Something similar to
write (unit, 100) eta, y
100 format(F4.1,3(',',F10.5))
should suffice, assuming that you take care of opening the file before writing to it, and closing the file after all the writing has been done.
Something similar to
write (unit, 100) eta, y
100 format(F4.1,3(',',F10.5))
should suffice, assuming that you take care of opening the file before writing to it, and closing the file after all the writing has been done.