always true while loop

JDska55 · 08-17-2009, 03:45 PM

Hey guys-
Here's a real easy one for you. I need to make a while loop in bash that's always true. I will manually break out of it later on in the script. I thought one of these would work, but the script never enters the loop for some reason:

Code:

while:

while (1)

while [1]

Thoughts?

Jarrod

Tinkster · 08-17-2009, 03:50 PM

So what's the body of your loop?

Code:

while true; do   date;   sleep 5; done                                                                                        
Tue Aug 18 08:49:35 UTC 2009
Tue Aug 18 08:49:40 UTC 2009
^C

Cheers,
Tink

i92guboj · 08-17-2009, 04:40 PM

In bash there's a command called ":", which is always evaluated to true, you could use that to shorten it even more (however I advice to use "true" if you are writing this into a script if only for the sake of readability).

Code:

$ while :; do echo foo; sleep 5; done
foo
foo

You could also use any other command that you are sure will end without error (true). In this case you could use this, for example:

Code:

$ while sleep 5; do echo foo; done

Whose effect will be slightly different, I bet you can guess what the difference is