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

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.