Passing value outside of loop

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

I am trying to pass a parameter outside of my loop but it says I can not do this.

use strict;
my $mydir = "/path/paths";
my $bool = 0;
opendir(DIR, $mydir) || die "Can not open $mydir: $!\n";
while (my $file = readdir(DIR))
{
   if($file =~ /^myname\.doc$/i)
   {

         $bool = 1;
       
   }
}
closedir(DIR);

if($bool)
{
print "$file"; 
}
[download]

My error message:

Global symbol "$file" requires explicit package name at C:\Perl\bin\sc
+rp.pl line
 22.
Execution of C:\Perl\bin\scrp.pl aborted due to compilation errors.
[download]

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Re: Passing value outside of loop by davorg (Chancellor) on Jan 07, 2003 at 16:32 UTC
You create a lexical variable called $file that exists within the scope of your while loop. Once the while loop terminates, that scope disappears and the that variable ceases to exist. You then try to access another variable called $file. As there is no lexical variable of that name in existance, Perl assumes that it is a package variable. But as you have "use strict" turned on, you need to either predeclare or explicitly name any package variables that you use. As you have done neither of these two things, you get the error you've shown us. The solution to your problem would be to create the lexical variable $file outside of the loop, so that it doesn't just exist within that scope. -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]
Re: Passing value outside of loop by hardburn (Abbot) on Jan 07, 2003 at 16:33 UTC
my() creates a variable in the current lexical scope. Since the "my $file" is in the while loop's condition, $file is created in the while loop and then goes away. Try this: `my $file; while($file = readdir(DIR)) { ...` [download] Also, unless you have a bunch of other code in the while loop that needs to run, you should exit the loop once $bool becomes true (BTW--$bool is a really lousy name for a variable). Additionally, it is usually good practice in a regex match to use '^' and '$' to indicate line beginnings/ends, and '\A' and '\z' to indicate string beginnings/ends. This is not a strict requirement, and you'll usually be OK if you switch them around. `my $file; while ($file = readdir(DIR)) { if($file =~ /\Amyname\.doc\z/i) { $bool = 1; last; } }` [download]	[reply] [d/l] [select]
Re: Passing value outside of loop by FamousLongAgo (Friar) on Jan 07, 2003 at 16:36 UTC
You're declaring the variable within the lexical scope of the `while` block, so it goes out of scope by the time you reach the conditional. Try this instead: `my $found; while ( my $file = readdir(DIR) ){ $found = $file, last if $file=~/^myname\.doc$/i; } closedir(DIR); print "Found: $found" if $found;` [download]	[reply] [d/l] [select]
Re: Re: Passing value outside of loop by Anonymous Monk on Jan 07, 2003 at 17:52 UTC
Thank you to all.	[reply]
Re: Passing value outside of loop by thewalledcity (Friar) on Jan 07, 2003 at 16:36 UTC
I believe that your variable $file is only available inside the while loop because of scope (someone feel free to correct me if I'm mistaken). You should put the `my $file` before the start of the while loop.	[reply] [d/l]
Re: Passing value outside of loop by Arien (Pilgrim) on Jan 08, 2003 at 08:04 UTC
That's a lot of code just to see if there's a file `$file` in `$dir`. Use Perl's file tests: `my $dir = "/path/paths"; my $file = "myname.doc"; print "Found '$dir/$file'.\n" if -f "$dir/$file";` [download] — Arien	[reply] [d/l]