WHILE loop stops processing after first line of input

I had the below input file and a script whose logic was to process each line of the input file. Within the logic, I needed to perform an OS command such as the “more /etc/oratab” command below.

Contents on the input file:

[server_name] more temp.txt
a
b
c

Code

#! /bin/bash
function perform_logic
{
  echo '***'
  temp=`more /etc/oratab | grep -i dean | wc -l`
}
  
while IFS=',' read -r service lsnr port
do
   echo $service $lsnr $port 
   perform_logic
done < temp.txt

I was expecting three lines of output; one for each line in the input file. However, the output was:

[server_name] ./temp.ksh
a
***
[server_name] 

Basically processing stops after the first line of the input file. The issue is that the “more /etc/oratab” is overlaying the standard input/output of the while command. After I changed the code to:

#! /bin/bash
function perform_logic
{
  echo '***'
  temp=`more /etc/oratab | grep -i dean | wc -l`
}
  
while IFS=',' read -r –u3 service lsnr port
do
   echo $service $lsnr $port 
   perform_logic
done 3< temp.txt 

Now the output displays that all lines of the input file are processed:

[server_name] ./temp.ksh
a
***
b
***
c
***
[dt2ompd2-splunk2]

#! /bin/bash
clear

function perform_logic
{
  echo '***'
  temp=`more /etc/oratab | grep -i dean | wc -l`
}
  
while IFS=',' read -r -u3 service lsnr port
#while IFS=',' read -r service lsnr port
do
   echo $service $lsnr $port 
   perform_logic
done 3< temp.txt 
#done < temp.txt

[dt2ompd2-splunk2] ./temp.ksh
a
***
[server_name]