Until loop 

The until loop is very similar to the while loop, except that the loop executes until the TEST-COMMAND executes successfully. As long as this command fails, the loop continues. The syntax is the same as for the while loop:

until TEST-COMMAND; do CONSEQUENT-COMMANDS; done

The return status is the exit status of the last command executed in the CONSEQUENT-COMMANDS list, or zero if none was executed.TEST-COMMAND can, again, be any command that can exit with a success or failure status, and CONSEQUENT-COMMANDS can be any UNIX command, script or shell construct.

Example :--            Write a shell script to display first ten positive numbers using until loop.         

                          

Program

num=1

until [ $num –gt 10 ]; do

echo num

num=`expr $num + 1 `

done

OUTPUT:

1

2

3

4

5

6

7

8

9

10