SCP exit 0 when using un-initialized variable and fail to copy
Solution 1:
The variable will be expanded by the shell and in this case prepended to /file_20210302.csv. This means that your destination path is just /file_20210302.csv. You are performing this action as root which has write permission to /. The files are being copied and placed in your root directory, no error is occurring so the exit status is 0.
I tested this with
scp [email protected]:/home/user/test_file $uninitialized_var/tmp/test_file
and it worked as expected, placed the file in /tmp and exit status 0.