Can I use the same variable name in bash for multiple parallel background processes?

Question

In the shell script below, I would like to run 2 commands parallel in the background to speed up the process, wait for them to finish and continue to run some more commands afterwards.

As I am using the same variable name (DATASERVERNAME) in both loops, are these variables going to interfere with each other in the background? Should I use different variable names, like DATASERVERNAME_SYBASE, DATASERVERNAME_ORACLE in each loop instead?

#!/bin/bash
while read DATASERVERNAME
do
  some commands here
done < sybase_data_servers.txt &

while read DATASERVERNAME
do
  some commands here
done < oracle_data_servers.txt &

wait

some more commands here

Answer 1

Your script is safe as you could reveal through a little experiment:

#!/bin/sh -eu
echo A > a
echo B > b

X=0

while read X
do
  echo X=$X
done < a &
wait

echo X=$X

while read X
do
  echo X=$X
done < b &
wait



echo X=$X

Script output:

X=A
X=0
X=B
X=0

The backgrounded loops run in different processes ($BASHPID should reflect that too).