It’s in the package “Bioperl“->”Bio::SeqIO“.
1.open file
my $io = Bio::SeqIO->new(-file => "noN.fa",-format =>"fasta");2. readin one sequence
my $record = $io -> next_seq;3. variable
$record->id; #identifier
$record->desc; #description
$record->length; #length of this sequence
$record->seq; #sequence