https://github.com/brho/plan9/blob/89d43d2262ad43eb4b26c2a8d... seems to be a global variable. https://9fans.github.io/plan9port/man/man3/arg.html also references it.

Used by sysfatal(2):

https://github.com/0intro/plan9-contrib/blob/master/sys/src/...

Also mentioned in sysfatal(2)'s manual:

http://man.cat-v.org/9front/2/perror

Also used in the beautiful (for those who like being creative with the preprocessor) options parser https://9fans.github.io/plan9port/man/man3/arg.html

Thank you, that bit was very interesting. I like the idea for single threaded applications of having argv0 be a global.

Doesn't have to be single-threaded even. Main writes the pointer at the start, and no one else is going to change it, just read from it.

The plan9 one is short and sweet, but what I don't like is that it doesn't support the dashdash thing that unambiguously marks that rest of the arguments should be interpreted as files and not flags. Needed for reliable defensive shell scripts imo.

You may say "it has no options anyway" but other cats do. And you may want to add options in a future version.

I thought that’s a GNU-ism that wasn’t in POSIX, but https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1... taught me differently.

Now I think it made it into POSIX only fairly recently (corrections welcome)

(it is a good idea, though)