Perl regex in Nagios check - linux

Question

I am unfamiliar with perl, and I have a need to modify a Nagios check. I'd appreciate any advice on how to proceed. The check I'm using is check_smart, found here:
https://www.claudiokuenzler.com/nagios-plugins/check_smart.php
This script lets you check SMART values from hard drives and present the results in a simple form for monitoring. As it stands, the script can take a regex in the form /dev/sd[a-c] for one of the options; I believe that this is the section which allows this:
# list of devices for a loop
my(#dev);
if ( $opt_d ){
# normal mode - push opt_d on the list of devices
push(#dev,$opt_d);
} else {
# glob all devices - try '?' first
#dev =glob($opt_g);
}
foreach my $opt_dl (#dev){
warn "Found $opt_dl\n" if $opt_debug;
if (-b $opt_dl || -c $opt_dl){
$device .= $opt_dl.":";
} else {
warn "$opt_dl is not a valid block/character special device!\n\n" if $opt_debug;
}
}
I don't quite understand why the variable is $opt_dl when earlier it seems to be $opt_d. The result, however, is that the script returns something like:
OK: [/dev/sda] - Device is clean --- [/dev/sdb] - Device is clean --- [/dev/sdc] - Device is clean
EDIT: Here's the code where $opt_d is set; on further thought it seems like $opt_dl is just $opt_d while it's in a loop or something?
use vars qw($opt_b $opt_d $opt_g $opt_debug $opt_h $opt_i $opt_v);
Getopt::Long::Configure('bundling');
GetOptions(
"debug" => \$opt_debug,
"b=i" => \$opt_b, "bad=i" => \$opt_b,
"d=s" => \$opt_d, "device=s" => \$opt_d,
"g=s" => \$opt_g, "global=s" => \$opt_g,
"h" => \$opt_h, "help" => \$opt_h,
"i=s" => \$opt_i, "interface=s" => \$opt_i,
"v" => \$opt_v, "version" => \$opt_v,
);
The part of the code I'd like to change in a similar fashion is:
# Allow all device types currently supported by smartctl
# See http://www.smartmontools.org/wiki/Supported_RAID-Controllers
if ($opt_i =~ m/(ata|scsi|3ware|areca|hpt|cciss|megaraid|sat)/) {
$interface = $opt_i;
} else {
print "invalid interface $opt_i for $opt_d!\n\n";
print_help();
exit $ERRORS{'UNKNOWN'};
}
Specifically, I'd like to be able to pass the script something like "megaraid,[5-8]" and let it run for each. In this case, I would not be passing the regex for the device, it would just be /dev/sda.
If anyone could give me advice on this I'd appreciate it!

Answer 1

$opt_dl is probably poorly named and has nothing to do with your $opt_d, those are two separate variables.
From the if statement, if $opt_d is not set (that is the script was not given any device name to act upon), then glob is called with the value of $opt_g and it is glob in fact that finds out all filenames based on the regex given inside $opt_g.
After this if statement, the #dev array is filed with the names of devices to handle.
And then you have a foreach statement which means a loop on each item inside the #dev array. And during the loop, each item is in the $opt_dl variable, due to its use on the foreach statement.
However I was not able to understand what you wanted to do in your last paragraph.

Answer 2

I'm the maintainer of check_smart and it's funny I accidentally stumbled on that question now.
I don't quite understand why the variable is $opt_dl when earlier it seems to be $opt_d. The result, however, is that the script returns something like: OK: [/dev/sda] - Device is clean --- [/dev/sdb] - Device is clean --- [/dev/sdc] - Device is clean
So basically when you use the -g parameter, you tell the check_smart plugin to use glob (https://perldoc.perl.org/functions/glob.html) - this is not the same as regular expression. The drives matching the glob expression (e.g. -d '/dev/sd[a-z]) will create a list ($opt_dl) and the plugin will run through each drive in a for loop.
Specifically, I'd like to be able to pass the script something like "megaraid,[5-8]" and let it run for each. In this case, I would not be passing the regex for the device, it would just be /dev/sda.
This is already possible since release 5.0 (which was released in April 2014, way before your question ;-) ). You just need to change the syntax. Instead of using the glob expression on -d, you use it on the interface parameter (-i). Practical example: -i 'megaraid,[5-8]'.
Since the newest release (6.6, released a couple of days ago), the output for multiple drive checks (using -g) and hardware storage/raid controllers has slightly changed and now indicates the interface's device id rather than the logical drive path:
# ./check_smart.pl -g /dev/sda -i 'megaraid,[1-3]'
OK: [megaraid,1] - Device is clean --- [megaraid,2] - Device is clean --- [megaraid,3] - Device is clean|
This is all described in the official documentation, too.
More info:
https://www.claudiokuenzler.com/monitoring-plugins/check_smart.php
https://www.claudiokuenzler.com/blog/914/check_smart-6.6-multiple-drives-check-megaraid-3ware-cciss-controllers
I hope this answers your question, although I am probably 2 years late.