CODEWITHSUNDEEP
perl
Morad
Morad

Reputation: 2779

How to read the whole file and line by line file in the same Perl script

Whenever I want Perl to read the whole file I put undef $/ before reading the file. I tried to find more information about the variable $/ but without success.

What I need to do is to write a script in Perl that first reads the whole file to a variable and then read another file line by line. How could this be done?

Upvotes: 0

Views: 726

Answers (2)

Carlisle18
Carlisle18

Reputation: 389

Here's another way to do it without directly using $/.

You can use File::Slurp's read_file to read the first file and store its data in memory.

my $text = read_file('filename');
my $bin = read_file('filename' { binmode => ':raw' });
my @lines = read_file('filename');
my $lines = read_file('filename', array_ref => 1);

And, the simplest reading method to read the second file line by line.

open(my $fh, '<', 'input.txt');
while (my $line = <$fh>) {
    ...
}
close $fh;

Upvotes: 2

AntonH
AntonH

Reputation: 6437

You can try opening and reading the first file in a local scope, and then limit the setting of $/ to that scope.

my $firstfile;
{
    open my $fh, '<', $file or die;
    local $/ = undef;
    $firstfile = <$fh>;
    close $fh;
}

# continue with $/ still set

Link:

http://perlmaven.com/slurp (section: localize the change)

Either that, or save the value of $/ to another variable before setting it to undef, and then reset it after reading the first file.

If you don't want to use $/, look into File::Slurp. There is a section on using it in the link I provided.

Upvotes: 2

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