$ jekyll build
# The current site folder will be built into the ./_site directory

$ jekyll build --destination /var/www/
# The current site folder will be generated into /var/www/

$ jekyll build --watch
# The current site folder will be built into the ./_site directory and will be kept up to date with the source until you press CTRL+C to kill the process

you can set a Jekyll environment and value, when build time

JEKYLL_ENV=production jekyll b

JEKYLL_ENV=production jekyll build

JEKYLL_ENV=production bundle exec jekyll build

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if your code contains the bellow snippet, analytics.html will not be included unless your building with JEKYLL_ENV=production

{% if jekyll.environment == "production" %}

   {% include analytics.html %}

{% endif %}