Reading a File into a Variable in Perl

For large files, consider File::Slurp. It’s faster than the conventional approaches:

# Slurp the whole file
{
  local $/ = undef;
  open my $fh, '<', 'myfile' or die "Couldn't open file: $!";
  binmode $fh;
  my $string = <$fh>;
  close $fh;
}

Without binmode:

{
  local $/ = undef;
  open my $fh, '<', 'myfile' or die "Couldn't open file: $!";
  my $string = <$fh>;
  close $fh;
}

Join the lines:

open my $fh, '<', 'myfile' or die "Couldn't open file: $!";
my $string = join('', <$fh>);
close $fh;

Append in a loop:

open my $fh, '<', 'myfile' or die "Couldn't open file: $!";
my $string;
while (<$fh>) {
  $string .= $_;
}
close $fh;

Read a fixed number of bytes:

open my $fh, '<', 'sample.txt' or die "Error: $!\n";
read($fh, my $data, 2000);
close $fh;

The read function takes a filehandle, a destination variable, and the number of bytes to read. The example above reads 2000 bytes into $data.

Using sysread:

my $file = 'sample.txt';
{
  local *FH;
  open FH, '<', $file or die $!;
  sysread FH, my $content, -s $file;
  close FH;
}