How to exit a process after disown

Question

I use disown to run long-running process via SSH. For example I run the following program:

vmd -e script.tcl > out.txt &

Then I use disown -a to deattach it from the shell. When I reconnect the terminal the out.txt shows that the program has finished. However, it shows the command prompt of the vmd (vmd>). VMD is a program for running TCL scripts for chemistry simulations. You can assume it is something like python with its own shell

http://www.ks.uiuc.edu/Training/Tutorials/vmd/tutorial-html/node8.html

After a while, I couldn't connect to ssh because of the limit on the running processes (fork retry: Resource temporary unavailable). First, I want to know how I can kill those disowned processes if they are in waiting state.

Second, I want to know if I exit the vmd program by putting exit at the end of my script.tcl, would it resolve the problem above for future uses?

Answer 1

There Is More Than One Way To Do It. (TM)

Solution 1 (probably the best): add the command to exit vmd to the end of your script.

Solution 2: redirect standard input of the vmd command to (or from, depending on your mindset) the null device, like so:

vmd -e script.tcl > out.txt < /dev/null &

That way when vmd is done with your script and tries to read the next command from standard input it will receive "end of file" and exit.

Solution 3: Kill the left over vmd process with kill. You'll need its PID for that which you can either note as the shell prints it after starting it with &, or find through the command ps ax. Try kill -TERM (the default) first, if that doesn't work use kill -HUP. Do not use kill -KILL aka kill -9.

Solution 4: Use screen or tmux instead of disown. That way you can reconnect to the running vmd process and enter further commands like exit.