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Yes the proper way to do that is execve, not by changing global variables in your parent process. https://man7.org/linux/man-pages/man2/execve.2.html

Using setenv is mostly always a hack that relies on a bunch of assumptions that could easily change and be hard to debug.

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Unless there is a fork exec family of syscalls are not child processes but the same process itself. Small detail but important because sometimes you really want a separate process altogether.

in that case you do not need setenv to pass values to the underlying process though. And if you are forking without immediately execv in a multithreaded program, setenv is the last of your problems.

edit: what's probably happening is that execve is four or five abstraction layers deeper (possibly in a third party dependency) than where the env variable need to be set without a clean way to pass the values through.

The likely scenarios I was thinking (setenv vs execve) would both be called in the child process after fork. But of course here we get to the fascinating world of fork interactions with threads, and you could even have one thread fork()ing while another thread is doing a setenv().

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