I have seen lots of uses of single and double-quotes in bash, as well as backtick-quotes, but have never seen what follows. What is the meaning of the transcript below, which seems to show that triple-single-quoting is recognized as meaningful by bash and further seems to show that single quotes inside this thing also have special meaning, enabling interpolation? I have found no documentation of this.
$ Q=test $ echo '$Q' # <== I know, this doesn't work... $Q # <== ...and so it doesn't. $ echo '''$Q''' # <== Don't know what this could mean. $Q # <== OK, nothing special? $ echo ''' "$Q" ''' # <== Try a double-quote?? "$Q" # <== Hmm... OK, nothing. $ echo ''' '$Q' ''' # <== Try a single-quote? test # <== Wow, it did interpolate!? $ echo ''' > ''' # <== Continuation! Proving bash # thinks this is an opening # quote of some kind. $ bash --version # <== FYI, version info GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18) Copyright (C) 2007 Free Software Foundation, Inc.