useful shell commands

commands.sh

# tcpdump ldap traffic to a file, then can be analyzed by wireshark
sudo tcpdump -vv -w /tmp/ldapdump -i lo port 389

#sniff http traffic
sudo ngrep -q -d eth0 -W byline host example.com and port 8180

#Search recursively to find a word or phrase in certain file types, such as C code
find . -name "*.[ch]" -exec grep -i -H "search pharse" {} \; | column -t -s ":"

#search empty folder
find . -empty -type d
du | grep "^0\\s"
find . -not -empty -type d

#bind privileged port (<1024)
sudo apt-get install libcap2-bin  #ubuntu server version needs it
#node listen on lower port ( < 1024 ) , see ref : 
sudo setcap 'cap_net_bind_service=+ep' `which node`
#http://stackoverflow.com/questions/413807/is-there-a-way-for-non-root-processes-to-bind-to-privileged-ports-1024-on-l

#monitor io 
sudo iotop

#monitor CPU
sudo top

#indent selected lines with 2 spaces in VI
:set shiftwidth=2
<v> , select , <>>

#kill process tree (NEGATIVE process number):
kill -TERM -1999


#default ssh remote user other than current user, http://stackoverflow.com/a/10722567/448081
echo "Host xx.com\nUser xjai" > ~/.ssh/config


# download all videos in course 'Machine Learing'
curl https://class.coursera.org/ml-003/lecture/index | grep mp4 | sort | uniq | awk -F\" '{print $4}' | xargs curl -J -L --remote-name 
# -L means follow redirects , --socks5 uses socks5 proxy , --remote-name save file using remote file name from header 'Deposition'