[debbugs-tracker] bug#20837: closed (Code for --color=auto)

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Your message dated Sat, 18 Jul 2015 17:13:38 -0700
with message-id <address@hidden>
and subject line Re: Code for --color=auto
has caused the debbugs.gnu.org bug report #20837,
regarding Code for --color=auto
to be marked as done.

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20837: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=20837
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> --- Begin Message ---
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> Subject: 
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> Code for --color=auto
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>
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> Date: 
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> Wed, 17 Jun 2015 07:08:23 -0700
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>
> Hello -
>
> I have my own C program where I also use SGR to produce color just like grep 
> does.  I pulled the grep source (2.21) to see how —color=auto was implemented.  
> In grep.c, lines 2440-2441, there is the code:
>
>         if (color_option == 2)
>           color_option = isatty (STDOUT_FILENO) && should_colorize ();
>
> The thing about using isatty() is that it doesn’t work for the common case of 
> piping the output of grep to less.  What about using fstat(STDOUT_FILENO) 
> instead?  From testing (where “C” is an C program that outputs color using 
> SGR), I’ve gotten:
>
>         COMMAND  Should? isatty ISCHR ISFIFO ISREG
>         ======== ======= ====== ===== ====== =====
>         C          T      T      T     F      F
>         C > file   F      F      F     F    >>T<<---- The interesting case.
>         C | less   T      F      F     T      F
>
> Hence, it would seem that we want to output color except when ISREG on the stat 
> struct on stdout is T.  Wouldn’t this make better logic for —color=auto ?
>
> - Paul
>
>
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
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> Re: Code for --color=auto
>
>
>
>
> Date: 
>
> Sat, 18 Jul 2015 17:13:38 -0700
>
>
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>
> User-agent: 
>
> Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0
>
>
>
>
> This one's an easy call: the current behavior for --color=auto was designed to 
> work the way it does, for the reasons Eric explained.  Closing the bug report, 
> as it's not a bug.
>
>
> --- End Message ---