Ruby Sass Command-Line Interface

⚠️ Heads up!

Ruby Sass has reached end of life and is now totally unmaintained. Please switch to Dart Sass or LibSass at your earliest convenience.

Usage permalinkUsage

The Ruby Sass executable can be invoked in one of two modes.

One-to-One Mode permalinkOne-to-One Mode

sass [input.scss] [output.css]

One-to-one mode compiles a single input file (input.scss) to a single output location (output.css). If no output location is passed, the compiled CSS is printed to the terminal. If no input or output is passed, the CSS is read from standard input and printed to the terminal.

The input file is parsed as SCSS if its extension is .scss or as the indented syntax if its extension is .sass. If it doesn’t have one of these two extensions, or if it comes from standard input, it’s parsed as the indented syntax by default. This can be controlled with the --scss flag.

Many-to-Many Mode permalinkMany-to-Many Mode

sass [<input.css>:<output.css>] [<input/>:<output/>] [input.css] [input/]...

Many-to-many mode compiles one or more input files to one or more output files. The inputs are separated from the outputs with colons. It can also compile all Sass files in a directory to CSS files with the same names in another directory. Many-to-many mode is enabled when any argument contains a colon, or when the --update flag or the --watch flag is passed.

If an input file is passed without a corresponding output file, it’s compiled to a CSS file named after the input file, but with the extension replaced with .css. If an input directory is passed without a corresponding output directory, all the Sass files within it are compiled to CSS files in the same directory.

$ sass style.scss:style.css
      write style.css
$ sass light.scss:light.css dark.scss:dark.css
      write light.css
      write dark.css
$ sass themes:public/css
      write public/css/light.css
      write public/css/
      write public/css/dark.css
      write public/css/

When compiling whole directories, Sass will ignore partial files whose names begin with _. You can use partials to separate out your stylesheets without creating a bunch of unnecessary output files.

Many-to-many mode will only compile stylesheets whose dependencies have been modified more recently than the corresponding CSS file was generated. It will also print status messages when updating stylesheets.

Options permalinkOptions

Common permalinkCommon

–load-path permalink--load-path

This option (abbreviated -I) adds an additional load path for Sass to look for stylesheets. It can be passed multiple times to provide multiple load paths. Earlier load paths will take precedence over later ones.

$ sass --load-path=node_modules/bootstrap/dist/css style.scss style.css

Load paths are also loaded from the SASS_PATH environment variable, if it’s set. This variable should be a list of paths separated by ; (on Windows) or : (on other operating systems). Load paths on SASS_PATH take precedence over load paths passed on the command line.

$ SASS_PATH=node_modules/bootstrap/dist/css sass style.scss style.css

–require permalink--require

This option (abbreviated -r) loads a Ruby gem before running Sass. It can be used to load functions defined in Ruby into your Sass environment.

$ sass --require=rails-sass-images style.scss style.css

–compass permalink--compass

This flag loads the Compass framework and makes its mixins and functions available for use in Sass.

$ sass --compass style.scss style.css

–style permalink--style

This option (abbreviated -t) controls the output style of the resulting CSS. Ruby Sass supports four output styles:

  • nested (the default) indents CSS rules to match the nesting of the Sass source.
  • expanded writes each selector and declaration on its own line.
  • compact puts each CSS rule on its own single line.
  • compressed removes as many extra characters as possible, and writes the entire stylesheet on a single line.
$ sass --style=nested
h1 {
  font-size: 40px; }
  h1 code {
    font-face: Roboto Mono; }

$ sass --style=expanded style.scss
h1 {
  font-size: 40px;
h1 code {
  font-face: Roboto Mono;

$ sass --style=compact style.scss
h1 { font-size: 40px; }
h1 code { font-face: Roboto Mono; }

$ sass --style=compressed style.scss
h1{font-size:40px}h1 code{font-face:Roboto Mono}

–help permalink--help

This flag (abbreviated -h and -?) prints a summary of this documentation.

$ sass --help
Usage: sass [options] [INPUT] [OUTPUT]

  Converts SCSS or Sass files to CSS.


–version permalink--version

This flag prints the current version of Sass.

$ sass --version

Watching and Updating permalinkWatching and Updating

These options affect many-to-many mode.

–watch permalink--watch

Enables many-to-many mode, and causes Sass to stay open and continue compiling stylesheets whenever they or their dependencies change.

$ sass --watch themes:public/css
      write public/css/light.css
      write public/css/

​# Then when you edit themes/dark.scss...
      write public/css/dark.css
      write public/css/

–poll permalink--poll

This flag, which may only be passed along with --watch, tells Sass to manually check for changes to the source files every so often instead of relying on the operating system to notify it when something changes. This may be necessary if you’re editing Sass on a remote drive where the operating system’s notification system doesn’t work.

$ sass --watch --poll themes:public/css
      write public/css/light.css
      write public/css/

​# Then when you edit themes/dark.scss...
      write public/css/dark.css
      write public/css/

–update permalink--update

This flag enables many-to-many mode, even if none of the arguments are colon-separated pairs.

$ sass --update style.scss
      write style.css

–force permalink--force

This flag (abbreviated -f) may only be passed in many-to-many mode. It causes Sass files to always be compiled to CSS files, instead of only being compiled when the source files are more up-to-date than the output.

The --force flag may not be passed alongside the --watch flag.

$ sass --force style.scss:style.css
      write style.css

–stop-on-error permalink--stop-on-error

This flag may only be passed in many-to-many mode. It tells Sass to stop compiling immediately when an error is detected, rather than trying to compile other Sass files that may not contain errors.

$ sass --stop-on-error themes:public/css
Error: Invalid CSS after "h1 {font-size: ": expected expression (e.g. 1px, bold), was "}"
        on line 1 of test.scss
  Use --trace for backtrace.

Input and Output permalinkInput and Output

These options control how Sass loads its input files and how it produces output files.

–scss permalink--scss

This flag tells Sass to parse standard input as SCSS.

$ echo "h1 {font-size: 40px}" | sass --scss
h1 {
  font-size: 40px;

–sourcemap permalink--sourcemap

This option controls how Sass generates source maps, which are files that tell browsers or other tools that consume CSS how that CSS corresponds to the Sass files from which it was generated. They make it possible to see and even edit your Sass files in browsers. See instructions for using source maps in Chrome and Firefox. It has four possible values:

  • auto (the default) uses relative URLs to link from the source map to the Sass stylesheets where possible, and absolute file: URLs otherwise.
  • file always uses absolute absolute file: URLs to link from the source map to the Sass stylesheets.
  • inline includes the text of the Sass stylehseets in the source map directly.
  • none doesn’t generate source maps at all.
​# Generates a URL like "../sass/style.scss".
$ sass --sourcemap=auto sass/style.scss css/style.css

​# Generates a URL like "file:///home/style-wiz/sassy-app/sass/style.scss".
$ sass --sourcemap=file sass/style.scss css/style.css

​# Includes the full text of sass/style.scss in the source map.
$ sass --sourcemap=inline sass/style.scss css/style.css

​# Doesn't generate a source map.
$ sass --sourcemap=none sass/style.scss css/style.css

–stdin permalink--stdin

This flag (abbreviated -s) is tells Sass to read its input file from standard input. When it’s passed, no input file may be passed.

$ echo -e 'h1\n  font-size: 40px' | sass --stdin
h1 {
  font-size: 40px;

The --stdin flag may not be used with many-to-many mode.

–default-encoding permalink--default-encoding

This option (abbreviated -E) controls the default character encoding that Sass will use to load source files that don’t explicitly specify a character encoding. It defaults to the operating system’s default encoding.

$ sass --default-encoding=Shift-JIS style.scss style.css

–unix-newlines permalink--unix-newlines

This flag tells Sass to generate output files with whose lines are separated with the U+000A LINE FEED character, as opposed to the operating system default (on Windows, this is U+000D CARRIAGE RETURN followed by U+000A LINE FEED). It’s always true on systems that default to Unix-style newlines.

$ sass --unix-newlines style.scss style.css

–debug-info permalink--debug-info

This flag (abbreviated -g) causes Sass to emit dummy @media queries that indicate where each style rule was defined in the source stylehseet.

⚠️ Heads up!

This flag only exists for backwards-compatibility. Source maps are now the recommended way of mapping CSS back to the Sass that generated it.

$ sass --debug-info style.scss
@media -sass-debug-info{filename{font-family:file\:\/\/\/home\/style-wiz\/sassy-app\/style\.scss}line{font-family:\000031}}
h1 {
  font-size: 40px; }

–line-comments permalink--line-comments

This flag (also available as --line-numbers, abbreviated as -l) causes Sass to emit comments for every style rule that indicate where each style rule was defined in the source stylesheet.

$ sass --line-numbers style.scss
/* line 1, style.scss */
h1 {
  font-size: 40px; }

Other Options permalinkOther Options

–interactive permalink--interactive

This flag (abbreviated -i) tells Sass to run in interactive mode, where you can write SassScript expressions and see their results. Interactive mode also supports variables.

$ sass --interactive
>> 1px + 1in
>> $map: ("width": 100px, "height": 70px)
("width": 100px, "height": 70px)
>> map-get($map, "width")

–check permalink--check

This flag (abbreviated -c) tells Sass to verify that the syntax of its input file is valid without executing that file. If the syntax is valid, it exits with status 0. It can’t be used in many-to-many mode.

$ sass --check style.scss

–precision permalink--precision

This option tells Sass how many digits of precision to use when emitting decimal numbers.

$ echo -e 'h1\n  font-size: (100px / 3)' | sass --precision=20
h1 {
  font-size: 33.333333333333336px; }

–cache-location permalink--cache-location

This option tells Sass where to store its cache of parsed files, so it can run faster in future invocations. It defaults to .sass-cache.

$ sass --cache-location=/tmp/sass-cache style.scss style.css

–no-cache permalink--no-cache

This flag (abbreviated -C) tells Sass not to cache parsed files at all.

$ sass --no-cache style.scss style.css

–trace permalink--trace

This flag tells Sass to print the full Ruby stack trace when an error is encountered. It’s used by the Sass team for debugging errors.

Traceback (most recent call last):
        25: from /usr/share/gems/sass/bin/sass:13:in `<main>'
        24: from /usr/share/gems/sass/lib/sass/exec/base.rb:18:in `parse!'
        23: from /usr/share/gems/sass/lib/sass/exec/base.rb:50:in `parse'
        22: from /usr/share/gems/sass/lib/sass/exec/sass_scss.rb:63:in `process_result'
        21: from /usr/share/gems/sass/lib/sass/exec/sass_scss.rb:396:in `run'
        20: from /usr/share/gems/sass/lib/sass/engine.rb:290:in `render'
        19: from /usr/share/gems/sass/lib/sass/engine.rb:414:in `_to_tree'
        18: from /usr/share/gems/sass/lib/sass/scss/parser.rb:41:in `parse'
        17: from /usr/share/gems/sass/lib/sass/scss/parser.rb:137:in `stylesheet'
        16: from /usr/share/gems/sass/lib/sass/scss/parser.rb:697:in `block_contents'
        15: from /usr/share/gems/sass/lib/sass/scss/parser.rb:707:in `block_child'
        14: from /usr/share/gems/sass/lib/sass/scss/parser.rb:681:in `ruleset'
        13: from /usr/share/gems/sass/lib/sass/scss/parser.rb:689:in `block'
        12: from /usr/share/gems/sass/lib/sass/scss/parser.rb:697:in `block_contents'
        11: from /usr/share/gems/sass/lib/sass/scss/parser.rb:708:in `block_child'
        10: from /usr/share/gems/sass/lib/sass/scss/parser.rb:743:in `declaration_or_ruleset'
         9: from /usr/share/gems/sass/lib/sass/scss/parser.rb:820:in `try_declaration'
         8: from /usr/share/gems/sass/lib/sass/scss/parser.rb:1281:in `rethrow'
         7: from /usr/share/gems/sass/lib/sass/scss/parser.rb:807:in `block in try_declaration'
         6: from /usr/share/gems/sass/lib/sass/scss/parser.rb:999:in `value!'
         5: from /usr/share/gems/sass/lib/sass/scss/parser.rb:1161:in `sass_script'
         4: from /usr/share/gems/sass/lib/sass/script/parser.rb:68:in `parse'
         3: from /usr/share/gems/sass/lib/sass/script/parser.rb:855:in `assert_expr'
         2: from /usr/share/gems/sass/lib/sass/script/lexer.rb:240:in `expected!'
         1: from /usr/share/gems/sass/lib/sass/scss/parser.rb:1305:in `expected'
test.scss:1: Invalid CSS after "h1 {font-size: ": expected expression (e.g. 1px, bold), was "}" (Sass::SyntaxError)

–quiet permalink--quiet

This flag (abbreviated -q) tells Sass not to emit any warnings when compiling. By default, Sass emits warnings when deprecated features are used or when the @warn rule is encountered. It also silences the @debug rule.

$ sass --quiet style.scss style.css