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

open (my $rfh,'<', $entry) or die "cannot open > $entry: $!";
open(my $new, '>', "$name\_new.txt") or die "cannot open: $!";
my @data = <$rfh>;

foreach my $l (@data) {
if ($l =~ m/$signal2\(\d+\).*\s*<=\s*$signal1\(\d+\).*/){
my $i;
for($i=0;$i<7;$i++){
my $j = $i + 1;
print $new "$signal2\_rrfa_$label($j) <= $signal1\_rrfa_$label($i);\n"
+;
}
$required_line = $&;
}
else{
print $new $l; 
}
}
close($new);
close($rfh2);

[download]

My new file does not contain the lines from the original file when the if condition fails ( I mean the else part is not executed). The new file has only lines when if conditioned passed.

Replies are listed 'Best First'.
Re: Filehandle problem
by Random_Walk (Prior) on May 07, 2013 at 11:18 UTC

    What is the variable $required_line for? What are in $signal[1|2] My guess is that this is a fragment of a larger script. Can you give an example of some input lines as well please?

    Why are you using $1 as the variable to write? What do you think happens to this variable during pattern match failure?

    Cheers,
    R.

    Pereant, qui ante nos nostra dixerunt!
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[d/l]
[select]

      Hi, I am storing the value whatever is matched in the if condition in the $required_line variable. The data file is too large of 40k lines.

[reply]

        Just a couple of lines of the input demonstrating a match and a fail would help. Try replacing the use of $1 with something other than a special variable, I typically use $line. Then see how you get on.

        Cheers,
        R.

        Pereant, qui ante nos nostra dixerunt!
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[d/l]
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Re: Filehandle problem
by jnyman (Acolyte) on May 07, 2013 at 11:43 UTC
    Are you sure you are not trying to read the new file before the file handle has been closed? (and autoflush $| has not been set for $new)
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Re: Filehandle problem
by graff (Chancellor) on May 07, 2013 at 23:22 UTC
    After I applied appropriate indentation on the OP code (so I could read it), I noticed something odd about your print statement: 
    print $new $l;

    [download]
    Normally, the 'print' function takes a list, which means that there should be commas between its args. I didn't have your data files on hand, so I did a couple quick one-liner experiments: 
    perl -le '$x="foo"; $y="bar"; print $x $y'

perl -le '$x="foo"; $y="bar"; print $x, $y'

    [download]
    The first of those (without a comma) didn't print anything at all. The second one printed "foobar", as expected.

    In the first try, without the comma, the 'print' function is trying to interpret $x as a file handle, and failing. In the absence of use warnings;' there wasn't even a hint about the problem, but a third experiment was more instructive: 

    perl -wle '$x="foo"; $y="bar"; print $x $y'
print() on unopened filehandle foo at -e line 1.

    [download]
    Given that sort of condition, the default (prudent) behavior is for the print function to do nothing at all.

    Sorry - total brain fart on on the stuff above. I forgot that $new was supposed to be a file handle. Oh well.

    UPDATE: Random Walk has apparently solved your problem, but here's a slightly different version of the same solution anyway... (possibly a bit less different from the OP code, possibly a little simpler, and, well, at least this allows my reply to have some usable content): 

    use strict;
use warnings;

my $name = "name";

# open( my $rfh,'<', $entry ) or die "cannot open > $entry: $!";
open( my $new, '>', "$name\_new.txt" ) or die "cannot open: $!";

my $signal1 = "s_abc_out";
my $signal2 = "s_abc_in";
my $label = "label";

while ( <DATA> ) {  # would be <$rfh> for you
    if ( /$signal2\(\d+\).*\s*<=\s*$signal1\(\d+\).*/ ) {
        for my $i ( 0 .. 6 ) {
            my $j = $i + 1;
            print $new "$signal2\_rrfa_$label($j) <= $signal1\_rrfa_$l
+abel($i);\n";
        }
    }
    else{
        print $new $_; 
    }
}

__DATA__
.................................
s_abc_in(1450) <= s_abc_out(324);
s_abc_in(1451 <= s_abc_out(1450);
.................................

    [download]
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[d/l]
[select]
      That was not the solution. If you test the original code with some debug values on the variables, the lower branch is writing to the file as supposed.
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