Re: More fun with IFS

[Chris F.A. Johnson]

On Wed, 30 Jan 2013, Dan Douglas wrote:

> Hi everyone, and welcome to another edition of IBOTD (IFS-bug-of-the-day),
> featuring everyone's favorite Bourne shell kludge: word-splitting!
>
> On today's episode - inconsistencies within assignments that depend upon
> quoting. Though I can't take credit for discovering this -- it was pointed out
> to me by some guys on IRC after demonstrating some other stuff.
>
> And a quick test:
>
> function expassign {
>         typeset -a a
>         a=("$@")
>         typeset var asn
>
>         while IFS= read -r asn; do
>                 IFS=: command eval "$asn"
>                 printf '%-14s... %s\n' "$asn" "$var"
>         done <<\EOF
> var=${a[*]}
> var="${a[*]}"
> var=$*
> var="$*"
> var=${a[@]}
> var="${a[@]}"
> var=$@
> var="$@"
> EOF
> }
>
> ${ZSH_VERSION+:} false && emulate ksh
> expassign one:::two three:::four
>
> Bash output:                              # I think...
> var=${a[*]}   ... one   two three   four  # bad

   Looks good to me. It expands to multiple words, just as an unquoted
   $* would do.

> var="${a[*]}" ... one:::two:three:::four  # good
> var=$*        ... one:::two:three:::four  # good
> var="$*"      ... one:::two:three:::four  # good
> var=${a[@]}   ... one   two three   four  # bad

   As above.

> var="${a[@]}" ... one:::two three:::four  # good
> var=$@        ... one   two three   four  # bad

   Ditto.

> var="$@"      ... one:::two three:::four  # good
>
> Zsh and pdkshes produce:
>
> one:::two:three:::four
>
> For all of the above, which I think is wrong for the last 4. ksh93 produces:
>
> one:::two three:::four
>
> for the last 4, which I think is correct.

--
   Chris F.A. Johnson, <http://cfajohnson.com/>
   Author:
   Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)
   Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)