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GwynethLlewelyn/retrieve-list-of-ASN.md

Last active May 31, 2026 23:09
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Retrieve list of AS numbers via whois from Nginx web logs
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retrieve-list-of-ASN.md

This assumes ugrep is installed. ugrep may not be the absolutely fastest grep replacement out there, but it has a substantially faster regular expression engine (invented by Genivia) than most alternatives which usually rely upon Boost (which is fast already!).

It also assumes that whois is installed and listed in $PATH. Adapt as appropriate.

The final sort | uniq may be replaced with sort --unique (if that option is available) and should improve things a little.

LOGFILE=/var/path/something
ug -e '(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' -P --format="%1%~" $LOGFILE | uniq | while read -r line; do whois -H $line | ug -e '(AS\d{1,6})' -P --format="%1%~"; done | sort | uniq
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