Custom hotkey/shortcut to open/bring to front an app

The wmctrl program is just what you're looking for (sudo apt-get install wmctrl). You can use the wmctrl -a "AppTitle" command to bring the app to the front. wmctrl -l will list all available windows, so it should be easy to write a shell script that checks if your program is running and either launches it or brings it to the front. Then you can just bind that to a keyboard shortcut.

First save the following script somewhere, I'll use /home/jtb/code/bringToFront. It takes two arguments, the first is what you would type at the terminal to launch the program, the second is a substring of the program window's title. If there is no constant unique string in the title then you'll need to do a bit more work to find the program's window.

#!/bin/bash
if [ `wmctrl -l | grep -c "$2"` != 0 ]  
then
    wmctrl -a "$2"
else
    $1 &
fi

2. With the script in your current directory, run chmod +x bringToFront to make the script executable. Then make sure it works; to launch/focus firefox you could run ./bringToFront firefox "Mozilla Firefox".

3. Now we need to bind a shortcut key. Run gconf-editor and navigate the folder structure to the left to /apps/metacity/keybinding_commands.

4. Double click on the first command with a blank value, probably command_1. Type the full path to the script and provide the two parameters, e.g. /home/jtb/code/bringToFront firefox Firefox.

5. From the panel on the left, select global_keybindings, the next folder up. Find the run entry matching the command you just defined, probably run_command_1. Double click it and type the keyboard shortcut you want to use. Put the modifiers in angle brackets, e.g. <Ctrl><Alt>F.

Now Control + Alt + F will bring your firefox window to the front, or launch it if it's not already running.

Here's another way to do it with xdotools. The process to pop-up is recognized by the command line issued to run it (no pid file or unique window title needed).

#!/bin/bash

cmd="$@"
# command line to be run. Note that the resulting
# process will hold this in /proc/PID/cmdline 

pid=`pgrep -nf "^$cmd$"`
# most recent process having "$cmd" in /proc/PID/cmdline

if [ -z "$pid" ]; then # no pid
    exec $cmd
    # run command
else
    winid=`xdotool search --all --pid $pid --onlyvisible | head -1`
    # first visible window owned by pid
    xdotool windowactivate $winid
    # give window focus
fi