Perl: open file but not overwrite existing one but append number - perl

Question

I wonder if any module exist that can automate file numbering process.
If i try open "foo.bar" and it exists i open "foo_1.bar" without race condition.
What if two apps try open some file. Open fail or they get filehandles with diferent number?
Very thx for help.

Answer 1

I don't know of a canned module to do this off the top of my head, but the basic idea if you want a sequential file name is:
use Fcntl;
use Errno;
$seq = "";
until (defined ($fh = sysopen("foo".$seq.".bar", O_WRONLY|O_CREAT|O_EXCL, 0600))) {
last if $! != EEXIST;
$seq eq '' && $seq = '_0';
$seq =~ s/(\d+)/$1 + 1/e;
}
# if !defined $fh then $! contains the error, otherwise "foo".$seq.".bar" is created

Answer 2

Opens unique file name for writing. Return array ref to IO::File ref and writing name.
If fail return undef. Work with warnings and strict.
use Fcntl;
use Errno;
use IO::File;
sub open_unique {
my $file = shift || '';
unless ($file =~ /^(.*?)(\.[^\.]+)$/) {
print "Bad file name: '$file'\n";
return;
}
my $io;
my $seq = '';
my $base = $1;
my $ext = $2;
until (defined ($io = IO::File->new($base.$seq.$ext
,O_WRONLY|O_CREAT|O_EXCL))) {
last unless $!{EEXIST};
$seq = '_0' if $seq eq '';
$seq =~ s/(\d+)/$1 + 1/e;
}
return [$io,$base.$seq.$ext] if defined $io;
}

Answer 3

You might want to look at File::Temp.
Something like:
($fh, $filename) = tempfile('foo_XXXX', SUFFIX => '.bar');
print $fh "Some data\n";
close($fh) or die;