Kind of, i.e. with MRTG by the same author, which uses rrdtool for generating graphics. Other tools as Cacti etc. might work as well.
RRDtool is only a completely generic graphing tool and it will plot whatever data you feed it.
Edit: I overlooked the "real time" part when answering. In this case, I assume rrdtool is not the right tool for you, as it is designed to be updated maybe once a minute or every five minutes or something like that. However, theoretically it should be possible to store data with a resolution down to a second and update a graph accordingly.
BTW, please look through the answers for your question and see if they solved your problems. If they did, accept them.
If you don't HAVE to use RRDTool, you could look at Graphite, which uses a processing backend called "carbon" that stores data in a database called "whisper". It's very "realtime". http://graphite.wikidot.com/faq#toc0
Kind of, i.e. with MRTG by the same author, which uses rrdtool for generating graphics. Other tools as Cacti etc. might work as well.
RRDtool is only a completely generic graphing tool and it will plot whatever data you feed it.
Edit: I overlooked the "real time" part when answering. In this case, I assume rrdtool is not the right tool for you, as it is designed to be updated maybe once a minute or every five minutes or something like that. However, theoretically it should be possible to store data with a resolution down to a second and update a graph accordingly.
BTW, please look through the answers for your question and see if they solved your problems. If they did, accept them.
If you don't HAVE to use RRDTool, you could look at Graphite, which uses a processing backend called "carbon" that stores data in a database called "whisper". It's very "realtime".
http://graphite.wikidot.com/faq#toc0
RRDtool is not meant for real-time, as Sven mentions.
On the command line, we are often using the old iptraf tool. It updates its counters every few seconds.