Vineet Pande wrote:
> hi,
Hello,
> In the following code which reads a file.txt (SEE ATTACHMENT) where I am
> trying to understand how to put the DNA sequence in to a single string...
>
> print "enter file with DNA sequence: ";
> $seqfile = <STDIN>;
> chomp $seqfile;
> unless ( open(DNAFILE, $seqfile) )
> {
> print "can't open!!\n";
> exit;
> }
> @dna = <DNAFILE>;
> close DNAFILE;
>
> $dna = join( '', @dna);
> print "$dna\n";
>
> THE OUTPUT IS EXACTLY THE SAME AS IN file.txt.....Why don't we get the
> string joined...of course i agree i must clean whitespace...bu then what
> is expected out of join( '', ....). WHAT '' means?
'' is just a(n empty) string.
$x = join '', 'string1', 'string2', 'string3';
Is the same as:
$x = 'string1' . '' . 'string2' . '' . 'string3';
Which is the same as:
$x = 'string1' . 'string2' . 'string3';
In your case you can concatenate directly to $dna without using an array:
my $dna;
while ( <DNAFILE> ) {
$dna .= $_;
}
print "$dna\n";
Or the usual perl way to do it (by undefining the input record separator):
my $dna = do { local $/; <DNAFILE> };
print "$dna\n";
John
--
use Perl;
program
fulfillment
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