Reload VCD file in gtkwave from command line

Question

I am using a VCD file generated by iverilog with gtkwave. There is a button present in the GUI, but I would like to reload the wave window from the command line. How would I go about that?

Answer 1

Someone on the GTKWave mailing list actually asked this same question a few years ago. It turns out that you can make GTKWave reload using gconftool2, of all things:

gconftool-2 --type string --set /com.geda.gtkwave/0/reload 0

Running the above command will cause GTKWave to reload the current waveform (as opposed to enabling some kind of auto-reload option, which you would think would be the case given that GConf is a configuration system).

Answer 2

You can run gtkwave in interactive mode, but this requires that your simulator is additive. Basically, your keeping the same previous data but adding additional data that has been collected. To do this, you add the "interactive" switch and you need to FIFO in the data.

From the user manual

Interactive VCD VCD files may be viewed as they are generated provided that they are written to a fifo (pipe) and are trampolined through shmidcat first (assume the simulator will normally generate outfile.vcd):

mkfifo outfile.vcd
cver myverilog.v &
shmidcat outfile.vcd | gtkwave ­v ­I myverilog.sav

You can then navigate the file as simulation is running and watch it update.