One liners

I love one liners, here is a list of a few useful one line scripts


Get all the lines which are not common to the two files.

diff file1 file2 | sed '/^[0-9][0-9]*/d; s/^. //; /^---$/d' > file3

Rename multiple files:
(this removes the extension of all .conf files in current dir)

mmv '*.conf' '#1'

Search and Replace in Multiple Files in perl(easy as PIE)

perl -p -i -e 's/<oldword>/<newword>/g' *

Remove comments and blank lines from file

egrep -v '^$|^\s*#' configfile

Find out which process is using up your memory using ps, awk, sort

ps aux | awk '{if ($5 != 0 ) print $2,$5,$6,$11}' | sort -k2n

ps ­eo user,pid,pcpu,cmd,args ­­sort ­pcpu | head ­n20

Find out Top 10 Largest File or Directory Using du, sort and head

du -sk /var/log/* | sort -r -n | head -10

Find out Top 10 Most Used Commands.

cat ~/.bash_history | tr "\|\;" "\n" | sed -e "s/^ //g" | cut -d " " -f 1 | sort | uniq -c | sort -n | tail -n 15

Search mail logs for log in attempts

for i in `ls /var/spool/mail`; do echo $i; cat /var/log/maillog* | grep -i LOGIN| grep $i | wc -l; done

for i in `ls /var/spool/mail`; do echo $i; cat /var/log/maillog* | grep -i LOGIN| grep "authid="$i | wc -­l; done

Check Top Connections

PORT=110;netstat ­antp | awk '$4 ~ /:'$PORT'$/ {c++;print $5|"cut ­f1 ­d:|sort |uniq ­c| sort ­n"} END {print c}