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

Hello, Hoping you can help me here.

I'm trying to write a perl script however am I lots of difficulty with a particular sub routine which is essentially grepping a log files, depending on which exist. I'm starting to test with just two log files, but there will be about 8 to select from in the end so hence the usage of subs.

Anyway, I' attempting to check if a 12 Log exists, if it does then assign that scalar to be used later in the loop as the array:

sub GetDecUser {
if (-e $LOGFILE12) {                     
 $LFILE = \@arr12;      # if the 12 log exist, use it         
} else {
 $LFILE = "\@arr10";             
# $LFILE = @arr10;      # Tried this and this just seems to loop throu
+gh the whole log
      
}
print "$LFILE\n";    # this prints @arr10, so the scalar is getting po
+pulated
for $dec ("$LFILE")    # Use what ever log was found in the above if s
+tatement
#for $dec (@arr10)    # this works fine, but its not using the assignm
+ent!
 {
        if ($dec =~ /declared users/)          # match this
        {
         print "TESTING we found it: $dec\n";      # Nothing outputted
+ when I try this. 
        }
 }
}

[download]
Many Thanks (yes I know I can do this easily in shell, but am trying to learn some perl)

Replies are listed 'Best First'.
Re: Assign scalar to array
by cdarke (Prior) on May 18, 2010 at 15:26 UTC
    Your code would be easier to read if you used consistent indentation - honest! It will also help you if you always use strict; and use warnings;
    The use of quotes is part of your problem. The \ is an operator, and \ has no effect inside double quotes. Update: that's rubbish, of course it has an effect, what was I thinking?

    Here is my version, with some variables added to make it work:
    use strict;
use warnings;

sub GetDecUser {

    my $LFILE;
    my $LOGFILE12 = $0;
    my @arr12 = ('The','quick','brown','declared users');
    my @arr10 = qw(The quick brown fox);
    
    if (-e $LOGFILE12) {                     
        $LFILE = \@arr12; # if the 12 log exists, use it         
    } 
    else {
        $LFILE = \@arr10;                 
    }
    
    print "$LFILE\n";    

    for my $dec (@$LFILE)    
    {
        if ($dec =~ /declared users/)          # match this
        {
            print "TESTING we found it: $dec\n";    
        }
    }
}

GetDecUser();

    [download]
[reply]
[d/l]
[select]

      The \ is an operator, and \ has no effect inside double quotes.

      That's not true. It most definitely had an effect (escaped the "@" to prevent interpolation). Just not the desired one.

[reply]

        Dear Monks,

        This is working great now! Many thanks for your patience and assistance

[reply]
Re: Assign scalar to array
by ikegami (Patriarch) on May 18, 2010 at 15:04 UTC
[reply]
[d/l]
[select]

      Thank you for you're reply, but this did not produce any different results

[reply]

        First, start by using use strict; use warnings;. You also have extra quotes in $LFILE = "\@arr10"; use strict; would have caught that. 

        use strict;
use warnings;

my $LOGFILE12 = '...';

sub GetDecUser {
   my $LFILE = -e $LOGFILE12 ? \@arr12 : \@arr10;
   return grep /declared users/, @$LFILE;
}

print "$_\n" for GetDecUser();

        [download]
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[d/l]
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Re: Assign scalar to array
by jwkrahn (Abbot) on May 18, 2010 at 17:02 UTC

    It looks like you should be using a Hash of Arrays or an Array of Arrays instead of twelve separate scalars and twelve separate arrays.

[reply]

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