Re: Setting $0 clears /proc/PID/environ too

The problem is that the process name and /proc/PID/environ are actually windows into the address space of the process. The pointers that determine these windows are in the kernel and the program cannot update them, but you can change the data stored in the region they point to.

Does changing $0 destroy %ENV or does perl copy the environment out of the way before reusing the original environment block?

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Re^2: Setting $0 clears /proc/PID/environ too by kikuchiyo (Hermit) on Jan 17, 2020 at 09:39 UTC
Does changing $0 destroy %ENV or does perl copy the environment out of the way before reusing the original environment block? No, that happens very early, so even BEGIN blocks have %ENV correctly filled, and in any case later changes to %ENV are not reflected in /proc/PID/environ. That file is more like a historical record of what the environment was when the process started, and as such, it has potential (if marginal) uses, and that's why this bothers me.	[reply]

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Re^2: Setting $0 clears /proc/PID/environ too
by kikuchiyo (Hermit) on Jan 17, 2020 at 09:39 UTC

Does changing $0 destroy %ENV or does perl copy the environment out of the way before reusing the original environment block?

No, that happens very early, so even BEGIN blocks have %ENV correctly filled, and in any case later changes to %ENV are not reflected in /proc/PID/environ. That file is more like a historical record of what the environment was when the process started, and as such, it has potential (if marginal) uses, and that's why this bothers me.

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