Shell Programming and Scripting

Thanks, but i really cant believe a perl one liner exists to do this, but the only way to do this omside an actual perl script is to run system() to run sed, then run system() again to run cp to copy the file back over


surely ?

You can write something like this (untested).
Backup your files first!

Code:

#! /usr/bin/env perl

use warnings;
use strict;

my @files   = glob '/tmp/*'; # adjust the glob!
my $logfile = $0 . '.log';

open LH, '>', $logfile or die "open $logfile: $!\n";

for (@files) {
    {
        local ( $^I, @ARGV ) = ( '', $_ );
        while (<>) {
            print LH $ARGV, ": record ", $., "\n" and next if /^\s*$/;
            print;
        }
    }
}

close LH or warn "close $logfile: $!\n";

That's not a good enough reason.
You do not have to
(1) open
(2) read and
(3) close a file

just to find out which line number is blank. Sure, you can, but you don't have to.
If you do, then it's a convoluted way of doing things. The sed program didn't open, read, and close the file (at least explicitly).

Send the blank line to a log file ? This wasn't the requirement in your original post.

Not sure I understand this. If there is no need to fix it, then why do you even want to do it ?
As for the possibility, you opened the file for reading (the default). And you wanted to write to a file. They are not the same thing.

Of course it doesn't, if you understand what you are trying to do. "$file" is just a variable, not an actual file. And the "s///" operator simply works on the value of that variable. Your variable did not have a newline character at the beginning, so it wasn't removed. If it had, then it would've been removed -

Code:

$ 
$ perl -le '$file = "
/var/tmp/0629AN1208.net"; print "Before: $file"; $file =~ s/^\n//g; print "After : $file"'
Before: 
/var/tmp/0629AN1208.net
After : /var/tmp/0629AN1208.net
$ 
$

Perl is simply doing what it was told to do.
And if you are thinking that the "s///" operator will actually open a file and remove newlines, just because the variable was called "$file", then you need to brush up on the basics first.

That one-liner writes to the file because of that qualifier "-i". Check the perl documentation. You could make it work on a hierarchy of files, but the solution would be more verbose than that sed solution.

tyler_durden

Here is what you can do:

1. A seperate script using sed to remove the blank lines
2. Call sed from within your perl script with system
3. The perl -i route in the above post
4. Dump each line of the file to an array except blank lines, open the files again for writing, and clobber them with the contents of the array
5. Create a new file, open it for writing, add an else to the if ( /^$/ ) that counts blank lines, and print the non blanks to the new file. Then overwrite the original with the new one.

1,2, and 3 are much easier than 4 or 5.

thank you for your responses, I have been learning perl for the grand total of 5 weeks now...so go easy on me

i will look at using the sed solution instead

thanks again