If like me you are unfortunate enough to live in an area not covered by *any* form of broadband access and must use a modem this script may help if you need to know your latest dynamically assigned IP. I've configured a NAT/Firewall server and need to let several people know the latest IP so they can log in. The $to address is assigned to a mailist but YMMV. Any comments welcome.
#!/usr/bin/perl -w
use strict;

my $from = "foo\@bar.com";
my $to = "bar\@foo.com";
my $subject = "Latest IP address";

my @ifc = `/sbin/ifconfig ppp0`;
chomp ($_ = $ifc[1]);
/inet\ addr:(\d+\.\d+\.\d+\.\d+)\s+.*$/;

open (MAIL, "|/usr/lib/sendmail -oi -t -odq") || die "Can't fork for s
+endmail: $!\n";
print MAIL "From: $from\nTo: $to\nSubject: $subject\n\n";
print MAIL $1;
close (MAIL);

[download]

Replies are listed 'Best First'.
•Don't use $1 without testing! (was Re: Getting the latest IP after dial-up)
by merlyn (Sage) on Aug 25, 2002 at 16:22 UTC 
    /inet\ addr:(\d+\.\d+\.\d+\.\d+)\s+.*$/;
...
print MAIL $1;

    [download]
    I'd fail this in a code review. You've not assured a match on the regex, so the $1 there could be the previous $1, since the dollar vars are not updated on an unsuccessful match.

    At the very minimum, put "or die" after the match.

    -- Randal L. Schwartz, Perl hacker

[reply]
[d/l]
      Thanks merlyn, the comments are valid and welcome. I'm rewriting the code with a filehandle to check and collect the old IP and only send a mail if different... I have much to learn.
[reply]
Re: Getting the latest IP after dial-up
by Mr. Muskrat (Canon) on Aug 25, 2002 at 17:00 UTC

    How do I find out my hostname/domainname/IP address?

    How do I send mail? Well, I would have linked to perlfaq9 again for that except that it mentions using Mail::Mailer (which I could not even find using ppm3) or Net::SMTP (which I have only had limited success with on Windows). So I'm going to use Mail::Sendmail. After you have installed it, you should edit Mail::Sendmail.pm and change the line to show your actual SMTP server:
        'smtp'    => [ qw( localhost ) ],

    Combine everything together and what do we get?

    #!/usr/bin/perl -w
use strict;
use Socket;
use Sys::Hostname;
use Mail::Sendmail;
my $from = "foo\@bar.com";
my $to = "bar\@foo.com";
my $subject = "Latest IP address";
my $host = hostname();
my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost'));
my %mail = (To      => $to,
            From    => $from,
            Subject => $subject,
            Message => $addr
           );
sendmail(%mail) or die $Mail::Sendmail::error;
print "OK.\n", $Mail::Sendmail::log;

    [download]

    Answer: A cross-platform solution!

[reply]
[d/l]
[select]
      An interesting approach... I'd just finished refining my old code but now have something new to look at and play with, thank you very much Mr. Muskrat much appreciated!
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        barrd, that is why am here! To help: myself by learning and others by sharing what I have learned.

        When I saw that you were using a *nix specific way of doing it, I knew that someone else would come along one day and ask how to do it on Windows. I could have written a Windows specific version without much effort but why? I didn't want to make it specific to any one OS.

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