Re: RFT: Request for a trick :O)

[Meino Christian Cramer <Meino.Cramer@gmx.de>]

From: Peter Stephenson <pws@csr.com>
Subject: Re: RFT: Request for a trick :O) 
Date: Mon, 08 Aug 2005 11:41:29 +0100

Hi,

 thanks for all the help ! :)

 I did not need the exact position and byte counts of differing bytes
 at all. I only need a "yes" or "no" whether I have identical file
 (and can delete the doublettes).

 I saw this "broken pipe"-thingy and didnt dare to delete files on the
 base of this...I thought I did something very wrong (I amstill a very
 new zsher ;).

 "Broken pipe" means: different files.
 
 Ok...if my memory serves me right...the return status of the last
 command in a pipe is the return status of the whole pipe, isn't it ?

 But unfortunately, the cmp is the first command in that construction... 

 I think with something like  

   function zipcmp ()
   {
	  	cmp <(7z x -so $1 2>/dev/null ) <(7z x -so $2 2>/dev/null )		
   }
   
   if [ ! zipcmp $1 $2 ]
   then
      rm -f $1
   fi

 I mostly would get an empty harddisc.... ;)

 How can I get the return code of cmp, if <( is implemented as a pipe
 ?

 Keep zshing!
 Meino
 

> Stephane Chazelas wrote:
> > > >     Extracting  GlassBowl001.blend/usr/bin/7z: line 2:  5488 Broken pipe
> > > >           /usr/lib/p7zip/7z "$@"
> > > >     Extracting  GlassBowl001.blend/usr/bin/7z: line 2:  5492 Broken pipe
> > > >           /usr/lib/p7zip/7z "$@"
> > > 
> > 
> > I think it's rather because cmp stops reading at the first
> > difference -> so exit -> so close the pipes -> so the feeders
> > get a SIGPIPE.
> > 
> > That's normal and expected, you'd get the same with:
> > 
> > 7z ... | cmp - other-file
> 
> You're right.  I'd assumed the files were actually identical, but reading
> back I see Meino did say they weren't.  The "broken pipe" is simply a
> detail of the implementation of the <( ... ).
> 
> Meino, if you want a full comparison to the end of the file, you can
> use "cmp -l", which will give lots of output.  Otherwise, you can redirect
> 2>/dev/null in the p7zip command.
> 
> pws
> 
> 
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