Re: multios stripping colors?

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

On 31/01/18 11:30 PM, Oliver Kiddle wrote:
> Ray Andrews wrote:
> >       $   eval "$@"
> >
> > That line in a function of mine can successfully eat some very complex
> > input including various pipes and color codes.  However, when I try this:
> eval "eats" only shell syntax. Colour codes are eaten by your
> terminal. Perhaps you contrived to prevent them being generated or
> constructed something to filter them out.
Of course.  Here's a current example:

            _execute aptitude search \'$iinst ?description($1)\' '|' 
egrep --color \'^\|$1\ $ggrep_oneline\'

'_execute' is a function that contains the above 'eval' plus a few other 
things.  As I run it with the line just above, I get 'aptitude' output 
colored via egrep ....
> > $ eval "$@" >&2 >! /tmp/_output
> >
> > Although I do get both outputs, the screen looses all colorized output
... but again, if I do it this way the output to the screen goes B&W.
> There is nothing intrinsic to your construct that loses colour escape
> sequences. Try the following:
>
>    eval "print -P '%K{blue}Hello'" >&2 >! /tmp/_output
>    cat /tmp/_output
>
> This should give you a blue background from both commands.
Right, so it does.
> So you might need to take a closer look at exactly what argument you are
> passing to eval.
>
> Some commands, make coloured output conditional on whether their
> standard output points to a terminal. For an example, try:
>    git log | cat

Maybe that's it.  So is 'aptitude' or 'egrep' itself determining that 
color is not to be had due to the double output?  Sounds likely, I know 
that the greps all behave differently when receiving piped input than 
when not.  And I'm correct that if one output is modified the other will 
be too?

Thanks, I'll play with it a bit more.
=======================
> Oliver