show command of gnuplot (read back the string)?

[gaaasa]

I'm writing a program like uniplot but then with some other functionality. I have to following problem,
I need to get back the settings for the gnuplot window and I'm using tcl/tk to create the interface

I open a channel to gnuplot.

set f0 [open "|gnuplot w+"]
..
plot curve
..
puts $f0 "show xrange"
flush $f0

Do you have an idea how I can get back the results of the "show command"? because when you are
using gnuplot the results of the show command won't come on the stdout and when I do something like

set string [gets $f1]

the string is empty
if you know a solution for this problem I would appreciate it very much if you would answer
the question

thanks in advanced Davy