[tremon]

Frankly, I think it is idiotic to require each program to parse an environment variable, open that named file, write a magic string, and all the error handling that that requires -- all for the purpose of having a backchannel between the daemon and its supervisor?

Compare with how s6 does the same thing: instead of passing a random path via an environment variable, it opens the file descriptor itself before exec()ing the binary. All the binary has to do is write a newline to that fd and close it.

No 50 lines of C code needed.