[Perl] append to new file

noir911 · 02-08-2007, 04:04 AM

I can print the output of a file to STDOUT but I want to append it to a new file. Here's my code

Code:

#!/usr/bin/perl -w
my $file="file.log";
my $nf="nf.log";
open (FILE, "$file") or die ("can't open this: $!");
my @lines=<FILE>; 
print @lines;
close (FILE) or die "FILE can't be closed: $!";

noir911 · 02-08-2007, 04:15 AM

Not sure if it's "efficient" but I found this script [1] which helped me to solve this issue. Here's the new solved code

Code:

#!/usr/bin/perl -w

my $file="file.log";
my $nf="nf.log";

open (FILE, "$file") or die ("can't open this: $!");

 my @lines=<FILE>;

close (FILE) or die "FILE can't be closed: $!";
open (NF, ">> $nf");
foreach $line (@lines) {
print NF $line;
}
close NF;
exit;

[1] http://www.linuxquestions.org/questi...ad.php?t=54267

druuna · 02-08-2007, 04:20 AM

Hi,

To write/append to a file you need to open another filehandle (for $nf in your case).

Something like this:

open NEWFILE, ">$nf" or die "Can't open $nf";

To write to this filehandle:

print NEWFILE @lines;

You also need to close it again (close NEWFILE; ).

To append to an already existing file, use >> instead of >.

Your example code would look like this:

Code:

#!/usr/bin/perl -w
my $file="file.log";
my $nf="nf.log";
open NEWFILE, ">$nf" or die "Can't open $nf";
open (FILE, "$file") or die ("can't open this: $!");
my @lines=<FILE>; 
print NEWFILE @lines;
close (FILE) or die "FILE can't be closed: $!";
close NEWFILE;

Hope this helps.

noir911 · 02-08-2007, 04:36 AM

Thanks. It's neat and small - only 9 lines!

kshkid · 02-08-2007, 06:29 AM

Code:

close (FILE) or die "FILE can't be closed: $!";
close NEWFILE;

I have few considerations with the above!

Say if the filehandler FILE is not closed properly, necessarily NEWFILE handler also will not be closed which I think can be avoided.

druuna · 02-08-2007, 06:38 AM

Hi,

I never use the 'or die' part in the close statement, but the OP does/did.

You are correct by stating that if close FILE fails, the close NEWFILE is never reached. But if the script stops, the file is (probably) closed anyway. I say probably, cause I've never actually had this problem myself.

All in all you are correct in warning the OP (and others), and a better way would be:

Code:

close FILE;
close NEWFILE;