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How can one use the print function to get the correct information?

by supriyoch_2008 (Scribe)
on Apr 05, 2013 at 17:58 UTC ( #1027184=perlquestion: print w/ replies, xml ) Need Help??
supriyoch_2008 has asked for the wisdom of the Perl Monks concerning the following question:

Hi PerlMonks,

I am interested to get the detailed information of the student using print function in the following script i.e. 3.pl so that the information can be printed easily on a text page. When I have used the scalar variable $result1, I have got wrong result i.e. 1. I am looking forward to Perl Monks for suggestions. I am at my wit's end to get the desrired result using print function.

Here goes the input file: rc.txt

A:50:r1 B:45:r2 C:40:r3

The script 3.pl is given below:

use warnings; use strict; ######################## # DATABASE Input: ### #################################################### print "\n\n Please ENTER Database Name (.txt): "; my $DNAfilename=<STDIN>; chomp $DNAfilename; # open the file, or exit: unless (open(DNAFILE, $DNAfilename) ) { print "Cannot open file \"$DNAfilename\"\n\n"; exit;} my @DNA= <DNAFILE>; print"\n $DNAfilename Database:\n\n"; print @DNA; print"\n"; ########################## ## CODE STARTS HERE: ########################## {package Student; sub new { my ($class, $name, $age, $regd_no)=@_; my $objref={ NAME => $name, AGE => $age, REGD_NO => $regd_no }; return bless $objref, $class;} sub display { my ($self) = @_; if ($self) { print ' Student Name: ', $self->{NAME}, "\n"; print ' Age (yr): ', $self->{AGE}, "\n"; print ' Regd no: ', $self->{REGD_NO}, "\n"; } } } my @students; open (DNAFILE, '<', $DNAfilename) or die "Perl says $!"; while (<DNAFILE>) { chomp; push @students, Student->new(split /:/); } print"\n WELCOME to Students' Database:\n"; print"\n Enter the Registration Number to view the details: "; my $reg=<STDIN>; chomp $reg; my $result1=(find_student($reg)->display()); print"\n Detailed Information for Registration No. $reg:\n $result1\n"; sub find_student {my ($regd_no) = @_; print"\n\n"; print"\n The details of the Regn No. $reg are:\n\n"; for (@students) { return $_ if $_->{REGD_NO} eq $regd_no; } return undef; } print"\n\n"; exit;

The cmd shows wrong result as shown below:

Microsoft Windows [Version 6.1.7600] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\x>cd desktop C:\Users\x\Desktop>3.pl Please ENTER Database Name (.txt): rc.txt rc.txt Database: A:50:r1 B:45:r2 C:40:r3 WELCOME to Students' Database: Enter the Registration Number to view the details: r1 The details of the Regn No. r1 are: Student Name: A Age (yr): 50 Regd no: r1 Detailed Information for Registration No. r1: 1 # WRONG RESULT C:\Users\x\Desktop>

Comment on How can one use the print function to get the correct information?
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Re: How can one use the print function to get the correct information?
by Corion (Pope) on Apr 05, 2013 at 18:05 UTC

    Consult the print documentation to learn about the return value of the print function.

    If you want to construct a string for further processing, don't use print. Just construct the string and return it.

Re: How can one use the print function to get the correct information?
by CountOrlok (Friar) on Apr 05, 2013 at 18:07 UTC
    Try changing:
    my $result1=(find_student($reg)->display());
    to:
    my $result1 = find_student($reg)->display();
    Update: As golux mentioned, your display function is not returning anything useful.
Re: How can one use the print function to get the correct information?
by golux (Pilgrim) on Apr 05, 2013 at 18:08 UTC
    Hi supriyoch_2008,

    It looks like you want to return a string of text from your "display()" function (and then maybe you should call it something besides "display"). For example:

    sub display { my ($self) = @_; if ($self) { my $text = " Student Name: $self->{NAME}\n"; $text .= " Age (yr): $self->{AGE}\n"; $text .= " Regd no: $self->{REGD_NO}\n"; return $text; } else { return "Not found"; } }

    As it is, you're just returning the last thing, which is the value of the print statement (TRUE if successful).

    say  substr+lc crypt(qw $i3 SI$),4,5
Problem sorted out!
by supriyoch_2008 (Scribe) on Apr 06, 2013 at 02:28 UTC

    Hi PerlMonks,

    Please refer to the recent thread "How can one use the print function to get the correct information?" I have already solved the problem myself. Thanks to every Perl Monk who has helped in my endeavour.

      OK, but why do you start a new thread?

      Cheers Rolf

      ( addicted to the Perl Programming Language)

      ... and also, what was your solution so that other monks may benefit from it? (And if you're starting a new thread, a link back to the original thread – which was updated, of course, to reflect the fact that you arrived at a solution! – would be welcome.)

      Why separate thread ?
      Please mark same thread as solved and update solution..

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