This hungry bot searches websites of restaurants around TU Wien and tells you all possible lunch menus.

First, you need to create a slack app (follow this instruction). Then, create a config file that contains the Bot User OAuth Access Token. The config file can also contain an array of restaurants with URL and a xpath and a day offset to each menu they provide. An example config file can be generated like this:

cat > config.yaml << EOF
SLACK_BOT_TOKEN: xoxb-0123456789ab-0123456789ab-0123456789abcdefghijklmn

restaurants:
    - name: Mensa
      url: 'http://menu.mensen.at/index/index/locid/9'
      menus:
          - xpath: '//div[{}]/div[2]/div[1]/div[6]/p/strong/text()'
            day_offset: 1
          - xpath: '//div[{}]/div[2]/div[2]/div[6]/p/strong/text()'
            day_offset: 1
          - xpath: '//div[{}]/div[2]/div[3]/div[6]/p/strong/text()'
            day_offset: 1
EOF

It parses the TU Wien Freihaus Mensa and posts the three daily menus in the chat.