Re: Getting xfilter AND delivery to working

On Fri, 05 Feb 2016 00:34:36 +1100
Philip Rhoades <[email protected]> wrote:

> Milan,
> 
> On 2016-02-04 20:39, Milan Obuch wrote:
> > On Thu, 04 Feb 2016 19:14:24 +1100
> > Philip Rhoades <[email protected]> wrote:
> >   
> >> People,
> >> 
> >> I have this filter:
> >> 
> >> if( /^[TC][[co]:.*tst/ )
> >> {
> >>      xfilter "/home/phil/bin/bash_internal_variables.sh  
> >> > /home/phil/t" to $DEFAULT/.tst/  
> >> }
> >> 
> >> and the xfilter is working but the delivery is not - if I reverse
> >> the lines, the delivery works but the xfilter does not - how can I
> >> get BOTH lines to work?
> >>   
> > 
> > Hi,
> > 
> > did zou examine your mailogs? Maybe there is a clue...  
> 
> No errors or anything unusual . .
> 
> > Also, could you
> > show us what's there in /home/phil/bin/bash_internal_variables.sh
> > file?  
> 
> #!/bin/bash
> 
> echo -n "!                | " ;	echo $!

[ snip ]

> echo -n "time             | " ;	echo $time
> 
> but why should anything in there matter?  Even if an error code was 
> returned, maildrop should still execute the "to" command?
> 

[ snip ]

I did some tests and now I can confirm your observation. Here is my
explanation.

First, quote from 'man maildropfilter':

       xfilter - filter message through another program
               xfilter expression


           expression specifies an external program that maildrop runs
           to filter the current message. The current message will be
           piped to the filter program as standard input. The output of
           the filter program replaces the current message being
           delivered. The external program must terminate with an exit
           code of 0. If the external program does not terminate with
           an exit code of 0, or if it does not read the message from
           the standard input, maildrop terminates with an exit code of
           EX_TEMPFAIL.

Applied to your example, simplified, line

xfilter "/home/phil/bin/bash_internal_variables.sh > /home/phil/t"

makes output of command "/home/phil/bin/bash_internal_variables.sh
> /home/phil/t" new message content. As your redirected stdout to file,
there is no output, which means effectively you deleted the whole
message content. Courier sees that and does nothing, as there is
nothing to deliver.

I think your misused xfilter command. It looks like what you want to do
is some environment logging for testing. Try to use backticks, excerpt
from the same 'man maildropfilter':

   Command substitution
       Text enclosed in back-tick characters is interpreted as a shell
       command. The shell command is executed as a child process by
       maildrop. Its output is used in place of the command. For
       example:

           DIR=`ls`

       places the names of the files in the current directory into the
       DIR variable.

       The output of the command will have all newline characters
       replaced by spaces, and leading and trailing spaces will be
       stripped (multiple spaces are not removed, though). Also, the
       contents of the message being delivered is made available to the
       command on standard input.

Here the message is not overwritten, so line next is executed normally.
So, your test code would be

`/home/phil/bin/bash_internal_variables.sh > /home/phil/t`

instead of

xfilter "/home/phil/bin/bash_internal_variables.sh > /home/phil/t"

Hope this helps.

Milan

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