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From: ZyX <kp-pav@yandex.ru>
To: Ray Andrews <rayandrews@eastlink.ca>,
	"zsh-users@zsh.org" <zsh-users@zsh.org>
In-Reply-To: <562D9E85.7080006@eastlink.ca>
References: <562D31C3.9030705@eastlink.ca>
	 <151025180235.ZM30558@torch.brasslantern.com> <562D9E85.7080006@eastlink.ca>
Subject: Re: greps pipes and eval bad patterns
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Date: Mon, 26 Oct 2015 16:04:07 +0300
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26.10.2015, 06:32, "Ray Andrews" <rayandrews@eastlink.ca>:
> On 10/25/2015 06:02 PM, Bart Schaefer wrote:
>> šOn Oct 25, 12:47pm, Ray Andrews wrote:
>> š}
>> š} test1 ()
>> š} {
>> š} gstring=" | grep \[01;34m "
>> š} tree --du -haC | grep -Ev "^[^\[]{$levels}\[*" "$gstring"
>> š} }
>>
>> šOne doesn't normally build up a pipeline that way, but if you must
>
> What would be the better way? I'm not wedded to anything, just looking
> for the
> appropriate method.
>> šššdo
>> šso, you're on the right track with "eval" -- you just haven't applied
>> šenough quoting. "eval" is going to re-parse everything, so you need
>> što quote everyhing to the same depth:
>>
>> šššššševal 'tree --du -haC | grep -Ev "^[^\[]{$levels}\[*"' "$gstring"
>>
>> šThe single quotes (before tree and after the levels pattern) keep the
>> šfirst pipeline (and importantly the double-quotes that are around the
>> šgrep pattern) from being interpreted until eval does so.
>
> Enlightenment. We freeze all expansions with single quotes until eval
> sorts it all out in
> one go.
>
>> šThe use of
>> šthe parameter for $gstring has the same effect.
>>
>> šYou might be able to see this better if you assign everything to
>> švariables before eval-ing, e.g.
>>
>> šššštest1 ()
>> šššš{
>> šššššššgstring="| grep \[01;34m "
>> šššššššglevels='| grep -Ev "^[^\[]{$levels}\[*"'
>> ššššššštree="tree --du -haC"
>> ššššššševal "$tree" $glevels" "$gstring"
>
> Yeah, that's the sort of thing I'm used to doing I just didn't know how
> to handle the
> tricky characters. It makes nothing but sense now that I see it. So the
> final product
> becomes:
>
> t ()
> {
> šššššlocal gstring=
> ššššš[ "$1" = ',f' ] && { gstring=' | grep "\[01;34m" '; shift }
> šššššinteger levels=$(( ($1 + 1) * 4 ))
> ššššševal ' tree --du -haC | grep -Ev "^[^\[]{$levels}\[*" ' $gstring
> šššššdu -sh .
> }

Specifically this I would write as

    local -a gcmd
    gcmd=( cat )
    if [[ $1 == ,f ]] ; then
        gcmd=( grep '\[01;34m' )
        shift
    endif
    integer levels=$(( ($1 + 1) * 4 ))
    tree --du -haC | grep -Ev '^[^\[]{'"$levels"'\[* ' | $gcmd

>
> ... a better tree than tree.