Hello all, I'm trying to parse a config with brackets file on Linux, but I want to remove commented and blank lines from input, before the actual parsing. It is a part of the project, that is written in bash and python and must run on system, that is quite old (RHEL 5, with perl-5.8.8) and limited (no internet connectivity), so I can't use modules and have to "reinvent the wheel".

At the moment I have a code that works, but is wasteful (opening and closing file twice). I first remove unwanted comments and blanks with something like this

 my $data;
open my $FH, '<' , $config or die "Cannot open $config: $!\n";
open my $HF, '>' , $uncommented or die "Cannot open $uncommented: $!\n
+";
$data = <$FH>;
while (<$FH>) {
    next if /^\s*#|^$/;
print $HF "$_";

}
close $FH;
close $HF;

[download]

Or with one liner

 perl -ne 'print unless /^\s*#|^$/' config > uncommented

And then I process the uncommented file 

 my $data;
open my $FH, '<' , $config or die "Cannot open $config: $!\n";
local $/ = undef;
$data = <$FH>;
while ($data =~ m/\{([^}]*)\}/gx ) { 
    print "$1\n";
}
close $FH;

[download]

I'm not able to do both on one file opening. Either regex doesn't match anything, or comments and blanks are not stripped before parsing

I understand, that the problem lies in input record separator "$/", which must be set to undef for multiline pattern match, but for per line match it must be newline (removing comments and blanks)

I wonder, if there is any elegant way how to sequentially use both while opening file only once

Thank you in advance for any tips

Yakup

In reply to Match pattern per line and after another one as multiline in single file opening by Yakup

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