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Zimwy · Dec 6, 2003, 02:13 PM

Hi,
I have a script that runs from Cron, when no user is logged into the system. Here's the script:

Code:
#!/usr/bin/perl

my $email_addr = '[email protected]';

$currentIP = `echo -n ipconfig getifaddr en0`;

if ($currentIP != "128.148.xxx.xxx"){
	#We've changed IPs! Send the email!
	&SendMail
}


sub SendMail {
	# Run or die quietly
	open( MAIL, "|/usr/sbin/sendmail -oi -t");

	print MAIL <<"EOF";
From: TheIMac\@oak.myvnc.com
To: $email_addr
Subject: New IP Address!
The new IP address of the imac is $currentIP
EOF

close(MAIL);
}

So, if I test this out manually by running, it works beautifully. But, if I run it from cron with no user logged in, the ipconfig getifaddr en0 returns nothing. Any advice?

Thanks!
gabe

chaldean oracle · Dec 6, 2003, 02:22 PM

Troubleshooting technique:

1. Hmmm... there's a problem with running ipconfig in cron, but not usually.

2. What causes problems running commands in different environments? Usually, an environment variable.

3. What environment variable could affect whether a command is run? A: the $PATH.

4. I wonder whether ipconfig might not be in the $PATH in the crontab?

5. which ipconfig
/usr/sbin/ipconfig

6. Ahh, so it's probably not in the $PATH in crontab.

7. Solution: change ipconfig to /usr/sbin/ipconfig in the script and you'll be all set.

chaldean oracle · Dec 6, 2003, 02:23 PM

Also, you might look into http://dyndns.org if all you want is to keep track of your machine.

Zimwy · Dec 7, 2003, 01:54 AM

Originally posted by chaldean oracle:
Troubleshooting technique:

1. Hmmm... there's a problem with running ipconfig in cron, but not usually.

2. What causes problems running commands in different environments? Usually, an environment variable.

3. What environment variable could affect whether a command is run? A: the $PATH.

4. I wonder whether ipconfig might not be in the $PATH in the crontab?

5. which ipconfig
/usr/sbin/ipconfig

6. Ahh, so it's probably not in the $PATH in crontab.

7. Solution: change ipconfig to /usr/sbin/ipconfig in the script and you'll be all set.

Thank you for your troubleshooting techniques. However, I would assume that if the command wasn't found, that perl would spit on an error, which would then get emailed to me since it's running as a cron job.

gabe

Juggle5 · Dec 7, 2003, 03:53 AM

This probably won't fix anything, but I do have question:

Since $currentIP is a string variable, do you have to use 'ne' (string compare) rather than '!=' (numerical compare) in the if statement:

if ($currentIP != "128.148.xxx.xxx"){

If I'm right, I don't understand how this would ever work, even when you were logged in. If I'm wrong, could you enlighten me? I'm always willing to learn.

Zim · Dec 7, 2003, 12:08 PM

hmm, well, I've had a script running cron for 2+ years now, that updates my IP to an FTP location just as a way way backup, in case all else goes wrong with my dyndns setup... it is

Code:
#!/usr/bin/perl -w

use strict;
use Cwd;
use Net::FTP;

my $ipfile = "/tmp/ip.html";
my $ip = "0.0.0.0";
my $ftp;
my $myip;
my $date = substr(scalar localtime,4,15);


open(IPFILE ,">$ipfile"); 
$ip = `/sbin/ifconfig -a | grep broadcast`;
($myip) = ($ip =~ m/inet\s+(\d+\.\d+\.\d+\.\d+)\s+netmask/);
print IPFILE "<html><head><title>IP Addr</title></head>
<body>
<p>$myip</p>
<p>updated: $date</p>
</body></html>\n";
close(IPFILE);

$ftp = Net::FTP->new("foo.bar.com",
                     Timeout => 30,
                     Debug   =>  1,
                     Passive =>  1)  or die "Can't connect $@\n";
$ftp->login("user","pass");
$ftp->put($ipfile,"ip.html") or die "Can't send ip.html $!\n";
$ftp->quit();

unlink("$ipfile");

cron entry

Code:
59 * * * * /Users/zimmy/bin/ip.pl > /dev/null 2>&1

I use ifconfig, not iconfig.. shrug.

Cheers,
Mike

si_lance · Dec 7, 2003, 09:57 PM

as a test trying making a wrapper shell script like:

#!/bin/bash
# this script will fire off script.pl from cron

/path/to/perl/script