i'm new to Linux,

i'm trying to a simple script like a batch files(ms-dos) and i have no succes and i don't understand why not work.

i.ve read all tutorial on linuxcommand.org

here is my problem

#nothing here
echo "Hello"
Alias cls=clear
echo "world"

echo 1 and 2 work,but alias is not executed ,alias cls=clear work on command line,not in the script.

shell permission on my files is ok

no command "cls" found is the result

i have read tutorial many times

thanks in advance