Execute command in terminal an don't wait its return

Solution 1:

Use

firefox &

It will create firefox process in background and you can work in terminal

Solution 2:

Firefox 35 on Ubuntu 14.04 detaches itself from the shell, still printing errors though, to eliminate that output, try:

firefox >/dev/null 2>&1 www.google.com &

The
>/dev/null makes firefox's 'stdout' text stream be sent to "nowhere",
2>&1 makes 'stderr' be sent to the same place,
& detaches firefox from the shell.

With Bash "job control" of a long running process, e.g. find on / as in:

find -printf "%p\n" / >$HOME/LIST-OF-FILES.txt

... at any time before it finishes, you can do this:
Hold Ctrl and hit Z

[1]+  Stopped                 find ...

will be printed and the shell prompt will reappear...
type bg and press enter to have find continue run in the background.
Note that errors and warnings will still be printed, as in...

find: /run/lightdm: Permission denied

To stop those from appearing, add 2>/dev/null to the command line.

Another alternative to launch GUI based software is

xdg-open firefox ...

... this is more equal to actually clicking on an icon in your OS.

NOTE: Ubuntu. There are various variants of this for other Linux-variants, and MacOS.

Look up "job control" in http://www.tldp.org/LDP/abs/html/abs-guide.html - for more info.

Solution 3:

Ctrl+Z is what you're looking for and then afterwards type bg Enter

Alternatively (but you'll take a bit of getting used to it) is typing firefox& instead of firefoxCtrl+Z bg Enter