shell programming

while loop in shell file

while_loop.sh

#!/bin/bash

num=0
while [ $num -le 5 ]
do
	echo "num : ${num}"
	((num++))
done

output

$ ./while_loop.sh 
num : 0
num : 1
num : 2
num : 3
num : 4
num : 5

while loop in single-line

To do this, use the end-of-line delimiter(;).

example

$ num=0; while [ $num -le 5 ]; do echo "num : ${num}"; ((num++)); done

output

$ num=0; while [ $num -le 5 ]; do echo "num : ${num}"; ((num++)); done
num : 0
num : 1
num : 2
num : 3
num : 4
num : 5

infinite while loop

example

$ num=0; while ((1)); do echo "num : ${num}"; ((num++)); sleep 1; done

output

$ num=0; while ((1)); do echo "num : ${num}"; ((num++)); sleep 1; done
num : 0
num : 1
num : 2
num : 3
num : 4
num : 5
...
...