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Useful Terminal Commands.
#6
(09-26-2018, 04:34 PM)LIFE.LinuxIsForEveryone Wrote: Whenever I install updates, or need to run multiple commands (FYI this is not needed for multiple program installs in-line), I use "&&" in between the commands. 

EXAMPLE: sudo apt update && sudo apt dist-upgrade -yy
--- This isn't needed for programs, as a user can simply space the programs out:$ sudo apt install inxi htop 
Cheers!

I want to expand on that because this little trick is extremely useful but can also cause some headache.

Imagine you have the folloing:
Code:
command1 && command2

command2 will only be executed if command1 ran succesful, i.e. has an exit value of 0.
If command1 encounters an error (has an exit value above 0), command2 will not be run.

you can simulate that with the folloing:
Code:
false && echo "foo"

Now comes the interesting part: You can use || instead of && to run command2 only when command1 fails:
Code:
false || echo "foo"    # "foo" will be displayed
true || echo "foo"    # "foo" will not be displayed

You can also combine both into a one-line if-else-statement
Code:
command1 && command2 || command3

If command1 is succesful, command2 will be executed, if command1 was not succesful, command3 will be executed.

Code:
true && echo "foo" || echo "bar"    # "foo" will be displayed
false && echo "foo" || echo "bar"    # "bar" will be displayed


If you want to run multiple commands and don't want the entire thing to stop when one command encounters an error, use ';':
Code:
echo "foo"; echo "bar"
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Messages In This Thread
Useful Terminal Commands. - by bob777 - 09-02-2018, 02:13 AM
RE: Useful Terminal Commands. - by Cthulhu - 09-02-2018, 02:26 AM
RE: Useful Terminal Commands. - by leon.p - 09-02-2018, 01:56 PM
RE: Useful Terminal Commands. - by bescott9944 - 09-07-2018, 12:27 AM
RE: Useful Terminal Commands. - by leon.p - 09-26-2018, 07:31 PM
RE: Useful Terminal Commands. - by bescott9944 - 06-07-2019, 05:12 AM
RE: Useful Terminal Commands. - by inraidius - 09-27-2018, 02:29 PM
RE: Useful Terminal Commands. - by SirGuyCarleton - 09-27-2018, 11:23 PM
RE: Useful Terminal Commands. - by rick forges - 09-28-2018, 10:01 PM
RE: Useful Terminal Commands. - by leon.p - 10-01-2018, 01:22 PM
RE: Useful Terminal Commands. - by waterismygod - 02-04-2019, 02:02 PM
RE: Useful Terminal Commands. - by Cthulhu - 03-23-2019, 09:47 AM
RE: Useful Terminal Commands. - by leon.p - 03-25-2019, 06:59 PM
RE: Useful Terminal Commands. - by smartin - 07-03-2019, 10:20 AM

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