I open a .sav file in PSPP (an open-source alternativ to SPSS) with
Now I would like to see how many rows there exist.
show n in regular old SPSS would do what you want. It doesn't appear to be in the list of commands for PSPP though.
Another possibility would be to compute your own variable based on the casenumber ($casenum), and then print the maximum casenumber. Something like below would do this.
compute #mynumber = $casenum. freq var #mynumber /format = notable /statistics = maximum.
I think you have to have the variable defined before running a frequency (i.e. I don't think you can do
freq var $casenum.). I don't have PSPP around to check, so let me know if this works in that program.