In plan9 cat is "argv0" correct? about cats

[pete]

It was correctly copied, and it is used, but the usage isn't readily apparent. The declaration of argv0 as a global is in libc.h (https://github.com/0intro/plan9/blob/master/sys/include/libc.h#L718), and sysfatal makes use of it for its error message. Other programs in Plan 9 use it in place of argv[0] for scope convenience, and it often gets assigned like argv0 = argv[0]. (Just a WAG, but I'd speculate that having it as a global also helps with identifying random core files.) There is some slightly more involved usage of argv0 (e.g., https://github.com/0intro/plan9/blob/master/sys/src/cmd/aux/usage.c) but it's usually just set at the beginning and then not explicitly used.

I don't have the exact history handy (you might want to try 9fans) but it doesn't seem to appear in the fabled (and only recently released) Unix Research Version 10 libc (https://www.tuhs.org/Archive/Distributions/Research/Dan_Cross_v10/ has tarballs), though there's some usage of argv0 resembling Plan 9's usage in the interactive SCSI shell for the WORM system.

If you aren't able to check out the source code, you can find it in @0intro's Plan 9 repo here: https://github.com/0intro/plan9/blob/master/sys/src/cmd/cat.c. The 9front version (http://code.9front.org/hg/plan9front/file/8ae76288951f/sys/src/cmd/cat.c) and the P9P version (https://9fans.github.io/usr/local/plan9/src/cmd/) are identical.

[Gumnos]

Ah, okay. Just seemed odd but your explanation makes it less strange. Thanks.