Find the largest file in a directory tree
find /path -type f -exec ls -s {} \; | sort -n | tail -1
Compress the contents current directory, but compress the smallest files first
ls -s | awk NR!=1 | sort -n | awk ‘{print $2}’ | xargs bzip2 -9v
Using netstat
netstat -ntulp displays everything that is listening tcp and udp and the ip that it is listening on
View network traffic (by port number)
To view web traffic (for example) use tcpdump -s 0 -w – port 80 | tcpdump -r – -A
Filter duplicate lines from a sorted files
cat list-1 list-2 list-3 | sort | uniq > final.list
Debugging bash scripts
Debugg bash scripts by runing with option -x example bash -x scriptname.sh
lowercase filen names
#! /bin/bash DIR=$1 for a in `ls $DIR` do fname=`echo $a | tr A-Z a-z` mv $DIR/$a $DIR/$fname done; exit 0