From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [iproute PATCH 4/4] lib: Enable colored output only for TTYs
Date: Wed, 15 Aug 2018 08:04:06 -0700
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        <20180815090610.16646-5-phil@nwl.cc>
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Cc: Phil Sutter <phil@nwl.cc>, netdev@vger.kernel.org,
        Till Maas <opensource@till.name>
To: David Ahern <dsahern@gmail.com>
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On Wed, 15 Aug 2018 08:40:20 -0600
David Ahern <dsahern@gmail.com> wrote:

> On 8/15/18 3:06 AM, Phil Sutter wrote:
> > Add an additional prerequisite to check_enable_color() to make sure
> > stdout actually points to an open TTY device. Otherwise calls like
> >=20
> > | ip -color a s >/tmp/foo
> >=20
> > will print color escape sequences into that file.
> >=20
> > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > ---
> >  lib/color.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >=20
> > diff --git a/lib/color.c b/lib/color.c
> > index edf96e5c6ecd7..500ba09682697 100644
> > --- a/lib/color.c
> > +++ b/lib/color.c
> > @@ -3,6 +3,7 @@
> >  #include <stdarg.h>
> >  #include <stdlib.h>
> >  #include <string.h>
> > +#include <unistd.h>
> >  #include <sys/socket.h>
> >  #include <sys/types.h>
> >  #include <linux/if.h>
> > @@ -79,7 +80,7 @@ void enable_color(void)
> > =20
> >  int check_enable_color(int color, int json)
> >  {
> > -	if (color && !json) {
> > +	if (color && !json && isatty(fileno(stdout))) {
> >  		enable_color();
> >  		return 0;
> >  	}
> >  =20
>=20
> This also disables color sequence when the output is piped to a pager
> such as less which with the -R argument can handle it just fine.
>=20
> ie., the user needs to remove the color arg when that output is not wante=
d.

If you are going to change the color enabling, why not make it compatible
with what ls does?

=46rom man ls(1) (and  grep)

       --color[=3DWHEN]
              colorize  the output; WHEN can be 'always' (default if omitte=
d),
              'auto', or 'never'; more info below
...

       Using  color  to distinguish file types is disabled both by default =
and
       with --color=3Dnever.  With --color=3Dauto, ls emits color codes onl=
y  when
       standard  output is connected to a terminal.  The LS_COLORS environm=
ent
       variable can change the settings.  Use the dircolors command to set =
it.


Make -c be same as --color=3Dalways to keep compatiablity