[NCO] extract a smaller area in a netCDF file

I want to create a smaller area with these new dimentions :
For the x coordinate : [1,300]
For the y coordinate : [ 250,800]

[pene@donunix] ncks -dx,,200 -dy,250,800 fic_in.nc fic_out.nc

[NCO] concatenate 2 netcdf files with differents variables

In two steps :

[pene@donunix] ncecat fic_in1.nc fic_out.nc
[pene@donunix] ncecat -A fic_in2.nc fic_out.nc