Re: Nested While loop not working

Welcome to the monastery.

I created two files:

$ cat ABC
qwe
asd
zxc

$ cat CDE
rty
fgh
vbn
[download]

I ran your code like this (apart from the shebang and three use lines, it's a copy of what you posted):

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

open(file_one,"ABC");
while(my $line = <file_one>)
 { open(file_two,"CDE");
     while(my $line2=<file_two>)
      { print "line : $line  line2 : $line2 \n";
      }
   close(file_two);
}
[download]

I got a warning but then output from both files, like this:

Name "main::file_one" used only once: possible typo at ./pm_example.pl
+ line 8.
line : qwe
  line2 : rty
 
line : qwe
  line2 : fgh
 
line : qwe
  line2 : vbn
 
line : asd
  line2 : rty
 
line : asd
  line2 : fgh
 
line : asd
  line2 : vbn
 
line : zxc
  line2 : rty
 
line : zxc
  line2 : fgh
 
line : zxc
  line2 : vbn
[download]

So, check the filenames, file permissions and file contents. If you ask for diagnostic messages, you'll usually get useful information: see Pragmas for documentation on those that I used; while you're learning, diagnostics can also be useful but don't leave it in production code.

Here's a better way to write it:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

open my $fh1, '<', 'ABC';
while (defined(my $line1 = <$fh1>)) {
    chomp $line1;
    open my $fh2, '<', 'CDE';
    while (defined(my $line2 = <$fh2>)) {
        chomp $line2;
        print "line1 : $line1  line2 : $line2\n";
    } 
}
[download]

Now the output has no warnings and all those extra newlines are gone:

line1 : qwe  line2 : rty
line1 : qwe  line2 : fgh
line1 : qwe  line2 : vbn
line1 : asd  line2 : rty
line1 : asd  line2 : fgh
line1 : asd  line2 : vbn
line1 : zxc  line2 : rty
line1 : zxc  line2 : fgh
line1 : zxc  line2 : vbn
[download]

See the following for information on what I did differently to your posted code: chomp; defined; and open. Also, the following have useful information regarding while loops: "perlsyn: Loop Control" and "perlop: I/O Operators". Finally, if you've only just started to learn Perl, I recommend you first read all of "perlintro -- a brief introduction and overview of Perl".

-- Ken

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Re^2: Nested While loop not working by Manisha (Initiate) on Mar 11, 2014 at 10:33 UTC
Hi Vinoth and Ken, Actually my requirement is there are two files `F1,F2 F1 has data NAMES name1 name2 ADDRESS street1 street2 PHONE num1 is num2 is F2 has data name1 sirname1 street1 housenumber 1 num1 is 8784794 num2 is 9888948 street2 housenumber23 name2 sirname2` [download] so i read each line in F1 and see if its mandatory(ends with (*) then under that heading i take the values and its corressponding complete value is taken from F2 so finally what i should get is `NAMES name1 sirname1 NAMES name2 sirname2 PHONE num1 is 8784794 PHONE num2 is 9888948` [download] Thanks , my code is `#! usr/bin/perl use strict; use warnings; my $line; my $str; use diagnostics; open my $file_one,'<','F1' or die "unable to open"; while(defined($line=<$file_one>)) { chomp($line); if ($line =~m/(\\*)/) { $str = $line ; # print " $str \n"; } else { open my $file2,'<','F2' or die "unable to open "; while(defined(my $line2=<$file2>)) { if($line2=~m/$line/) { print " line : $str line2: $line2\n"; } } close($file2); } }` [download] its giving error Invalid [] range "=-," in regex; marked by <-- HERE in m/ 144 x Lc +b (P CAL_LCBMS [CAL_LCBMS] T lcb I [ACT=-, <-- HERE NCLK=chpl::ec0+clk, FORCE_T=-, SG=chpl::ec0+sg+region1+no_l +cc+plat_flush_nto1, THOLD_B=chpl::ec0+sl_thold+ab st+region1+no_lcc, MPW1_B=-, MPW2_B=-, DLY_LCKR=-, DLY0=chpl::ec0+time ++region1+no_lcc+slat, DLY1=chpl::ec0+time+region1 +no_lcc+slat, PW0=chpl::ec0+time+region1+no_lcc+slat, PW1=chpl::ec0+ti +me+region1+no_lcc+slat, PW2=chpl::ec0+time+region 1+no_lcc+slat] E [SG=OR(chpl::ec0+lbist_ary at ./stest line 21, <$file +2> line 1. at ./stest line 21 [download] where line 21 is the pattern matching statement if($line2=~m/$line/)	[reply] [d/l] [select]
Re^3: Nested While loop not working by kcott (Archbishop) on Mar 12, 2014 at 06:49 UTC
Firstly, please put your error output in `<code>...</code>` tags. Does what you've posted there look the same as the error message you received? When posting, before hitting the `[ create ]` button, keep editing then hitting the `[ preview ]` button until your post accurately reflects the information you're attempting to communicate. When updating a post, there's no `[ preview ]` button; you need to keep editing then hitting the `[ update ]` button. The input data you described looks nothing like what you're reading. Did you open the correct file? The data you've read into `$line` starts off something like (my best guess at reconstructing it): `144 x Lcb (P CAL_LCBMS [CAL_LCBMS] T lcb I [ACT=-, NCLK=chpl::ec0+clk +, ...` [download] That (along with all the text that follows it) contains many characters that have special meanings within a regex. A character class is specified within square brackets (i.e. `[...]`). The "`[ACT=-,`" part of `$line` starts a character class which includes all the charcters in the range "`=-,`"; however, `ord('=') == 61` and `ord(',') == 44`, so the start of that range is after its end and, therefore, invalid. That explains the error which would have looked something like: `Invalid [] range "=-," in regex; marked by <-- HERE in m/ 144 x Lcb (P CAL_LCBMS [CAL_LCBMS] T lcb I [ACT=-, <-- HERE ...` [download] While I suspect this is a mistake on your part (e.g. you're reading the wrong file), if you want to interpolate data like that into a regex, you'll need to do something like: `/\Q$line/` [download] See quotemeta for details. -- Ken	[reply] [d/l] [select]
Re^4: Nested While loop not working by Anonymous Monk on Mar 12, 2014 at 09:34 UTC
Thank you so much Ken :) it did help	[reply]
Re^4: Nested While loop not working by Manisha (Initiate) on Mar 12, 2014 at 09:37 UTC
Thank you so much Ken :) it did help and Sorry for the wrong format of text	[reply]