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An Introduction to Shell One Liners

The knowledge and use of the command line is a powerful tool that can aid in the creation, modification and automation of routine tasks that a security auditor or any computer user may come up against.  The flexibility, simplicity, and leetness of the shell oneliner can replace thousand-line perl code which otherwise would be thrown away after the task is complete.  We have decided to provide share some of our favorite oneliners that we have found useful, either culled from other sources or created by ourselves.  All of these examples should run comfortably from a Linux bash shell or Cygwin-Windows equivalent, with the required applications listed in the oneliner.

The topic of this week is IP address manipulation:

# Sort by IP Addresses
sort -n -t. -k1,1 -k2,2 -k3,3 -k4,4

# Sort by IP Addresses and Port like IP:PORT
sed 's#:#.#' | sort -n -t. -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 | sed 's#(([0-9]{1,3}.){4})#1:#;s#.:#:#'

# IP2HOST: IP -> IP (HOST) using 'bind-host' package built into Ubuntu
for i in $(cat ips.txt); do echo "$i ("`host $i | grep -v NXDOMAIN | cut -d' ' -f5`")"; done | sort -n -t. -k1,1 -k2,2 -k3,3 -k4,4 | sed 's#()##' | tee ip_hosts.txt

# HOST2IP: HOST -> IP (HOST) using 'host' package available in Ubuntu
for i in $(cat hosts.txt); do host `echo "$i" | tr -d [[:blank:]]` | grep -v -e 'alias' -e 'handled' -e 'timed' | sed 's/Host (.*) .*/1 0.0.0.0/' | sed "s/;;.*/$i - - 0.0.0.0/" | awk -F' ' '{printf "%s (%s)n",$4,$1}'; done | sort -n -t. -k1,1 -k2,2 -k3,3 -k4,4 | tee ip_hosts.txt

#Print IP addresses in a file
egrep -o '[[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}'

# Print IP addresses in a file: Perl edition
perl -nle 'print $& if /(d{1,3}.){3}d{1,3}/'

# Print IP address in all files in the current directory tree with some pretty color matching
find . -type f -exec egrep -a -H -n --color=auto '[[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}' {} ;

Thanks to readers for suggesting the color syntax support implemented using wp-syntax. I furthermore learned that the Visual Editor of WP was oppressing my HTML code, stripping tags in the WP-Syntax <pre> tag that should be present, so I’ll be keeping my edits in HTML mode from now on.

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