shell while if ...

#!/bin/bash
n=1
while (( $n <= 5 ))
do
 echo "Welcome $n times."
 n=$(( n+1 )) 
done

add： https://bash.cyberciti.biz/guide/While_loop

#!/bin/bash
read -p "Enter number : " n
if test $n -ge 0
then
 echo "$n is positive number."
else
 echo "$n number is negative number."
fi
add:https://bash.cyberciti.biz/guide/If..else..fi