Dear all,

Stefan wants to run an external EPICS driver process as a detached process and somehow "glue" it to midas to control it. Actually a similar requirement led to the development of MIDAS in the '90s. We had too many configuration files lying around, to many process to control and interact together with each other and so on. With the development of MIDAS I wanted to integrate all that. There is one ODB to control an parasitize everything, one central process handling to see if processes are alive, raise an alarm if they die, automatically restart them if necessary and so on. Doing this now externally again is orthogonal to the original design concept of MIDAS and will cause many problems. I therefore strongly recommend to to juggle around with systemctl and syslog, but to make everything a MIDAS process. It's simply a "cm_connect_experiment()" and "cm_disconnect_experiment()" in the end. Then you set

/programs/requited = y

and

/programs/start command = <cmd>

You can set the "alarm class" to raise an alarm if the program crashes, and you will see all messages if you use "cm_msg()" inside the program rather than "printf()". Injecting a separate .log file into the system will show things on the message page, but these messages do not go through the SYSMSG buffer, and cannot received by other programs. Maybe you noticed that mhttpd on the status page always shows the last message it received, which can be very helpful. To see if a program is running, you only need a cm_exist() call, which also exists for custom web pages.

Rather than investing time to re-invent the wheel here, better try to modify your EPICS driver process to become a midas process.

If you have an external process which you absolutely cannot modify, I would rather write a wrapper midas program to start the external process, intercept it's output via a pipe, and put its output properly into the midas message system with cm_msg(). In the main loop of your wrapper function you check the external process via whatever you want, and if it dies trigger an alarm or restart it from your wrapper program. You can then set an alarm on your wrapper program to make sure this one is always running.

Best regards,
StefanR