UNIX for Dummies Questions & Answers

hi,
i want to create a script that will search and replace the values inside a particular file. i have 5 files that i need to change some values inside and i don't want to use vi to edit these files. All the inputted values on the script below will be passed into the files.

cho ""
echo "Domain_name "
read domain_name
echo "Work path Name : "
read wk_path_name
echo "Server Name 1: "
read server1name
echo "Admin Port: 1: "
read adminport1
echo "Server Name 2: "
read servername2

echo "Admin Port: 2: "
read adminport2
echo "Multicast Addr :"
read mcast_addr
echo "Multicast Port :"
read mcast_port

for i in list.txt do
cat $i |sed -e 's/oldpattern/$domain_name/g' $i > $i".new"
done

Problems
1. how to pass the values entered from "read" command thru the "oldpattern"?
2. how to pass the values without creating a new file? is there any way.

For your qn1,
below one will be a solution...

read oldval
read newval
while read line
do
{
sed 's/'$oldval'/'$newval'/g' $line >$line".new"
}
done<list.txt

For your qn2.,
I believe there is no other way other than creating a temp file which contains the output of sed command and then renaming it to the original filename...

For q2, GNU sed has -i option

Script to replace :
[root@unixguy ~]# cat replace.sh
#!/bin/bash
read oldval
read newval
while read line
do
{
sed 's/'$oldval'/'$newval'/g' $line >$line".new"
}
done<list.txt


Script I ran
[root@unixguy ~]# ./replace.sh
home-world
sriram
sed: can't read /home/sriram/test: No such file or directory
./replace.sh: line 3: $line".new": ambiguous redirect
[root@unixguy ~]# cat test
jshsyh hshhshsh kkkshshhshsh kjsjjsjsj ksjsjj js
jshsyh hshhshsh kkkshshhshsh kjsjjsjsj ksjsjj js
home-world hshhshsh kkkshshhshsh kjsjjsjsj ksjsjj js

can u advice where i am going wrong ???