Is this possible with MULTIOS

Is this possible with MULTIOS

[Meino Christian Cramer]

Hi,

 I have several cvs/svn-snapshots on my hd, which I update on a
 regular basis. 

 Sometimes not all snapshots are update.

 Currently my script, which does the cvs/svn updates, pipes the output
 of the according cvs/svn-command through a filter to echo all lines,
 which signals, that files have been uopdated/merged/modifed etc to
 stdout. I have to watch the output to decide whether I want to
 recompile the source.

 What I want is something like:

 upcnt=`<update-cmd> | <filter> | wc -l`
 if [ 0 -ne upcnt ]
 then
  <recompile source
 else
  echo "No file has been changed!"
 fi

 BUT!
 "<filter>" should still print all lines which signal changes to files
 to the terminal....


 Unfortunately the "| wc -l"-part catches stdout and supress echoing
 those lines that way.

 "tee" seems no to work here, since it copies stdout to a _file_ and I
 want to avoid writing temporary files.....it seems I need something
 like two stdouts here...

 Or may be I had thought for too long about this so I don't see the (for
 others) obvious solution ???

 Any light against my blindness ??? ;))))

 Keep hacking and thank you very much for any help in advance !
 Have a nice weekend!
 mcc


 

Re: Is this possible with MULTIOS

[Bart Schaefer]

On Oct 22,  4:16pm, Meino Christian Cramer wrote:
} 
}  upcnt=`<update-cmd> | <filter> | wc -l`
}  if [ 0 -ne upcnt ]

If the filter is grep, it exits with a success code when it finds a
matching line or with failure when it does not, so you should be able
to do 

  if update-cmd | grep ...
  then recompile
  else ...
  fi

This would behave differently only if grep matched some lines and then
exited with an error.

However, to answer your literal question, yes, you can do this with
multios.  You just have to open an extra descriptor outside of the
subshell and redirect stdout to it inside the subshell.

  setopt multios
  uncnt=$(update-cmd | filter 1>&3 | wc -l) 3>&1

Re: Is this possible with MULTIOS

[Meino Christian Cramer]

From: Bart Schaefer <schaefer@brasslantern.com>
Subject: Re: Is this possible with MULTIOS
Date: Sun, 22 Oct 2006 19:30:54 -0700

> On Oct 22,  4:16pm, Meino Christian Cramer wrote:
> } 
> }  upcnt=`<update-cmd> | <filter> | wc -l`
> }  if [ 0 -ne upcnt ]
> 
> If the filter is grep, it exits with a success code when it finds a
> matching line or with failure when it does not, so you should be able
> to do 
> 
>   if update-cmd | grep ...
>   then recompile
>   else ...
>   fi
> 
> This would behave differently only if grep matched some lines and then
> exited with an error.
> 
> However, to answer your literal question, yes, you can do this with
> multios.  You just have to open an extra descriptor outside of the
> subshell and redirect stdout to it inside the subshell.
> 
>   setopt multios
>   uncnt=$(update-cmd | filter 1>&3 | wc -l) 3>&1
> 

Hi Bart,

 *thanks a lot* :)

 Both solutions will help me !

 Have a nice week!
 mncc