The London Perl and Raku Workshop takes place on 26th Oct 2024. If your company depends on Perl, please consider sponsoring and/or attending.


Bio::SeqIO::tab - nearly raw sequence file input/output stream. Reads/writes id"\t"sequence"\n"


Do not use this module directly. Use it via the Bio::SeqIO class.


This object can transform Bio::Seq objects to and from tabbed flat file databases.

It is very useful when doing large scale stuff using the Unix command line utilities (grep, sort, awk, sed, split, you name it). Imagine that you have a format converter 'seqconvert' along the following lines:

  my $in  = Bio::SeqIO->newFh(-fh => \*STDIN , '-format' => $from);
  my $out = Bio::SeqIO->newFh(-fh=> \*STDOUT, '-format' => $to);
  print $out $_ while <$in>;

then you can very easily filter sequence files for duplicates as:

  $ seqconvert < foo.fa -from fasta -to tab | sort -u |\
       seqconvert -from tab -to fasta > foo-unique.fa

Or grep [-v] for certain sequences with:

  $ seqconvert < foo.fa -from fasta -to tab | grep -v '^S[a-z]*control' |\
       seqconvert -from tab -to fasta > foo-without-controls.fa

Or chop up a huge file with sequences into smaller chunks with:

  $ seqconvert < all.fa -from fasta -to tab | split -l 10 - chunk-
  $ for i in chunk-*; do seqconvert -from tab -to fasta < $i > $i.fa; done
  # (this creates files chunk-aa.fa, chunk-ab.fa, ..., each containing 10
  # sequences)


Mailing Lists

User feedback is an integral part of the evolution of this and other Bioperl modules. Send your comments and suggestions preferably to one of the Bioperl mailing lists. Your participation is much appreciated.                  - General discussion  - About the mailing lists


Please direct usage questions or support issues to the mailing list:

rather than to the module maintainer directly. Many experienced and reponsive experts will be able look at the problem and quickly address it. Please include a thorough description of the problem with code and data examples if at all possible.

Reporting Bugs

Report bugs to the Bioperl bug tracking system to help us keep track the bugs and their resolution. Bug reports can be submitted via the web:


Philip Lijnzaad,


The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _


 Title   : next_seq
 Usage   : $seq = $stream->next_seq()
 Function: returns the next sequence in the stream
 Returns : Bio::Seq object
 Args    :


 Title   : write_seq
 Usage   : $stream->write_seq($seq)
 Function: writes the $seq object into the stream
 Returns : 1 for success and 0 for error
 Args    : Bio::Seq object