I'm trying to do an application that converts applications into daemons (more or less). I basically have several programs (around 10) that are basically console programs with a menu. For example if you press 's' the program will give you statistics. Now I have to run all the programs simultaneously. I would like to have all the programs running as daemons but if I require to "connect" to the programs then I can (maybe by process Id or some other identifier) pipe the current cosole to the specific daemon, as if I'm running that program in the current console. Then I close that connection and I connect to another daemon. I know I can program that into each one of the programs, but I would rather not. I would like not to modifiy the programs at all but have a main program that does something like a popen to each process and then I can redirect those pipes to a console. Somebody knows how can I do that?

Run them is screen sessions. Then you can connect/disconnect/reconnect to them arbitrarily. If you make screen multi-user, you can allow anyone to connect, or a specified selection of users to access the 'daemons'.

man screen

--- rod.

Don't forget that daemons should change their working directory to / so they don't prevent the administrator from un-mounting volumes and so on.

oh, quite simple then?

screen no good?

are they persistent, like overnight, or just while you are logged in and playing with them?

ok, each daemon process starts off and makes a FIFO or named pipe or Unix domain socket,
based on pid, these live in a certain directory, your selector program then can scan the directory
and allow you to choose which process to pipe to.
easy

I'm doing something like that right now. I have this program that creates one thread for each daemon that I have to run. Then I create two pipes and then close(0 and 1) dup2 fork execve. After that each thread creates two named fifos and then they enter in a loop that reads from one of the named fifos and copies into the pipe corresponding to stdin and viceversa. As long as I catch the SIGPIPE signal and I check for the errors it works, but I think is too complicated, I was looking something more obvious like going into /proc/fd and try to replace the symlinks to 0,1,2 (already tried but couldn't make it work). Then I started looking at the source of screen and dtach (similar to screen but simpler) and they basically do something like what I do but using a lot of PTY (that I'm not very familiar with).