fix/print for thermo variables

I never noticed this before, but fix/print does not seem to recognize the thermo system variables (vol, press, etc.) in the same way as other commands.

For example,

fix result all print 1000 “vol” file vol.out

prints a literal “vol” for every time step.

fix result all print 1000 “$vol” file vol.out

gives an illegal substitution.

Do you need to cast thermo variables as a regular variables in fix/print, cf.,

variable VOL equal vol

fix result all print 1000 "${VOL} " file vol.out

or did I miss something?

Thanks.

variable VOL equal vol
fix result all print 1000 "${VOL} " file vol.out

yes, that is the way to do it.

Something like

fix print 1000 "vol = vol" to get output like "vol = 3000.0"
could not work. How can it distinguish
strings from variables?

Steve