Subject: Re: [PATCH v5 1/2] add-patch: do not show UI messages on stderr

From: Rubén Justo <[email-masked]>
Date: Tue, 30 Apr 2024 18:35:12 +0200

On Tue, Apr 30, 2024 at 06:52:56AM -0400, Jeff King wrote:
> On Mon, Apr 29, 2024 at 12:24:46PM -0700, Junio C Hamano wrote:
> 
> > Rubén Justo <[email-masked]> writes:
> > 
> > > diff --git a/add-patch.c b/add-patch.c
> > > index 0997d4af73..fc0eed4fd4 100644
> > > --- a/add-patch.c
> > > +++ b/add-patch.c
> > > @@ -293,10 +293,9 @@ static void err(struct add_p_state *s, const char *fmt, ...)
> > >  	va_list args;
> > >  
> > >  	va_start(args, fmt);
> > > -	fputs(s->s.error_color, stderr);
> > > -	vfprintf(stderr, fmt, args);
> > > -	fputs(s->s.reset_color, stderr);
> > > -	fputc('\n', stderr);
> > > +	fputs(s->s.error_color, stdout);
> > > +	vprintf(fmt, args);
> > > +	puts(s->s.reset_color);
> > 
> > I like the attention of the detail here ;-).
> 
> Indeed. I had to read this several times to wonder why it was not a
> mistake to leave the first fputs() but use vprintf() and puts() for the
> other two (for those just reading, the answer is that puts() prints an
> extra newline, so we can only use it at the end).

I did not know the details (or had happily forgotten them) but Junio
ignoring my comments in [1] intrigued me :-).  A simple test would have
been quick, but "man puts" was quicker;  my comments were not correct.

Just to be clear, and to extend your comment, in case any reader is
interested, this:

	vfprintf(stdout, fmt, args);

can be written as follows:

	vprintf(fmt, args);

And this:

	fputs(s->s.reset_color, stdout);
	fputc('\n', stdout);

can be shortened to:

	puts(s->s.reset_color);

The difference in vfprintf and vprintf is quite obvious IMHO, but not so
obvious with puts.  The documentation says:

  SYNOPSIS

       int puts(const char *s);

  DESCRIPTION

       puts() writes the string s and a trailing newline to stdout.

  [1] - https://lore.kernel.org/git/[email-masked]/T/#m644a682364212729a2b21c052ef744039c26f972