Chomp doesn't seem to work

JaredHess has asked for the wisdom of the Perl Monks concerning the following question:

My Perl and programmer newbie-ness keep me foul-fettered in the dungeons of code damnation! There is no release for my wretched soul! Alas! Perhaps the merciful monks can release me?

I can't figure out newlines between Windows and Unix platforms! Ahhhrgg! What a mess!

Here's the deal. Our web server is running Apache on a Unix system and my local machine is Windows XP Pro. I have a datafile of email addresses that I'm reading from on our web server. This list gets dynamically created from another script, pulling emails from our MYSQL database and putting them in the text file, one email per line.

I can create the list fine and I can read from it just fine in my current script. The only problem I run into is when I try to modify the list manually (maybe removing a few lines of emails) and then reuploading it to the server. That is when I become fettered. And there's a lot of wailing and gnashing of teeth because the darn chomp() function doesn't seem to work on my Windows modified .txt file. Then the rest of my script doesn't work.

I've created a crude workaround using the chop() function instead that has given my fevered brow at least some relief.

    $lastchar = substr($email,-1);
    print p,$lastchar;

    if ($lastchar =~ /[a-zA-Z]/){
    } else {
    print p, "Testing...Last char is not alphabetic";
    chop($email);
    print p,"Testing...found newline, so we're chopping it!";
    print p,"Testing...$email after chop " . length($email);
    }
[download]

But isn't there an easier way to set chomp to work with either Windows or Unix newlines? I don't know. I have searched the Good Book (Programming Perl) but could not find the answers.

Comment on Chomp doesn't seem to work Download Code

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Re: Chomp doesn't seem to work by Ovid (Cardinal) on Feb 03, 2005 at 00:59 UTC
Er, I can never remember the darned line endings, but I'd try something like: `{ local $/ = "\n"; chomp $email; }` [download] `$/` is the input record separator. That's what chomp really removes. By using local in the brackets, you can temporarily reset that to whatever you need to chomp on. After you leave the brackets, `$/` will have its previous value restored. (I think it's "\n" for Unix, but I can't recall.) Oh, wait. It's a Windows file uploaded to Unix that's the problem? Then I think the line ending might be "\r\n". I never keep those straight. And for the record, the problem is because Unix and Windows use different line endings and chomp defaults to the line ending of the OS you currently are on. Cheers, Ovid New address of my CGI Course.	[reply] [d/l]
Re: Chomp doesn't seem to work by dave_the_m (Monsignor) on Feb 03, 2005 at 01:07 UTC
if you have a file with indeterminate line-ending chars, I'd recommend `$line =~ s/[\r\n]+$//;` [download] Dave.	[reply] [d/l]
Re^2: Chomp doesn't seem to work by halley (Prior) on Feb 03, 2005 at 15:45 UTC
Is there any reason you happened to anchor your regex with an "end-of-line" `$` code? Because that will depend on the definition of a "line" too. If I'm stripping a single line thing, I'd use `\z` to anchor to the end of the string. Similarly, the \n and \r are semantic, referring to this platform's idea of newlines and returns. Specify exact encodings that you're encountering. For sources using ASCII or UTF-8, that's probably `\x0A` and `\x0D`. `$text =~ s/[\x0D\x0A]+\z//;` [download] -- `[ e d @ h a l l e y . c c ]`	[reply] [d/l] [select]
Re: Chomp doesn't seem to work by sh1tn (Priest) on Feb 03, 2005 at 01:08 UTC
Hi, `# some ugly way to get rid of new line char(s) $email =~ s/\r?\n//g; # or maybe more practical push @email, $_ for split /\r?\n/, $email # and later for(@email){ # we have each line as an array element }` [download]	[reply] [d/l]
Re: Chomp doesn't seem to work by demerphq (Chancellor) on Feb 03, 2005 at 09:07 UTC
If you upload your file to the server via FTP then it will automatically convert the line endings on transfer (assuming you dont use binary mode transfer). Or you can use an editor that can handle unix line endings in the first place. www.ultraedit.com is one such editor (and my preference). Lastly you could use dos2unix from any one of many sources such as www.cygwin.com. While making your code resilient to this kind of problem is one solution, IMO the better solution is to just avoid the problem in the first place. If you are going to use files from hetergeneous architectures then decide on a format that you will use on all of them and stick to it. --- demerphq	[reply]
Re: Chomp doesn't seem to work by Random_Walk (Prior) on Feb 03, 2005 at 12:26 UTC
you may find some useful hints about the various representaions of line endings at this recent node 427108 Cheers, R. Pereant, qui ante nos nostra dixerunt!	[reply]
Re: Chomp doesn't seem to work by Anonymous Monk on Feb 03, 2005 at 22:48 UTC
assuming you are reading in input line by line, maybe it would be easier just to clean the line to make sure it's in the right format. Like `chomp(my $line = <FILE>); $line =~ tr/\r//d;` [download]	[reply] [d/l]