The easiest way is to use a system dependent tool, and write a wrapper around it. And I most likely use a monitoring tool, be it a free one like 'mon' or 'big brother' or a commercial one like 'openview' or 'tivoli'. Some monitoring tools will already have swap space monitoring build in. For those who don't, I'd use Perl to mangle the output of the system dependent tool into input that can be parse by the monitoring tool. Such scripts are typically 10 lines or less, but will depend highly on the used front- and back-ends.

Abigail

Just in case your on Win32, here's how to obtain that information.

P:\test>perl -MWin32::SystemInfo CON
 Win32::SystemInfo::MemoryStatus(%m,'MB');
 printf '%15s := %15s'.$/, $_, $m{$_} for keys %m;
^Z
   TotalVirtual :=        2047.875
      TotalPage :=     501.4296875
      AvailPhys :=    112.84765625
      TotalPhys :=    223.23828125
        MemLoad :=               0
   AvailVirtual :=   2015.80859375
      AvailPage :=      308.515625
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Simple enough that Abigail wouldn't need to give up his day job if charged with this onerous task:)

The significant value as far "swap space" is concerned is the last value, AvailPage. Unsurprisingly, this is the amount of page file space currently available for use. It's when this value begins to approach 0 that you will get the infamous "You are running low on system resources" popup.

Actually, it appears to warn you when this is approach around 15MB, but I haven't been able to confirm this. Of course, but the time you reach this point, things are getting pretty sluggish, as most of the OS itself has also be swapped out by then

Ok, it would seem that you and I know about as much as each other about how to do this. Presumably you know something about swap space, where I do not, and clearly you do not know any perl whereas I do. So that makes us even. :-)

So, where to start? Well presumably there are some tools that you use routinely to monitor and manage your swapspace. Get em out and start figuring out how to parse them. That would mean using regexes, which are documented in perlre. You mention a config file. Well, personally I use Config::Inifile or plain oldData::Dumper to do this type of stuff, but a lot of people seem to be quite keen on YAML. Of course you'll want to exec the tools from the perl side of things so you should have a look at backticks, system and perlopentut.

Hopefully thats a good starting point?

% cat /proc/swaps
Filename                        Type            Size    Used    Priori
+ty
/dev/ide/host0/bus0/target1/lun0/part3 partition        2056312 0     
+  -1
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open IN, "</proc/swaps" or die "No swap file: $!\n";
<IN>;
my @fields = split <IN>;
$field[3] = 0 unless $field[3];
print "swap used = $field[3]\n";
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-Mark