dovecot - Mar 2015 - Patch for "doveadm -f table" nit (was Re: Dovecot current number of connections being used.)

> doveadm who -1 2>/dev/null | wc -l
You have to redirect stderr to /dev/null because that's where the
first header line is written to.  The default format style (table)
is inconsistent with the other formats (flow,pager,tab) that write
headers and data to stdout.

The following patch will pick this nit.  This patch will require
modifications to scripts that rely on doveadm writing headers to stderr.
For example, the above doveadm command could be modified to

 	doveadm who -1 | grep -vc '^username'

--------------------------------------------------------------------------------
--- a/dovecot-2.2.16.rc1/src/doveadm/doveadm-print-table.c	Wed Mar 18 15:40:40
2015
+++ b/dovecot-2.2.16.rc1/src/doveadm/doveadm-print-table.c	Wed Mar 18 15:41:18
2015
@@ -151,3 +151,3 @@
  	for (i = 0; i < count; i++) {
-		if (i > 0) fprintf(stderr, " ");
+		if (i > 0) printf(" ");

@@ -155,3 +155,3 @@
  		     DOVEADM_PRINT_HEADER_FLAG_RIGHT_JUSTIFY) == 0) {
-			fprintf(stderr, "%-*s", (int)headers[i].length,
+			printf("%-*s", (int)headers[i].length,
  				headers[i].title);
@@ -158,3 +158,3 @@
  		} else {
-			fprintf(stderr, "%*s", (int)headers[i].length,
+			printf("%*s", (int)headers[i].length,
  				headers[i].title);
@@ -162,3 +162,3 @@
  	}
-	fprintf(stderr, "\n");
+	printf("\n");
  }
--------------------------------------------------------------------------------

Joseph Tam <jtam.home at gmail.com>

On 19 Mar 2015, at 02:37, Joseph Tam <jtam.home at gmail.com>
wrote:
> 
> 
>> doveadm who -1 2>/dev/null | wc -l
> 
> You have to redirect stderr to /dev/null because that's where the
> first header line is written to.  The default format style (table)
> is inconsistent with the other formats (flow,pager,tab) that write
> headers and data to stdout.
> 
> The following patch will pick this nit.  This patch will require
> modifications to scripts that rely on doveadm writing headers to stderr.
> For example, the above doveadm command could be modified to
> 
> 	doveadm who -1 | grep -vc '^username'
There's no reason why flow and pager should write headers to stderr because
it would always result only in a mess. But instead of changing table headers to
write to stdout, I think a better fix would be to make tab formatter write
headers to stderr. Including headers in stdout makes it more difficult to write
scripts that access the actual data. For example now you can do "doveadm
who -1 | sort" and the output will work. If headers were written to stdout
you'd have to make it more complicated. Also you can now easily specify what
you want to do with the headers, 2>/dev/null if you don't care about them
or 2>&1 if you want to include them in stdout (which works even after
|sort).

So, I'll add in my v2.3 TODO that tab formatter should write to stderr..

On Thu, 19 Mar 2015, Timo Sirainen wrote:
>> You have to redirect stderr to /dev/null because that's where the
>> first header line is written to.  The default format style (table)
>> is inconsistent with the other formats (flow,pager,tab) that write
>> headers and data to stdout.
>
> There's no reason why flow and pager should write headers to stderr
> because it would always result only in a mess.
Right.
> But instead of changing table headers to write to stdout, I think a
> better fix would be to make tab formatter write headers to stderr.
That would at least make the behaviour consistent.
> Including headers in stdout makes it more difficult to write scripts
> that access the actual data.  For example now you can do "doveadm who
> -1 | sort" and the output will work.  If headers were written to
stdout
> you'd have to make it more complicated.  Also you can now easily
> specify what you want to do with the headers, 2>/dev/null if you
don't
> care about them or 2>&1 if you want to include them in stdout (which
> works even after |sort).
I agree with the easier parsing thing for scripts.  It just a little
weird when you're doing piping interactively and the header pops out.
Another option is to add another flag/formatter that will squelch headers.

I'm cool with whatever you implement.

Joseph Tam <jtam.home at gmail.com>

On 03/18/2015 08:49 PM, Timo Sirainen wrote:
> There's no reason why flow and pager should write headers to stderr
because it would always result only in a mess. But instead of changing table
headers to write to stdout, I think a better fix would be to make tab formatter
write headers to stderr. Including headers in stdout makes it more difficult to
write scripts that access the actual data. For example now you can do
"doveadm who -1 | sort" and the output will work. If headers were
written to stdout you'd have to make it more complicated. Also you can now
easily specify what you want to do with the headers, 2>/dev/null if you
don't care about them or 2>&1 if you want to include them in stdout
(which works even after |sort).
>
> So, I'll add in my v2.3 TODO that tab formatter should write to
stderr..
I've been using "-f flow fetch text | sed s/^text=//" when
training
spamassasin. Couldn't find a straightforward 'fetch raw message'.
Seems
unnecessarily awkward. Moving headers to stderr would help this, though.