Q:

How to read using "read" from file descriptor 3 in bash script?

http://bash.cyberciti.biz/file-management/shell-script-to-simulate-unix-more-command/
#!/bin/bash
# Write a shell script like a more command. It asks the user name, the
# name of the file on command prompt and displays only the 15 lines of
# the file at a time.
# -------------------------------------------------------------------------
# Copyright (c) 2007 nixCraft project <http://cyberciti.biz/fb/>
# This script is licensed under GNU GPL version 2.0 or above
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------

counter=1
echo -n "Enter a file name : "
read file

if  [ ! -f $file ]
then
    echo "$file not a file!"
    exit 1
fi

# read file line by line
exec 3<&0
while read line
do
       # pause at line no. 15
    if [ $counter -eq 15 ]
    then
        counter=0 # reset counter
        echo " *** Press [Enter] key to continue ..."
        read -u 3 enterKey
    fi
    echo $line
    (( counter++ ))
done < $file

This emulates more command..
I get this error..

read: 26: Illegal option -u

Make sure to enter the name of a file which has more than 15 lines..
Also I read the man page of "read" and i didnt get an option like "-u"..
So, how do i read using "read" from the file descriptor 3 (which is copy of stdin).

A:

try
read key <&3

A:

It's also possible to get bash to assign a file descriptor to a variable;
The next free descriptor number will be allocated starting from 10.
For example:
#!/bin/bash
FILENAME="my_file.txt"
exec {FD}<${FILENAME}     # open file for read, assign descriptor
echo "Opened ${FILENAME} for read using descriptor ${FD}"
while read -u ${FD} LINE
do
    # do something with ${LINE}
    echo ${LINE}
done
exec {FD}<&-    # close file

