Bash while loop that reads file line by line
#!/bin/bash

while read line
do
    echo-e "$ line  n"
done <file.txt

#!/bin/bash
exec 3<file.txt

while read line
do
    echo-e "$ line  n"
done

exec <file.txt

exec 3<file.txt

while read -u3 line
do
    echo -e "$line n"
done

#!/bin/bash
exec 3<file.txt

while read line
do
    echo -e "$line n"
done <&3