There is a utility program called "top"
that will give you all sorts of information
including memory and swapspace...
11:49am up 80 days, 22:35, 2 users, load average: 0.08, 0.03, 0.00
57 processes: 55 sleeping, 2 running, 0 zombie, 0 stopped
CPU states: 0.0% user, 0.1% system, 0.0% nice, 99.8% idle
Mem: 513536K av, 197540K used, 315996K free, 0K shrd, 24764K buff
Swap: 1542200K av, 0K used, 1542200K free 94740K cached
...you may or may not have it on your system.
you can get it at:
http://bioinfo1.mbfys.lu.se/TOP/ftptop.html