linux

In general you can examine the output of ps x. Either there is run.sh there or not. If there is, it may be the process you seek or some other run.sh. Further investigation may be required.

There is however this trick. Note nohup prints a message like this:

nohup: ignoring input and appending output to /home/alli/nohup.out

Now invoke:

lsof /home/alli/nohup.out

If your run.sh invoked with nohup is still running, it should appear in the output of lsof (twice, because nohup redirects file descriptor 1 and 2 to nohup.out). If you used nohup more than once, lsof should return multiple processes. If you used nohup more than once with the same executable, you may need to check /proc/$pid/ (example) to tell them apart.

I would use tmux in the first place. In fact I do use it on a daily basis.