APLX Help : Help on APL language : System Functions & Variables : ⎕NSIZE Get size of native file
⎕NSIZE Return file size information
The ⎕NSIZE function returns the current size in bytes of a tied file as an integer scalar :
R ← ⎕NSIZE TIENO
APLX Help : Help on APL language : System Functions & Variables : ⎕NSIZE Get size of native file