --restrict-eval

  Enable the restrict-eval setting.

• --run-diff-hook

  Enable the run-diff-hook setting.

• --sandbox

  Enable sandboxing.

• --sandbox-build-dir value

  Set the sandbox-build-dir setting.

• --sandbox-dev-shm-size value

  Set the sandbox-dev-shm-size setting.

• --sandbox-fallback

  Enable the sandbox-fallback setting.

• --sandbox-paths value

  Set the sandbox-paths setting.

• --secret-key-files value

  Set the secret-key-files setting.

• --show-trace

  Enable the show-trace setting.

• --stalled-download-timeout value

  Set the stalled-download-timeout setting.

• --start-id value

  Set the start-id setting.

• --store value

  Set the store setting.

• --substitute

  Enable the substitute setting.

• --substituters value

  Set the substituters setting.

• --sync-before-registering

  Enable the sync-before-registering setting.

• --system value

  Set the system setting.

• --system-features value

  Set the system-features setting.

• --tarball-ttl value

  Set the tarball-ttl setting.

• --timeout value

  Set the timeout setting.

• --trace-function-calls

  Enable the trace-function-calls setting.

• --trace-verbose

  Enable the trace-verbose setting.

• --trusted-public-keys value

  Set the trusted-public-keys setting.

• --trusted-substituters value

  Set the trusted-substituters setting.

• --trusted-users value

  Set the trusted-users setting.

• --use-case-hack

  Enable the use-case-hack setting.

• --use-cgroups

  Enable the use-cgroups setting.

• --use-registries

  Enable the use-registries setting.

• --use-sqlite-wal

  Enable the use-sqlite-wal setting.

• --user-agent-suffix value

  Set the user-agent-suffix setting.

• --warn-dirty

  Enable the warn-dirty setting.