How can I extract numeric data from a text file? - perl

Question

I want the Perl script to extract a data from a text file and save it as another text file. Each line of the text file contains an URL to a jpg like "http://pics1.riyaj.com/thumbs/000/082/104//small.jpg". I want the script to extract the last 6 numbers of each jpg URL, (i.e 082104) to a variable. I want the variable to be added to a different location on each line of the new text.
Input text:
text http://pics1.riyaj.com/thumbs/000/082/104/small.jpg text
text http://pics1.riyaj.com/thumbs/000/569/315/small.jpg text
Output text:
text php?id=82104 text
text php?id=569315 text
Thanks

Answer 1

What have you tried so far?
Here's a short program that gives you the meat of the problem, and you can add the rest of it:
while( )
{
s|http://.*/\d+/(\d+)/(\d+).*?jpg|php?id=$1$2|;
print;
}
This is very close to the command-line program the handles the looping and printing for you with the -p switch (see the perlrun documentation for the details):
perl -pi.old -e 's|http://.*/\d+/(\d+)/(\d+).*?jpg|php?id=$1$2|' inputfile > outputfile

Answer 2

I didn't know whether to answer according to what you described ("last 6 digits") or just assume that it all fits the pattern you showed. So I decided to answer both ways.
Here is a method that can handle lines more diverse than your examples.
use FileHandle;
my $jpeg_RE = qr{
(.*?) # Anything, watching out for patterns ahead
\s+ # At least one space
(?> http:// ) # Once we match "http://" we're onto the next section
\S*? # Any non-space, watching out for what follows
( (?: \d+ / )* # At least one digit, followed by a slash, any number of times
\d+ # another group of digits
) # end group
\D*? # Any number of non-digits looking ahead
\.jpg # literal string '.jpg'
\s+ # At least one space
(.*) # The rest of the line
}x;
my $infile = FileHandle->new( "<$file_in" );
my $outfile = FileHandle->new( ">$file_out" );
while ( my $line = <$infile> ) {
my ( $pre_text, $digits, $post_text ) = ( $line =~ m/$jpeg_RE/ );
$digits =~ s/\D//g;
$outfile->printf( "$pre_text php?id=%s $post_text\n", substr( $digits, -6 ));
}
$infile->close();
However, if it's just as regular as you show, it gets a lot easier:
use FileHandle;
my $jpeg_RE = qr{
(?> \Qhttp://pics1.riyaj.com/thumbs/\E )
\d{3}
/
( \d{3} )
/
( \d{3} )
\S*?
\.jpg
}x;
my $infile = FileHandle->new( "<$file_in" );
my $outfile = FileHandle->new( ">$file_out" );
while ( my $line = <$infile> ) {
$line =~ s/$jpeg_RE/php?id=$1$2/g;
$outfile->print( $line );
}
$infile->close();