anchor.diff:    '';
   
     installPhase = ''
  -    datadir=/nix/var/lib/arb
       ensureDir $out/lib
  -    # link out shared location
  -    ensureDir $datadir/lib/pts
  -    chmod a+rwx $datadir/lib/pts
  -    # cp -vau lib/pts $datadir/lib
  +    shareddir=/nix/var/lib/arb
  +    # link out writable shared location lib/pts
  +    ensureDir $shareddir/lib/pts
  +    cp -vau lib/pts $shareddir/lib
       rm -vrf lib/pts
  -    ln -vs $datadir/lib/pts $out/lib/pts
  -    # link out shared location
  -    ensureDir $datadir/lib/nas
  -    cp -vau lib/nas $datadir/lib
  +    ln -vs $shareddir/lib/pts $out/lib/pts
  +    chmod a+rw -R $shareddir/lib/pts
  +    # link out writable shared location lib/nas/
  +    ensureDir $shareddir/lib/nas
  +    cp -vau lib/nas $shareddir/lib
       rm -vrf lib/nas
  -    ln -vs $datadir/lib/nas $out/lib/nas
  +    ln -vs $shareddir/lib/nas $out/lib/nas
  +    chmod a+rw -R $shareddir/lib/nas
  +    # link out shared lib/pixmaps (not sure about this, yet):
  +    ensureDir $shareddir/lib/pixmaps
  +    cp -vau lib/pixmaps $shareddir/lib
  +    rm -vrf lib/pixmaps
  +    ln -vs $shareddir/lib/pixmaps $out/lib/pixmaps
  +    chmod a+rw -R $shareddir/lib/pixmaps
       # bulk copy
       cp -vau * $out
       # replace arb script
  
positive.code: 
    meta = {
      description     = "ARB software for sequence database handling and analysis";
      longDescription = ''The ARB software is a graphically oriented package comprising various tools for sequence database handling and data analysis. A central database of processed (aligned) sequences and any type of additional data linked to the respective sequence entries is structured according to phylogeny or other user defined criteria''; 
      license     = "non-free";
      pkgMaintainer = "Pjotr Prins";
      homepage    = http://www.arb-home.de/;
    };
  }
  
negative.code: #!/bin/sh
  
  echo Starting Nix compiled arb from $out
  echo Shared databases are located in $shareddir
  # sometimes local profiles override these:
  export ARBHOME=$out
  export LD_LIBRARY=$ARBHOME/lib   
  
  $out/bin/arb_ntree $*
  
  