search and replace pattern inside file not working as expected

matze77 has asked for the wisdom of the Perl Monks concerning the following question:

#!/usr/bin/perl
use strict;
use warnings;
my $alter = "3";
#assign a value to alter different than 0 or 1 which is used later ...
my $openfile = "$ENV{SystemRoot}/win.ini";
{
open (MYFILE, ">>$openfile")or die "Can't open file 1: $!\n"; #open fo
+r write, append not read!
open (TEST, "c:/windows/win.ini") or die "Cant open file $!\n";

while(<TEST>) {
    if ( $_ =~ /[ARTEC]/ )  {
        my $alter = 1;
    } else {
    my $alter = 0;
    }
  } 
}  
  if ($alter == 1) {
      #do something; 
      print "..";   
     }
 
close(MYFILE);
close(TEST);
[download]

snippet of win.ini

blabla
[ARTEC]
IniFile=f:\vaa\basis\vaa01.ini
bla
[download]

It seems like the while block never gets executed, any help?
Thx in Advance
MH

Update, Changed it now works:
not using my to declare variables ...

use vars qw($change $alter);
$alter = 0;

sub readfile { while(<TEST>) {
    if ( $_ =~ /^\[ARTEC\]$/ )  {
               $alter = 1;
    exit print "found it exiting no need to change something";
          
        }else {
        $change = 1;
        print "n ";
        }        
    }
  return;
  } 
}
if ($alter == 0 and $change == 1) {
       #do something ...
       print "changed\n";   
      
    }
[download]

Comment on search and replace pattern inside file not working as expected Select or Download Code

Replies are listed 'Best First'.
Re: search and replace pattern inside file not working as expected by Corion (Patriarch) on Jan 04, 2010 at 15:54 UTC
How did you determine that your `while` loop never gets executed? Also, `/[ARTEC]/` likely does not match what you expect it to match, given your input file. See perlre about character classes. Most likely, you wanted `/^\[ARTEC\]$/`.	[reply] [d/l] [select]
Re^2: search and replace pattern inside file not working as expected by matze77 (Friar) on Jan 04, 2010 at 16:19 UTC
Yes. You are right. It would match any, but not the "string" of the uppercases "ARTEC" which is not what i wanted. I "tested" it by putting print statements into the loops now. It works with the new pattern. But i made another mistake the variable needs to be assigned "globally" outside the while loop or my next if block never gets executed. Any hint? ... How could i declare the variable to work outside the loop my and local wont do ...? Thanks MH	[reply]
Re: search and replace pattern inside file not working as expected by toolic (Bishop) on Jan 04, 2010 at 15:59 UTC
It looks like a variable scoping issue. You set `$alter` to 3 outside your while loop. Inside your while loop, you declare another variable, also named `$alter`, which is different from the `$alter` outside your while loop. Then you check `$alter` after your while loop. Since it is still 3, `if ($alter == 1)` evaluates to false. You can prove this to yourself with more liberal usage of print (tip #2 from the Basic debugging checklist), such as inside your while loop. In the future, receiving help would be much more efficient if you provide a smaller code example which is completely self-contained (not relying on external files). Using perltidy before posting would also make your code clearer. Update: not using my to declare variables ... You can replace: `use vars qw($change $alter);` [download] with: `my ($change, $alter);` [download] Further reading in the Tutiroals section: Variables and Scoping	[reply] [d/l] [select]