Question

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

Answer 1

A1.

1. file1, file2, file3 are the command line arguments to script1. Developers can treat any of the arguments as input or output. Please find below snapshots :

.

A. 2

Its not mandatory to use double quotes here.

The reason you double quote variables is because the contents of the variable may include spaces. A space is typically the boundary character which denotes a break in atoms within a string of text for most commands.

Code will work fine without double quote as well :

bash-4.4$ line-Test line" bash-4.4$ flag-1 bash-4.4 while [ $flag -eq 1 ] > do > echo $line > flag-e done Test line

Hope it helps,

Happy Learning