Unset environment variable

Learning
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Hello, everybody :wave:

Is it possible somehow to unset (remove) environment variable after it was set with Unix.putenv? Maybe I miss something, but I do not see any suitable function for this task in Stdlib :frowning:

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Indeed, I believe this function does not exist in the standard library at the moment. It could be a nice addition.

Cheers,
Nicolas

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  1. there’s a unsetenv(3) function, so unless there’s a good argument, I don’t quite see why there isn’t a wrapper in the unix library. But maybe I’m missing something.
    2. I wanted to suggest that you could just supply a full environment to unix execve, but then, it seems there’s no way to get a full environment list either (?)

Yeah, this seems like a real problem. Also, really easy to fix. Unless somebody else wants to just hack up a patch, I’ll do right now. Maybe I’ll learn that there’s an incompatibility issue I don’t understand. Hey, it’ll be an adventure!

Oh, there’s Unix.environment() which returns the environment, and then you can pass it to Unix.execve(). I retract my previous comment.

ETA: I don’t mean to suggest that this is a solution to your problem, but rather, a workaround.

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FWIW there is (among others) unsetenv in ExtUnix.

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With the advent of OCaml 5.0, adding a thread-broken function to the standard library seems a bit short-sighted. In fact, it might be worth considering the removal of Unix.putenv altogether.

The majority of uses of putenv/unsetenv can be adequately replaced by calls to execve. The only use case that is not covered by execve, as far as I know, is when you want to communicate with a linked library through the putenv/getenv covert channel.

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And the use-case of getting times in different timezones by setting the TZ variable.

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There was an attempt to add Unix.unsetenv together with Unix.setenv, but it was not merged because of concerns about the semantics of Unix.setenv. IMO Unix.unsetenv by itself should be uncontroversial.