This driver implements "unaddressed listen only mode", which is what
printers and plotters commonly do on GP-IB busses.
This means that you can capture print/plot like output from your
instruments by configuring them as necessary (good luck!) and
cat -u /dev/gpib0l > /tmp/somefile
Since there is no way to know when no more output is comming you
will have to ctrl-C the cat process when it is done (that is why
the -u is important).