Replace variable in bash file using sed - output lags - linux

Question

I'm trying to write a bash script that search and replace a specific
user input saved in config.sh using sed. This does work; however it
only works partially as shown below.
config.sh
#!/bin/bash
#
#UserName to be deleted
delUserName=""
#Source
delUserSrc=/Users/"$delUserName"
#Destination
delUserDest=/Users/John/BackUp/"$delUserName"/"$delUserName".zip
main.sh
#!/bin/bash
#
source scripts/config.sh
echo -e "\nEnter user you wish to delete: \c"
read -r UserName
sed -i '' -e "s/delUserName=.*/delUserName=$UserName/g" scripts/config.sh
echo -e "delUserName: $delUserName"
echo -e "delUserSrc: $delUserSrc"
echo -e "delUserDest: $delUserDest"
output1:
Enter user you wish to delete: Test
delUserName:
delUserSrc:/Users/
delUserDest:/Users/John/BackUp/ / .zip
output2:
Enter user you wish to delete: Test1
delUserName:Test
delUserSrc:/Users/Test
delUserDest:/Users/John/BackUp/Test/Test.zip
output3:
Enter user you wish to delete: Test1
delUserName:Test1
delUserSrc:/Users/Test1
delUserDest:/Users/John/BackUp/Test1/Test1.zip
expected output1:
Enter user you wish to delete: Test
delUserName:Test
delUserSrc:/Users/Test
delUserDest:/Users/John/BackUp/Test/Test.zip
expected output2:
Enter user you wish to delete: Test1
delUserName:Test1
delUserSrc:/Users/Test1
delUserDest:/Users/John/BackUp/Test1/Test1.zip
The script lags. sed instantaneously changed the value for $delUserName BUT The proper values for $delUserName, $delUserSrc, and $delUserDest only echo on the 2nd run. The scripts run well when all variables are in main.sh except i have to do it this way. Save the user input into $UserName. Any idea why the values don't show when run the 1st time?
Thanks

Answer 1

Here is what I think is happening.
The sed command replaces text in files. It does not modify the value of variables in memory. These values are assigned when you source config.sh.
So right after your sed line, you need to put this line :
source scripts/config.sh
It is the same line as above in your script. This is required there also so that your newly replaced values will be loaded in the variables so that you can display them. Once the new values are loaded in memory, then the echo statements will be able to expand the variables to that new value.