Start background process/daemon from CGI script

Question

I\'m trying to launch a background process from a CGI scripts. Basically, when a form is submitted the CGI script will indicate to the user that his or her request is being

Answer 1

There are situations where passing work off to a daemon or cron is not appropriate. Sometimes you really DO need to fork, let the parent exit (to keep Apache happy) and let something slow happen in the child.

What worked for me: When done generating web output, and before the fork:

fflush(stdout), close(0), close(1), close(2); // in the process BEFORE YOU FORK

Then fork() and have the parent immediately exit(0);

The child then AGAIN does close(0), close(1), close(2); and also a setsid(); ...and then gets on with whatever it needs to do.

Why you need to close them in the child even though they were closed in the primordial process in advance is confusing to me, but this is what worked. It didn't without the 2nd set of closes. This was on Linux (on a raspberry pi).