[Shell Script](EN) Use file or command output in while loop

Process file or result of command in while loop line by line in shell script.

Environment and Prerequisite

• Linux base system
• Bash shell(/bin/bash)

Method Examples

Process command result line by line in while loop

• Use Pipeline

ls ./Test | while read line
do
	echo $line
done

ls /tmp | while read line
do
	echo $line
done

Process file line by line in while loop

• Use Redirection

while read line
do
    echo $line
done < test.txt

• Use Pipeline

cat test.txt | while read line
do
    echo $line
done

Reference

• https://stackoverflow.com/questions/2983213/input-of-while-loop-to-come-from-output-of-command
• https://stackoverflow.com/questions/6980090/how-to-read-from-a-file-or-stdin-in-bash
• Redirect와 Pipe의 차이