Re: unmatched '

[Ray Andrews <rayandrews@eastlink.ca>]

On 09/03/18 12:23 PM, Bart Schaefer wrote:
> You really should never do this with "eval". Consider what happens if the
> file name is /etc/Why you should never `rm -rf /`
>
> (Obligatory warning:  DO NOT TRY THAT AT HOME.)
I probably have a lot of improper constructions here, I use the first 
thing that seems to work, and later I repent of various sins as they 
become apparent.  How would I best do that sort of thing?
> Why are you putting stuff like that file in /etc/ in the first place?

Heck, not me!  That's stock Debian, I'd not create a directory like that 
on pain of damnation.  Debian should not allow it either, IMHO.

> If $bar is a file name with spaces in it, 

$bar will start with a list of directories as originally output by 
'find', so whatever my code, it has to handle whatever 'find' might find.
> Based on your description there must be a leading "|" in $grepstring.
> Don't do that.
Yeah:

     ccolor=33      # Start with yellow, then blue, magenta, cyan.
     for file in "$@"; do
         # We colorize the already selected lines here:
         grepstring="$grepstring | GREP_COLOR='01;'"$ccolor" grep $wwild 
$ccase --color=always \"$file\""
         (( ccolor++ )) # Next color.
     done

... so I'm filtering and colorizing however many arguments there are to 
the command, so each iteration must (?) begin with the pipe.  And the 
final string:

     bar=(`eval "find -H -O3  / -warn  -type d -ipath \"*$1*\"" 
$grepstring`)
> Assuming you've carefully sanitized $grepstring to avoid gotchas like
> unintentional `...` or $(...) substitutions, the closest you should
> ever get to what you're doing is
>
> baz=( `print -lr -- "${bar[@]}" | eval "$grepstring"` )
>
> There's probably a better way to do your cascade of greps, too, such
> as building a file with one pattern per line and running a single
> "grep -f patternfile", but you haven't provided sufficient context.
>
The $grepstring itself can't have any surprises (famous last words) but 
the entire construction is of course suspect.  I see you're shrinking 
the target of eval to the minimum, that seems sensible on first 
principals but I can't think of a way to get the first pipe outside of 
$grepstring.  The thing is just to turn a string into a command because 
the only way I know to create flexible commands is by way of strings.

Anyway, is there no way of putting a global protection on nasty 
characters inside the list of directories?  I'm sure I did read about 
that, but there's so much to remember.

BTW I started doing this sort of cascading colorization with a very 
similar function I use to explore the history.  I can refine the search 
with as many strings as I want, and they all show up with different 
colors, which is even useful, not just eye candy. The final array gets 
fed to Sebastian's 'n_list' for selection. Quite indispensable to me.