Bash scripting || sed command - bash

Question

I am trying to add # in front of a line if string gets a match.
String will be read by user.
Direct sed command well for me but when is user read command then it throws error:
server cust01-stg01-ins01-wfm13-bck-610358970-22.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-25.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-21.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-23.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-24.int.stg.mykronos.com:80 resolve max_fails=0;
Now suppose user want to comment line with matching character "cust01-stg01-ins01-wfm13-bck-610358970-22" then below output is expected
#server cust01-stg01-ins01-wfm13-bck-610358970-22.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-25.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-21.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-23.int.stg.mykronos.com:80 resolve max_fails=0;
server cust01-stg01-ins01-wfm13-bck-610358970-24.int.stg.mykronos.com:80 resolve max_fails=0;
sudo sed -i "/cust01-stg01-ins01-wfm13-bck-610358970-23/s/^/#/" wfm_backend_nginx.state
this works well for me but when I am trying below command then it is throwing error.
[root#cust01-stg01-ins01-wfm13-bck-ilb1-610358970 tmp]# cat ilb_commnet.sh
#!/bin/bash -xe
sudo read -p "enter host_name :" Host
sudo sed -i -e "/${Host}/s/^/#/" /tmp/wfm_backend_nginx.state
Output is :
sed: -e expression #1, char 0: no previous regular expression

Answer 1

sudo read -p "enter host_name :" Host
sudo runs a separate process, that will read the input and save it into Host. Then the process will exit, destroying the whole environment with the read value.
Remove sudo - read the value in current process.

Answer 2

Using sudo is completely crazy here. You are running read in a privileged subshell, which then exits and takes the variable with it before you can use it for anything.
... Actually sudo read is simply a syntax error because sudo can't run a shell built-in. It tries to look for /usr/bin/read, /bin/read etc but doesn't find anything.
bash$ sudo read -p hello
sudo: read: command not found
Even without the sudo, your code should probably examine the variable before attempting to pass it to a privileged command. Maybe something like
#!/bin/bash -xe
while true; do
read -p "Enter host name: " Host
case $Host in
*[!A-Za-z0-9]*) echo "$0: Invalid characters in host name" >&2;;
*) break
esac
done
sudo sed -i -e "/${Host}/s/^/#/" /tmp/wfm_backend_nginx.state