How to use while loop in the shell script
How to use while loop in the shell script
In this article, we will see how to use while loop in the shell script.The while loop enables you to execute a set of commands repeatedly until some condition occurs. It is usually used when you need to manipulate the value of a variable repeatedly.
Syntax:
while command
do
Statement(s) to be executed if command is true
done
Here the Shell command is evaluated. If the resulting value is true, the given statement(s) are executed. If the command is false then no statement will be executed and the program will jump to the next line after the done statement.
#! /bin/bash
#first while loop (loop are command which is used repeatly while loop). if condition is true then while loops work
while [ condition ]
do
command1
command2
command3
done
Example:
n=1
while [ $n -le 5 ]
do
echo "$n"
(( n++ ))
done
Example:
n=6
while [ $n -le 8 ]
do
if [ $n -le 10 ]
then
echo "condition is true"
else
echo "condtion is false"
fi
echo "$n"
n=$(( n+1 ))
done
#sleep command during while loop to give some second time to go next step
n=1
while [ $n -le 2 ]
do
echo "$n"
(( n++ ))
sleep 1
done
Example:
n=1
while [ $n -le 3 ]
do
echo "$n"
(( n++ ))
done
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