Re^2: removing the need for tmp files from script

[novice2015]

Fantastic information. I was wondering though, you don't seem to be able to use the "filehandle" variable like a real file in a script. For example: I have this beginnerish script

open my $fh2, '<', '/tmp/mlist.txt' or die "unable to open file '$file
+' for reading : $!";
open my $fh9, '>', '/tmp/listk.txt' or die "unable to open file '$file
+' for reading : $!";
while (<$fh2>) {
   my @fields = split(',', $_);
 local $" = ',';
       if ($fields[2] eq '1' || $fields[2] eq '0') {
             print $fh9 "@fields[4]\n" if /MONTHLY/ && !/,-,/;
             }
           }
           close $fh2;
           close $fh9;

This is clumsy but it works. However, if I try to use the variable assigned to a filehandle in the same way:

open my $bpfh1, '<', \$forbpjoutput or die $!;
  while (<$bpfh1>) {
my @fields = split(',', $_);
my $fields;
 local $" = ',';

       if ($fields[2] eq '1' ||$fields[2] eq '0') {
             print "THESE ARE THE>>> $fields[4]\n" if /MONTHLY/ && !/,
+-,/;
        
close $bpfh1;
             }
          }

it does work but what happens is that it never stops printing the "file" or the fields4 It continues until out of memory. Is there a way to do this differently? This is probably a very basic question, but I don't have much experience with filehandles which are variables.

[Cristoforo]

Hi novice2015

The link to open that BillKSmith mentioned in his post has the following text.

# in-memory files
21. open(my $memory, ">", \$var)
22.     or die "Can't open memory file: $!";
23. print $memory "foo!\n";              # output will appear in $var

This shows how to write to an in-memory file.

To read from an in memory file, you would do this:

#!/usr/bin/perl
use strict;
use warnings;

my $file = 'here
are
some
words
I
want
';

open my $fh, '<', \$file;

chomp(my @words = <$fh>);

my $pattern = join "|", @words;

print $pattern;

That would be a way to not need the tmp. file.

[novice2015]

this works great. However, I have one issue in that the file has 2 lines in it and only the first line gets printed.

 
my $pattern = join '|', @words;
my $forx;
open my $bpfh1, '>', \$forx or die $!;
        for (@bpj) {
        print $bpfh1 "$_\n", $_ if /$pattern/;
}


open my $bpfh1, '<', \$forx or die $!;
  while (<$bpfh1>) {
my @fields = split(',', $_);
my $fields;
 local $" = ',';

       if ($fields[2] eq '1' ||$fields[2] eq '0') {
             print "THESE ARE THE>>$fields[4]\n" if /MONTHLY/ && !/,-,
+/;
}
        
close $bpfh1;
          }
close $bpfh1;
}

So what I get is LISTING-INVENTORY-CATALOG LISTING-PURCHASING-CATALOG The variable (memory file) $forx does contain data, and it prints out just fine. But only the first line. I have tried different things to make the second line print, such as closing the file earlier, but it doesn't work. I've had this problem before but can't remember how I got it resolved. Any ideas?

[BillKSmith]

I cannot duplicate your problem. When I run your code on my system (perl v5.20.2 on Windows 10), it terminates with no error messages and no output. It I use warnings, I get several copies of a warning about uninitialized value in $bpfh1. If I declare $forbpjoutput as a lexical variable and define it as a null string, I get no messages and no output even using strict and warnings. (This is exactly what I expect).

use strict;
use warnings;
my $forbpjoutput = q();
open my $bpfh1, '<', \$forbpjoutput or die $!;
... # Exactly as in your post.

As Cristoforo pointed out, you probably did not intend to input from a null file. I cannot guess what you really did intend to do.