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unixjenkinsjenkins-pipeline
B.T Anand
B.T Anand

Reputation: 617

Jenkins Predefined environment variables

It is interesting that we must have used Jenkins predefined build environment variables like $WORKSPACE, $BUILD_NUMBER etc in a lot of our Jenkins job.

I find it boggling to understand that, how does Jenkins set rules such that when we print $WORKSPACE, it prints the current workspace of various jobs. How does it map the variable $WORKSPACE to the corresponding Jenkins Job.

Upvotes: 0

Views: 11073

Answers (1)

Michael Powers
Michael Powers

Reputation: 2050

Jenkins needs to know certain things about your build environment and jobs in order to do its job properly. For instance it needs to know the current build number, the location where your project should be checked out, who started the current build, etc. These things are typically exposed to you through the web interface.

Jenkins also exposes this information to your build scripts through environment variables that are injected into your scripts by Jenkins when your it is first launched. These environment variables can then be picked up by your script to do whatever is necessary with them.

In the example you gave ($WORKSPACE) Jenkins needs to know the absolute path to this location on your build slave because if it didn't, it wouldn't be able to check out your source and build it. Since it knows this information it exposes it to you as well to make writing your scripts easier.

There's a complete list of generally available environment variables provided by Jenkins available here.

Upvotes: 2

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