It will save all video data sent from the camcorder in one or more huge AVI files with the name party_001.avi,p arty_002.avi and so on. The file size is slightly less than one GByte, which is a bit impractical though.
This example will create one AVI file with exactly 25 frames, which is 1 second duration with PAL video data and slightly less than 1 second with NTSC video data (use 30 frames to get 1 second duration for NTSC):
dvgrab --frames 25 party
This is the command line I use most of the times: it will save the video data into several AVI files with no more than 750 frames (30 seconds with a PAL camcorder). It starts a new file whenever it detects a new recording or when the frame count is exceeded and it also puts the date and time of recording into the file name.