How to replace ^M character in perl code in same file - perl

Question

I am looking to delete control-M character file in perl code (not perl one liner).
I tried this, but it will write to new file. Whats the way to do it in same file?
#!/usr/bin/perl
open (IN, '<', "FILE.dat") or die "$!";
open (OUT, '>', "FILE.dat.cpy") or die "$!";
while(<IN>)
{
$line = $_;
$line=~ tr/\015//d;
print OUT "$line";
}
close (IN);
close (OUT);

Answer 1

store the file internal in a String.
#!/usr/bin/perl
my $content = ''
open (IN, '<', "FILE.dat") or die "$!";
while(<IN>)
{
$line = $_;
$line=~ tr/\015//d;
$content .$line
}
close (IN);
open (OUT, '>', "FILE.dat") or die "$!";
print OUT $line;
close (OUT);

Answer 2

It could be done using $^I variable.
use autodie;
local $^I = "";
local #ARGV = "FILE.dat";
while (my $line = <>) {
$line=~ tr/\r//d;
print $line;
}
From perlvar
$^I - The current value of the inplace-edit extension. Use undef to disable inplace editing.
So it is undef by default, empty string is used to edit in-place, and non-empty string will be added as suffix to backup file name.

Answer 3

You needn't be afraid of coping the edited content to a new file, and then renaming. This is the standard way to edit content unless you're dealing with a file with fixed with records.
Check out How do I change, delete, or insert a line in a file, or append to the beginning of a file? to observe most of the ways to edit content, and the majority of them will ultimately be copying to a new file.
My preferred advice is to use in-place edit as demonstrated by mpapec. The only addition is that Windows forces you to specify a backup, so just need to add the unlink line after the processing.
use strict;
use warnings;
use autodie;
my $file = 'FILE.dat';
local #ARGV = $file;
local $^I = '.bak';
while (<>) {
tr/\r//d;
print;
}
unlink "$file$^I";
If you insist on being able to open the file only once, then perhaps you can take a look at I still don't get locking. I just want to increment the number in the file. How can I do this?
use strict;
use warnings;
use autodie;
use Fcntl qw(:seek);
my $file = 'afile.dat';
open my $fh, '+<:raw', $file;
my $data = do {local $/; <$fh>};
seek $fh, SEEK_SET, 0;
truncate $fh, 0;
$data =~ tr/\r//d;
print $fh $data;
close $fh;