1. The script requires 3 filenames as arguments, e.g., ./script1 file1 file2 file3. Which files are input files and which are output files?

2. Inside the while-loop, why does variable $line have to be enclosed by double quotes?

$cat script1

#!/bin/bash

exec 3<$1

exec 4<$2

exec 5>$3

while read line <&3

do

echo $line >&5

done

while read line <&4

do

echo $line >&5

done