scripter87 has asked for the wisdom of the Perl Monks concerning the following question:

hi guys can anyone advise me on this piece of code. 
 #!/usr/bin/perl
use strict;
use warnings;
my $filename = "filet.txt";
my $emailRE='/(\b[\w\.@]+\b)/';
my @emails=();
 my $email;
  my $mail;
while (<>) #for each line in each file
{
@emails = (/($emailRE)/og); #get all the emails on this line

foreach $email (@emails)
{ print "$email, $.\n"; 
open(FILE, ">$filename") or die "Can't write to $filename: $!";
print FILE $email;
} # print them out
#close FILE;
}

[download]

So I am trying to extract data from a file that I use as an argument on the command line. When I print to the screen it shows the extracted information in "$email". I then open the file that I wanted to write to and write "$email" to it but it does not contain all the data that it should i.e. the information seen when I print screen has lot more than what my written file shows.

Replies are listed 'Best First'.
Re: extracting from 1 file and adding to another.
by Corion (Patriarch) on Oct 19, 2013 at 12:01 UTC

    I really recommend you use proper indentation for your blocks. This will make the error quite obvious. Indent the content of each block by four spaces:

    #!/usr/bin/perl
use strict;
use warnings;
my $filename = "filet.txt";
my $emailRE='/(\b[\w\.@]+\b)/';
my @emails=();
my $email;
my $mail;
while (<>) #for each line in each file
{
    @emails = (/($emailRE)/og); #get all the emails on this line

    foreach $email (@emails)
    {
        print "$email, $.\n"; 
        open(FILE, ">$filename") or die "Can't write to $filename: $!"
+;
        print FILE $email;
    } # print them out
    #close FILE;
}

    [download]

    As a second step, I recommend printing out the progress of your program. For example, add a warn statement when you open your output file.

    Also, you may want to learn about the arguments to open. Especially take a look at what > means - it means create-and-overwrite.

[reply]
[d/l]
[select]
      Sorry about the indentation.. trying so many different things at the moment and it got messy. Yes I dont plan to append to the output file just yet. But given I got more than ten or more lines when I printed out "$email" to screen, I would of expected the same to be on the file I had written.
[reply]

        You don't even have to do the indentation manually, Perl::Tidy will do it for you: $ perltidy your-script.pl (output goes to your-script.pl.tdy). Also, you can get some useful information from Perl::Critic: 

        $ perlcritic your-script.pl
Loop iterator is not lexical at line 13, column 1.  See page 108 of PB
+P.  (Severity: 5)
Bareword file handle opened at line 15, column 1.  See pages 202,204 o
+f PBP.  (Severity: 5)
Two-argument "open" used at line 15, column 1.  See page 207 of PBP.  
+(Severity: 5)

        [download]

        Update: As for your concrete problem, can you supply some (scrambled) input data?

        Well done is better than well said. -- Benjamin Franklin

[reply]
[d/l]
[select]
        Spot on for that ">" nudge. But I seem to missing the concept of it... I thought using >> was to add on to a file without overwriting. Didnt think it was necessary for the first file write. I still dont have it right but using that method atleast adds a bit more to my file.
[reply]

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