The script that I used ran fine for various flavors of Linux for a long time. But somehow, it produced unwanted dollar sign on Ubuntu 18.04, so my hours of troubleshooting starts.

The simplest one I can say is I use echo with tab and variables and piped that to awk through AWS Systems Manager. It is similar to the following:

v='variable'
TAB=$'\t'
echo "${v}${TAB}" | awk '{print $0}'

In many flavors of Linux other than Ubuntu 18.04, even in Ubuntu 16.04, it produced the expected result:

variable

However, in Ubuntu 18.04, it ends the result with an extra dollar sign:

variable$

At first, I thought it marks end of line or the typical \0 (NUL character) that marks end of string, so I tried various ways to remove it such as using tr, gsub, etc. But none of them works.

Eventually, I found out that the dollar sign comes from the TAB variable. To solve it, I have to replace the above with:

echo -e "${v}\t"