From: Stephane Chazelas <stephane.chazelas@gmail.com>
To: Zsh hackers list <zsh-workers@zsh.org>
Subject: unset arbitrary associative array element
Date: Sat, 11 Aug 2018 12:22:26 +0100 [thread overview]
Message-ID: <20180811112226.tiscidxlc7edxqmg@chaz.gmail.com> (raw)
Hi,
one can set an arbitrary associative array element with:
typeset -A hash
hash[$key]=$value
But:
unset "hash[$key]"
Doesn't work for values of $key that contain "]" or "\" (or
characters whose encoding contain the bytes 0x5c or 0x5d) or for
an empty $key.
hash[$key]=()
doesn't work ("attempt to set slice of associative array"
error).
unset "hash[${key//(#m)[]\\]/\\$MATCH}]"
addresses keys with "]" and "\" but not those with characters
whose encoding contains 0x5c/5d or the empty key.
Is there any other way, other than recreating the full array
with something like:
hash=("${(@kv)hash[(I)^$key]}") # untested
ksh93 has the same kind of issues (plus various bugs for
characters that contain 0x5c/5d bytes), but supports unset
"hash[]" (even though like zsh it doesn't support hash[]=value).
In bash, one can do:
unset 'hash[$key]'
That is, the argument is evaluated as shell code! That means we
can unset arbitrary elements that way (though note that bash
doesn't support hash elements with empty keys!), but I would not
want to go there for bash as that means that things like
unset "hash[$key]"
are command injection vulnerabilities.
Not sure what's the best way to address it. Maybe like for
typeset and co, make "unset" a keyword where in
unset hash[$key]
That a[$key] is parsed the same way as in
hash[$key]=value
Or maybe a:
unset -k "$key" hash
Or
hash+=("$key") # add element without a value removes the element
In any case, it would be useful if we could set or unset the
element with the empty key with:
hash[]=value
unset "hash[]"
--
Stephane
next reply other threads:[~2018-08-11 11:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-11 11:22 Stephane Chazelas [this message]
2018-08-11 14:55 ` Sebastian Gniazdowski
2018-08-12 3:38 ` Sebastian Gniazdowski
2018-08-12 6:06 ` Stephane Chazelas
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