Ubuntu – Run in terminal not working

Your problem:

The problem is that echo hello world executes within milliseconds, faster than the terminal window is able to pop up.

This means your script already exits before the terminal is visible and therefore its startup is cancelled and you see nothing.

Solution 1 - modify script and add a delay:

You can add a delay (here: 5 seconds) at the end of your script so that it runs longer and you have time to view the result before the script quits and the terminal window closes itself:

#!/usr/bin/env bash
echo hello world
sleep 5

Solution 2 - modify script and wait for a keypress:

You can also add a read command to the end of your script to wait for keyboard input before the script exits.

The -s parameter causes silent input i.e. your pressed key will not be echoed to the terminal.
-n1 lets it read only one single character and returns immediately afterwards instead of waiting for Enter to be pressed.
The -p "Press any key to exit..." argument actually specifies the text to print before waiting for input.

#!/usr/bin/env bash
echo hello world
read -s -n1 -p "Press any key to exit..."

Solution 3 - change gnome-terminal's preference to keep the window open:

Launch a gnome-terminal window, open the Edit menu and select Profile preferences. Navigate to the Commands tab. You will see a drop-down menu labelled When command exits:

Pick Hold terminal open here and close the settings window.

From now on when you double-click on a script and select to run it in a terminal, the window will no longer close itself but stay open and display a banner informing you about the script's exit status:

Warning!
This setting also applies if you manually open a terminal window and try to close it by exiting Bash using the exit command or Ctrl+D - I find it pretty annoying that the terminal window does not close any more then as well.