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  • Interesting demo of env producing these environment strings when fed an arg that contains a newline in the right place. (Which is possible even with shells that don't support $'escape sequences'). Unless env could (or POSIXly should?) be doing any filtering itself? Otherwise should be possible with just a POSIX shell environment, no compiler other other programming languages needed. (It's still not directly from sh, which is what the question asked about; good data points on that, too.) Commented Sep 8 at 6:27
  • Didn't do what? AFAICT, zsh doesn't strip the env vars it can't import as shell variables either. Note that bash sets variables with %% in their name since shellshock for its exported functions, so it would be silly if it did this kind of thing. Commented Sep 8 at 6:51
  • @PeterCordes, mm, the post says "could an implementation of POSIX sh keep invalid names in the environment that it executes utilities under?" and I read that as asking if it's possible for a program launched from a POSIX-like shell to receive envvars with funny names, in some way, regardless of how they came to be. Commented Sep 8 at 10:04
  • @StéphaneChazelas, I don't know what zsh is supposed to do, but at least with that simple test, zsh didn't pass through the envvar with the funny name. Commented Sep 8 at 10:05
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    @StéphaneChazelas, ok, right, I only tried the zsh on my mac (zsh 5.9 (x86_64-apple-darwin23.0)) at first, I should have mentioned that. The behaviour looks to be different there vs. on Ubuntu, so I suppose it might be some Apple-specific modification(?) Commented Sep 8 at 12:29