Don't worry! It's only stuff...

# endless loop
while true
do
  YOUR_COMMAND
done
 
# read from standard input
IN=$(cat /dev/stdin); echo $IN
 
# create sequence
echo $(seq 1 4)
 
# process specified files in directory
for i in *.$1
do
	 echo "$i" "${i%$1}$2"
done
 
# ping all clients
NET=192.168.1
for i in {1..254}; do
   ping  -w 1 -c 1 ${NET}.$i > /dev/null
 
   if [ $? -eq 0 ]; then
      echo ${NET}.$i
   fi
done
 
 
# LINKS
http://www.linuxtutorialblog.com/post/tutorial-conditions-in-bash-scripting-if-statements