script to check the size of given contig

Question

[div]

can anyone please tell me the script to check the size of the each given contig (contigs are in multi-fasta format).

[Ashutosh Pandey]

This looks like a HW question. Don't give up easily and try some more :-). I assure you that you would enjoy the whole learning process. You can search for a few posts here on Biostar for help. Search for "length fasta sequences".

[Pierre Lindenbaum]

+1 A. Pandey. See also Code Golf: Mean Length Of Fasta Sequences

Answer 1

[biolab]

I provide a perl solution as follows (usage: perl length.pl fastafile).

#!/usr/bin/perl
use strict;
use warnings;
open my $fasta_file, '<', $ARGV[0] or die $!;
my ($id, $seq);
while (<$fasta_file>) {
    chomp;
    if (/^>(\S+).*/) {
        print "$id\t", length($seq), "\n" if defined $id;
        $id = $1;
        $seq = '';
    } else {
        $seq .= $_;
    }
}
close $fasta_file;
print "$id\t", length($seq), "\n";

[div]

Thank you all for reply..:)

Reply for biolab : thank u so much.....:) it worked...:)

Answer 2

[rtliu]

From bioawk tutorial - https://github.com/vsbuffalo/bioawk-tutorial

bioawk -cfastx '{print $name, length($seq)}' test.fasta

Answer 3

[Paul]

Hi, try awk solution:

for i in *.fa

 do awk 'BEGIN{RS=">"}NR>1{sub("\n","\t"); gsub("\n",""); print RS$0}' $i > ${i%.fasta}.column.csv

  awk 'length($2) {print $1 "\t" length}' ${i%.fasta}.column.csv | sort -k 2n > ${i%.fasta}.csv

 done;

Or you can put second awk command to pipe for avoiding create *column.csv file.