This crate provides a mechanism to tweak environment variables
within a child subprocess dynamically without the subprocess
needing to know anything about it. To do this, we build a
.so file that registers a startup hook and launches a background
thread listening on a control unix socket. The parent process
can then dial in to the control socket, authenticate, and
then place an RPC call to setenv. Since the syscall is invoked
in the victim child process, the child's environment changes
on the fly.
This crate was developed in service of the shpool tool, but
it is a general tool so it is split out into its own crate.
subprocess-inject-env is known to work on linux.