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Sender: Scott Moser <ssmoser2@gmail.com>
Date: Wed, 7 Nov 2012 14:13:36 -0500 (EST)
From: Scott Moser <smoser@ubuntu.com>
X-X-Sender: smoser@brickies
To: zsh-workers@zsh.org
Subject: bug in parameter expansion
Message-ID: <alpine.DEB.2.02.1211071358140.4960@brickies>
User-Agent: Alpine 2.02 (DEB 1266 2009-07-14)
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This issue was initially reported against shell code delivered in
cloud-init at [1], but it seems to me to be a bug in zsh's posix shell
behavior.

$ for shell in /bin/dash /bin/bash /bin/ksh /bin/zsh; do \
  echo "=== $shell ==="; $shell -c 'echo "${1%%=*}"' \
  -- A=B; done
=== /bin/dash ===
A
=== /bin/bash ===
A
=== /bin/ksh ===
A
=== /bin/zsh ===
zsh:1: * not found

It also has the issue when matching prefix (#):
$ zsh -c 'echo ${1#=?}' -- =AB
zsh:1: ? not found
$ bash -c 'echo ${1#=?}' -- =AB
B

It is seemingly easily worked around by escaping the '=' like:
  $ zsh -c 'echo "${1%%\=*}"' -- A=B
  A
or:
  zsh -c 'equal="="; echo "${1%%${equal}*}"' -- A=B
  A

Scott
--
[1] https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1073077