Hi, I am trying to right a tool that will generate 2 ouptuts, 1 .txt and .gz. Before the tools runs I don't know how many fasta files will be in the .gz file. I have managed to have the perl script writing files like follow : $seqio_obj = Bio::SeqIO->new(-file => $seq_library_name, -format => "fasta" ); while ($seq_obj = $seqio_obj->next_seq) { $seq_ID = $seq_obj -> display_id; $seq = $seq_obj -> seq; #print $seq_ID."\n"; #print $MID_id_ref{$seq_ID}."\n"; if (defined($combination{$seq_ID})) { open(OUT,">>/my/own/path/on/my/server/which /is/not/good/".$combination{$seq_ID}."_library.fasta")||die"Pb ouverture du fichier3"; print OUT ">".$seq_ID."\n".$seq."\n"; #open(OUT,">>".$output_name2)||die"Pb ouverture du fichier3"; #print OUT ">".$seq_ID."\n".$seq."\n"; } else { open(OUT,">>/my/own/path/on/my/server/which /is/not/good/unsorted_library.fasta")||die"Pb ouverture du fichier3"; print OUT ">".$seq_ID."\n".$seq."\n"; #open(OUT,">>".$output_name2)||die"Pb ouverture du fichier3"; #print OUT ">".$seq_ID."\n".$seq."\n"; $nb_unsorted_seq++; } $nb_total_seq++; } I then use a command line to zip as follow : system('cd $work_dir'); system('tar -zcPf '.$output_name2.' /my/own/path/on/my/server/which /is/not/good/'); If one of you have encounter the same problem or if you can point me to a tool which is doing some similar stuff. Thanks, Philippe