More portable extraction of short hostname

[jasontedor]

This commit increases the portability of extracting the short hostname
on a Unix-like system.

Closes #13107

[nik9000]

This probably deserves a comment or some helpful person will revert it back to hostname -s. Which unices don't have -s, btw?

[nik9000]

This probably deserves a comment or some helpful person will revert it back to hostname -s. Which unices don't have -s, btw?

This probably deserves a comment or some helpful person will revert it back to hostname -s. Which unices don't have -s, btw?

Ah. Solaris 10.

[nik9000]

Otherwise LGTM.

[jasontedor]

@nik9000 Also HP-UX.

I've added a comment as you requested. I also discovered in the course of testing this is on Solaris VM that combining the variable definition and export into a single line isn't supported in some shells (namely the Bourne shell which is the default shell on Solaris). I've found a more portable way to do the export as well. I've updated the pull request accordingly.

[nik9000]

I've found a more portable way to do the export as well. I've updated the pull request accordingly.

Bleh. I'm not against just using #!/bin/bash instead of #!/bin/sh.

Thanks for adding the comment - that is perfect.

[jasontedor]

I'm not against just using #!/bin/bash instead of #!/bin/sh.

@nik9000 I've been contemplating that as well but at a minimum it is a separate issue from this one.

[nik9000]

@nik9000 I've been contemplating that as well but at a minimum it is a separate issue from this one.

Yeah, probably.