a memo on argument parsing

# p7zip

p7zip is a port of 7z (a rare piece of free software for windows) to UNIX systems.

like 7z, p7zip uses “function letters”, this means stuff like extract, add, delete, list is done as a command, without a - at the front of the letter.

Extracting can be done with:

$ 7z x <input> -o <output>

The x makes sense—it’s one of many actions in the action tree. This style is popular, e.g. tailscale status or docker network ls.

# tar

tar uses switches and allows both single - for “UNIX-style” and -- for “GNU-style”

Extracting can be done with:

$ tar -xf <input> <output>

# OR

$ tar --extract <input> <output>

But it also works if you omit the switches. It’s kinda confusing but that’s how it is. At least it’s consistent with forcing everything to be switches.

Even though it’s less intuitive than the “action-first” approach, it’s arguably easier to implement and more consistent; we don’t have to guess if a thing is an action or an option. Although surely that’s obvious? Not quite, we can use docker container ls for listing containers but then it’s playerctl -l for listing available mpris2 players. Both have command-like invocations and switches. Maybe it’s easier to just do one or the other.