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Parameter expansion resulting empty treated as if it's not empty

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  Parameter expansion resulting empty treated as if it's not empty Oğuz <oguzismailuysal@gmail.com> - 2019-10-30 14:12 +0300

#15538 — Parameter expansion resulting empty treated as if it's not empty

Since

bash -c '${1##*""}' _ foo

prints an empty line, I was expecting

bash -c '${1##*"${1##*}"}' _ foo

to print an empty line too, but instead it prints foo.

Other shells I could find don't have this problem

$ sh -c 'echo "${1##*"${1##*}"}"' _ bar

$ ash -c 'echo "${1##*"${1##*}"}"' _ bar

$ dash -c 'echo "${1##*"${1##*}"}"' _ bar

$ ksh -c 'echo "${1##*"${1##*}"}"' _ bar

$ yash -c 'echo "${1##*"${1##*}"}"' _ bar

$ zsh -c 'echo "${1##*"${1##*}"}"' _ bar

$ bash -c 'echo "${1##*"${1##*}"}"' _ bar
bar
$ bash --posix -c 'echo "${1##*"${1##*}"}"' _ bar
bar

Is this a bug?

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