[SOLVED] '&&' vs. '&' with the 'test' command in Bash

Issue

Consider:

gndlp@ubuntu:~$ test -x examples.desktop  && echo $?
gndlp@ubuntu:~$ test -x examples.desktop  & echo $?
[1] 2992
0

Why is Bash acting the way it is in this situation?

Is the test command simply not finishing and thus the echo command isn't processed?

Solution

The meaning of && and & are intrinsically different.

• What is && in Bash? In Bash — and many other programming languages — && means “AND”. And in command execution context like this, it means items to the left as well as right of && should be run in sequence in this case.
• What is & in Bash? And a single & means that the preceding commands — to the immediate left of the & — should simply be run in the background.

So looking at your example:

gndlp@ubuntu:~$ test -x examples.desktop  && echo $?
gndlp@ubuntu:~$ test -x examples.desktop  & echo $?
[1] 2992
0

The first command—as it is structured—actually does not return anything. But second command returns a [1] 2992 in which the 2992 refers to the process ID (PID) that is running in the background and the 0 is the output of the first command.

Since the second command is just running test -x examples.desktop in the background it happens quite quickly, so the process ID is spawned and gone pretty immediately.

Answered By - Giacomo1968

Answer Checked By - Terry (WPSolving Volunteer)