How do I output an individual eqn described equation to a .ps or .eps?

I would like to reuse the output from eqn to get PS or EPS files which contains just the equation and not a complete A4 with the equation. If I try: $ cat test.eqn .EQ For ~ y=1 ~ -> ~ L( y hat , y) = -log( y hat ) ~ -> ~ if ~ y hat approx 1 ~ then ~ L( y hat , y ) approx 0 .EN $ cat test.eqn | eqn | groff -Tps > test.ps I get test.ps generated and I can see the equation properly formatted, but it is displayed as part of a complete page (either A4 or letter size). What shall be done to get just a document which contains just the required size to contain the equation? i.e. the whole page would had been cropped to the necessary space to contain the equation. Additionally, if I try to use troff instead of groff I can not manage to get PS code, why? (FreeBSD 12).