I am writing automated updaters for certain applications but I don’t want the update to be executed every day. Instead it should only run in case a new version is available. One key component to achieve this is to find out what the latest version is. If a software distributor is using GitHub and if the releases are maintained there the versions can be accessed via API. I wrote a small BaSH snippet to parse the latest version string into a BaSH variable. I demonstrate this I am using the repository of a really great piece of software: Kimai time-tracker. This is a time tracking software I also use for my projects, customers and invoices. It features a well maintained documentations, a great API to connect it to 3rd party applications and a more than usable interface!
TAGNAME=$(curl -H "Accept: application/vnd.github+json" https://api.github.com/repos/kevinpapst/kimai2/releases \ | grep tag_name \ | head -1 \ | sed -E 's/^.*"tag_name": "(.*)",$/\1/g')
So what does this code do? It fetches the releases from the API, looks for lines containing “tag_name” (the member that holds the version number), takes only the first line and extracts the value from the line using sed with a regular expression. The output is assigned to the variable “TAGNAME” and can be used for further evaluation.