What does /dev/null mean in a shell script?

Posted by rishiag on Ask Ubuntu See other posts from Ask Ubuntu or by rishiag
Published on 2014-08-22T17:18:25Z Indexed on 2014/08/23 16:33 UTC
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command-line

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bash

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filesystem

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shell-scripting

I've started learning bash scripting by using this guide: http://www.tldp.org/LDP/abs/abs-guide.pdf

However I got stuck at the first script:

cd /var/log
cat /dev/null > messages
cat /dev/null > wtmp
echo "Log files cleaned up."

What do lines 2 and 3 do in Ubuntu (I understand cat)? Is it only for other Linux distributions? After running this script as root, the output I get is Log files cleaned up. But /var/log still contains all the files.

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