But if all I need to do is generate the report I proposed...why would I embed that in a Ruby script (or a Python script, or a Perl script, etc.) when I could just use a bash script?
Bash scripts tend to grow to check on file presence, conditionally run commands based on the results of other commands, or loop through arrays. When it is a nice pipelined command, yes, bash is simpler, but once the script grows to have conditions, loops, and non-string data types, bash drifts into unreadability.
But if all I need to do is generate the report I proposed...why would I embed that in a Ruby script (or a Python script, or a Perl script, etc.) when I could just use a bash script?