Re: greps pipes and eval bad patterns

[ZyX <kp-pav@xxxxxxxxx>]

26.10.2015, 06:32, "Ray Andrews" <rayandrews@xxxxxxxxxxx>:
> On 10/25/2015 06:02 PM, Bart Schaefer wrote:
>>  On Oct 25, 12:47pm, Ray Andrews wrote:
>>  }
>>  } test1 ()
>>  } {
>>  } gstring=" | grep \[01;34m "
>>  } tree --du -haC | grep -Ev "^[^\[]{$levels}\[*" "$gstring"
>>  } }
>>
>>  One 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.
>>    do
>>  so, you're on the right track with "eval" -- you just haven't applied
>>  enough quoting. "eval" is going to re-parse everything, so you need
>>  to quote everyhing to the same depth:
>>
>>       eval 'tree --du -haC | grep -Ev "^[^\[]{$levels}\[*"' "$gstring"
>>
>>  The single quotes (before tree and after the levels pattern) keep the
>>  first pipeline (and importantly the double-quotes that are around the
>>  grep 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.
>
>>  The use of
>>  the parameter for $gstring has the same effect.
>>
>>  You might be able to see this better if you assign everything to
>>  variables before eval-ing, e.g.
>>
>>     test1 ()
>>     {
>>        gstring="| grep \[01;34m "
>>        glevels='| grep -Ev "^[^\[]{$levels}\[*"'
>>        tree="tree --du -haC"
>>        eval "$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 ()
> {
>      local gstring=
>      [ "$1" = ',f' ] && { gstring=' | grep "\[01;34m" '; shift }
>      integer levels=$(( ($1 + 1) * 4 ))
>      eval ' tree --du -haC | grep -Ev "^[^\[]{$levels}\[*" ' $gstring
>      du -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.