There is some difference between free-style project shell build step and the pipeline `sh` step. If I set in jenkins global configuration `bash` as the "Shell Executable", then free-style project works and calls `bash` from the PATH on the slave. The pipeline `sh` step fails like this though:

[pipeline-test-job] Running shell script
sh: /home/jenkins/workspace/pipeline-test-akostadi@tmp/durable-2ff6e6ae/script.sh: bash: bad interpreter: No such file or directory
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
ERROR: script returned exit code 126
Finished: FAILURE

The use case is that some systems like MacOS ship with an old bash version under /bin/sh. And we want to not be limited in shell scripts by that version. Since proper bash should be installed in other locations on such slaves, we need to run `bash` from PATH. But also can't hardcode `bash` absolute path because it is still `/bin/bash` on normal linux slaves.

I'm reading through ShellStep.java and BourneShellScript.java.

It looks like it launches `sh -c cmd` but I don't see how the global setting is applied, even less I understand why it fails. At the same time free-style projects work fine with this setting on all slaves.

I think this difference between free-style and pipeline might be related to JENKINS-44341 also.

Any clue what exactly might be the difference and how it could be fixed?