By using the & symbol you can execute a second command after the first command.
as an example, let’s try the following from command prompt.
echo hello
which outputs hello of course
now let’s try the same again but with the addition of &
echo hello & echo goodbye
This now outputs hello, and then outputs goodbye as well
You can achieve the same result but with the caveat that the second command should only run if the first command was successful, this could be extremely important for lots of reasons and could alter the whole dynamic of your script.
Lets use ping to show this example
ping localhost & echo Yes, ping got a reply!
This pings localhost which should always be available and then outputs our text
Now to try with &&
ping localhost && echo Yes, ping got a reply!
This does the same
So let’s try to ping an address that is not reachable and check the results
ping 0.0.0.0 & echo Yes, ping got a reply!
This runs ping which fails but goes ahead and runs our second command regardless, although it has done what we have instructed the visible results are not really accurate and could affect our script / results.
Now let’s try it again using &&
ping localhost && echo Yes, ping got a reply!
This time ping is run but as it is not successful the second command is not executed.
This brings us on the third condition || this only executes text if the command was unsuccessful
So, let’s try this
ping localhost || echo No, ping did not get a reply!
Ping runs successfully and therefore does not execute the second command
And again but this time to an address that will fail
ping 0.0.0.0 || echo No, ping did not get a reply!
as expected, ping is unsuccessful so the second command gets executed
Now, lets put && and || together to cover both eventualities!
ping localhost && echo Yes, ping got a reply! || echo No, ping did not get a reply!
Ping executes successfully and then runs the second command, the third option || is not executed
Now, lets ping the address we now will fail
ping 0.0.0.0 && echo Yes, ping got a reply! || echo No, ping did not get a reply!
This time ping has returned unsuccessful so the second command && is not executed but the third command || is
