Hello experts,

I have a series issue in script that result with bad peformence and I wonder if you can assist me.

For example
I have two files:

File-New, size 15Mb.
File-Old, size 1Mb.

File-New content:
a
b
c
d
File-Old content:
d
f
a
b
c
Result fiel should be:
!a
!b
!c
!d
-f

The current script comapre the lines between these two files in a special order and it takes so long.

The script that currently runs, do the following:
#!/bin/sh
#Input:
# $1 means File-Old
# $2 means File-New
#! - MarkForChange
#- MarkForDeletetion
while read line
do
grep -Fi "$line" $2 >/dev/null 2>&1
if [ "$?" -eq "0" ]; then
echo "! $line"
else
echo "- $line"
fi
done < $1


Do you have any idea how to improve the process.(It take more then hour to run...:-(

Thanks,
Roy.