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Thanks! I have tried using bash substitution to solve it but failed (I just learned the difference between "#" and "##").

FYI, these substitutions are POSIX:

Also a couple mnemonic hints:

% vs #. On US keyboards, # is shift-3 and is to the left of % which is shift-5. So # matches on the start (left) and % matches on the end (right).

# vs ## (or % vs %%). Doubling the character makes the match greedy. It's twice a wide so it needs to eat more.

Bash also supports ${parameter/pattern/string} and ${parameter//pattern/string} (and a bunch others besides) which are not POSIX:

Thanks for the great information!