ptx: implement GNU extensions

[ycd]

ptx has -G --traditional flags to specify to whether use traditional mode or GNU extensions, our ptx implementation doesn't supports GNU extensions yet. In traditional mode, there are only several flags available -b, -f, -g, -i, -o, -r, -t and -w, all the other options needs GNU extensions to be implemented.

FLAGS:
    -G, --traditional        behave more like System V 'ptx'

Code is in:
https://github.com/uutils/coreutils/tree/master/src/uu/ptx

GNU's documentation for ptx.

There is also a great documentation available from GNU about: The GNU extensions to ptx.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[chrisdebian]

Tidying up. This is marked as "wontfix"; is that still true? Should this be closed?

Chris

[Misakait]

Hi, I'd like to try working on this issue.

I'm a beginner to open source, so I might take some time to figure things out. I'll be sure to comment again if I get stuck or can no longer work on it.

Thanks for the opportunity!

[chrisdebian]

@Misakait People are usually very welcoming. We just need to be nice to each other :-)

https://opensource.guide/how-to-contribute/

[ChrisDryden]

The GNU extension has been started with a recently merged PR: #9573 for anyone else looking to get started into this

[naoNao89]

The Unknown variant can't be tested via panics. Tests pass with or without it because it's an architectural detail, not a behavioral feature. It matches GNU's logic but doesn't change observable output.

Should we keep it for code clarity or remove it?