Lesson 9

Date: 3/26/2014
Linux shell scripting tutorial
Linux for Engineering and IT Applications


Looping with while and until statements

  • Script scr2.sh 
    #!/bin/bash
N=1
while [ "$N" -le "10" ]
do
        echo "Number $N"
        N=$[N+1]
done


  • Script scr3.sh 
    #!/bin/bash
N=1 
until [ "$N" -gt "10" ]
do 
echo "Number $N"; N=$[N+1] 
done


    Note, common mistakes in shell scripting are usually due to incorrect syntax. For example, there should be no spaces before and after operator "=" 
    N=1          # correct
N =1         # error
N= 1         # error
N=$[N+1]     # correct
N =$[N+1]    # error
N= $[N+1]    # error


    • Take me to the Course Website