linux shell for loop example syntax

                Linux shell for loop example syntax

Shell Loop :

In this chapter, we will discuss shell loops in Unix. A loop is a powerful programming tool that enables you to execute a set of commands repeatedly. In this chapter, we will examine the following types of loops available to shell programmers - 

Syntax :

while command1;  # this is loop1, the outer loop

do

   Statement(s) to be executed if command1 is true

   while command2 ; # this is loop2, the inner loop

   do

      Statement(s) to be executed if command2 is true

   done

   Statement(s) to be executed if command1 is true

done

Example :

#!/bin/sh

a=0

while [ "$a" -lt 10 ]    # this is loop1

do

   b="$a"

   while [ "$b" -ge 0 ]  # this is loop2

   do

      echo -n "$b "

      b=`expr $b - 1`

   done

   echo

   a=`expr $a + 1`

done

Read-only Variables :

#!/bin/sh

NAME="Zara Ali"

readonly NAME

NAME="Qadiri"