UNIX for Dummies Questions & Answers

Hello!
I want to read a file line by line and have each line in a variable. I have found the following code.

Code:

#!/bin/bash
exec 3< data
while read <&3
do echo "The number is $REPLY"
a.out "$REPLY"
done
exec 3>&-

I don't understand the use of exec and its arguments, though having read some man pages and other forums. Could someone please enlighten me?
An example along with the explanation would be welcomed.

It opens file descriptor 3 to read from the file. This seems rather superfluous, as the same can be done by reading straight from the file. The final exec closes the file descriptor again after the loop is finished.

You seem to be missing the variable name on the "read".

Code:

while read REPLY
do
  echo "The number is $REPLY"
  a.out "$REPLY"
done <data

File descriptors are useful as such, and if this was originally part of a bigger program where different files were accessed at different times, it might have made sense originally.

I want to read a file line by line, so I have used the following code:

Code:

exec 3< /tmp/_temp
while read <&3
do
    ....<some operations here for each line which is in the variable RELPY>
# end of loop
done

How can I improve it?

I would do:

Code:

exec < /tmp/file
while read line ; do
       # some stuff involving the variable $line
done