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Monthly Archives: September 2015

use awk to find missing element of sequential list

Posted on September 18, 2015 by ForDoDone
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Start with a list of a /24 of IP addresses:

# tail list.txt
        10.1.59.248
        10.1.59.249
        10.1.59.251
        10.1.59.252
        10.1.59.254

Find the missing elements from the sequence of last octets:

# awk -F [./] 'BEGIN{i=0}{i++;if(i!=$4){print i;i=$4}}' list.txt
250
253
Posted in Miscellaneous | Tagged awk | Leave a reply

use dig to monitor DNS server for response

Posted on September 10, 2015 by ForDoDone
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while true; do j=`dig < hostname > @W.X.Y.Z +short`; if [ "$j" != "1.2.3.4" ]; then echo nodig |mail 8185551212@vtext.com; break; fi ; sleep 1m; done;

This particular DNS server was only responding intermittently, so it needed some closer watching

Posted in Miscellaneous, One Liners | Tagged dig, while | Leave a reply
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