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Append hash to asset in hugo

Vinh  hugo asset perf

Hugo doesn’t has a built-in process to append a revision/hash to asset file name when compile from the theme. As the result, the URL remains same and is cached in browser unless we explicitly trigger force refresh. If we could append the hash, we can let browser caches it forever hence improve site performance.

This is what I setup to achieve this for axcoto.com with a simple bash script. It isn’t scale way but it’s a good start when we just need to whip up something.

Our goal: instead of css/main-4d71a5581e0393ddfc00249554fd4fa9.css we now have css/main-md5-hash-here.css.

I put this in my makefile

CSS_DIR = public/css
CSS_FILE = $(CSS_DIR)/main.css
CSS_REV = main-$(shell md5 -r $(WORKDIR)/$(CSS_FILE) | awk '{print $$1}').css

  cp $(CSS_FILE) "$(CSS_DIR)/main-$(shell md5 -r $(CSS_FILE) | awk '{print $$1}').css"
  find public -name "*.html" -print0 | xargs -0 -I filename /bin/bashh -c "echo filename; sed 's/css\/main.css/css\/$(CSS_REV)/g' filename > tmp; mv tmp filename"

We simply copy the css file and append the md5 hash. We have to redirect output of sed since I don’t know a way to replace inline with sed on Mac.

Now, after generate content, we simply run:

make asset

It find all .html file and replace path of css/main-4d71a5581e0393ddfc00249554fd4fa9.css with the hash appended.