electrostatic grid modelling using VMD

[yus...@mit.edu]

Dear all,

I am a beginner for VMD software, and currently try to practice VMD to get
electrostatic grid of protein of my interest. I try to use the example of
potsel.tcl usage in (http://www.ks.uiuc.edu/Research/vmd/script_library/)

source potsel.tcl
mol pdbload 1bnf
set sel [atomselect top "not water"]
potSel $sel 63 2 80

But, it did not work out, and written

couldn't execute "touch": no such file or directory

Do you know how I can get the "touch" file?
If you have more examples for me, I will really appreciate it.

Thanks a lot in advance.

Best regards,
Yusdy