cssnano-cli 
A CLI for modular minifier cssnano.
With npm do:
npm install cssnano-cli --global
You can also install cssnano-cli as a development dependency of your project, and get the command by this snippet in your .bashrc:
export PATH=$PATH:./node_modules/.bin
$ cssnano --help
Usage: cssnano [input] [output] {OPTIONS}
Options:
--sourcemap, -s Generate a sourcemap within the minified output.
--no-[featureName] Disable any individual processor module by its name.
[featureName] can be any one of these:
autoprefixer filterOptimiser normalizeUrl
calc filterPlugins orderedValues
colormin functionOptimiser reduceIdents
convertValues mergeIdents singleCharset
core mergeLonghand styleCache
discardComments mergeRules svgo
discardDuplicates minifyFontValues uniqueSelectors
discardEmpty minifyParams zindex
discardUnused minifySelectors
--safe Disable advanced optimisations that are not always safe.
Currently, this disables custom identifier reduction,
z-index rebasing, unused at-rule removal & conversion
between absolute length values.
--version, -v Outputs the version number.
--help, -h Outputs this help screen.
You can also use stdin & stdout redirections:
cssnano < main.css > main.min.css
Pull requests are welcome. If you add functionality, then please add unit tests to cover it.
MIT © Ben Briggs