shell 常用语法

if语句:
if [ "22" -lt "33" ]
then
 echo "22 less than 33"
else
 echo "no"
fi

case语句:
echo "enter a number"
read ans
case $ans in
1)
echo  "you numer is $ans"
;;
2)
echo "you number is 2"
;;
[3-9])
echo "you number is $ans"
;;
*)
echo "You are input not a sinle number!"
esac

while语句:
i=1
while [ $i -lt 10 ]
do
 echo $i >> newfile
 let i=i+2
done

for语句:
for server in `cat /etc/hosts`
do
 echo  $server
done

for((i=0; i<10; i++))
do
 echo $i
done