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Hey Unix history nerds:

Do we know who wrote tar(1)? Like, the original tar.c included in V7 Research Unix (which is the earliest one I can find). The list of potential culprits is pretty short, but there's no attribution I can find.

(If you have an answer, please clarify where you got it from, and reference any contemporaneous/primary sources if you've got them.)

@piggo @joe from what I can tell:

98% of C programmers misunderstand how switch works.

2% of C programmers still misunderstand it, but have learned some Dumb Switch Tricks (I'm in this category).

@joe this has strong Duff's Device energy.

Well! I've definitely seen my share of "idiosyncratic" C styles omitting braces and exploiting corner cases in 30+ years of having to read other peoples' C code, but this is a new one.

I had not thought about what would happen if you left the braces off a switch. Because, of course, doing so would be utterly unhinged.

I give you: the world's most obtuse version of "if (x == A || x == b)", indistinguishable from an editing mistake.

Many Unix tar programs leak uninitialized data into unused portions of the file. This is not unusual for C programs (unfortunately). The leaked data is usually just repetition of earlier files, so it wasn't obviously useful for anything.

Until I noticed that optimizations to tar programs tended to change _which_ earlier data was leaked.

Turns out, you can use this behavior to fingerprint the tar implementation pretty precisely in some cases.