I can't use the terminal while gedit command is running

Short Answer

In the unresponsive terminal:

1. Hit Ctrl+Z.
2. Type bg and enter.
3. Type disown and enter.

Long Answer

In the unresponsive terminal, hit Ctrl+Z, this will "pause" the process (or "job") and return the console control to you. However, you'll notice that gedit becomes unresponsive and you can't use it.

Extra: if you want to, you can execute the command jobs, you'll notice that it'll read Stopped for the gedit command, that's why you can't use it.

To make the job successfully run in the background (i.e. to make gedit responsive again), execute the command bg (meaning background). You'll now be able to use gedit, and at the same time have the prompt to yourself.

Extra: now, if you execute jobs, you'll notice that it'll read Running.

You can overcome all of this from the very beginning. When you're launching gedit from the terminal, add an & to the end of the command, so something like this gedit /path/to/file &. This will launch gedit in the background from the first place (you might need to hit Enter a couple of times to get the console control back).

Extra: if you were following these extra notes, you might have noticed that the second time you did jobs, you could see that bash added a & to the end of the gedit command.

Once you get used to this system, you might notice that if you close the terminal, gedit will also terminate, without even a confirmation dialog. To prevent this from happening, run disown, which will detach the gedit process from the terminal, removing it from the list returned by jobs.

Just type:

gedit <filename-to-edit> &

This will immediately return the command prompt to you.

You could use the nohup to prevent the GUI to be attached to a terminal:

nohup mupdf some.pdf &

This will allow you to close the terminal you are launching from, without the program being closed.

You should also notice, that the nohup command will create a file with the stdout and stderr of the command you run. If you want to prevent that, add &>/dev/null before the &.

nohup mupdf some.pdf &>/dev/null &