CDO

hello everyone, could someone help me?
I'm trying to make a mask for a netcdf file just from my study area, which is the shapefile area that I have.
I used an NCL script to transform my shapefile file into netcdf. So you can use it in the CDO to make the mask. However, the CDO cannot read the file I created with the NCL
the script I used was this one, proposed by a user of this forum

load "/usr/local/lib/ncarg/nclscripts/shapefile_utils.ncl" ; 
        begin
            shpname  = "/home/Luiz/bacia_ama_bolivia.shp" 
            maskname = "/home/Luiz/mask_bolivia.nc" 
            print_shapefile_info(shpname)
            ;-- open data file to get the grid to be used
            f = addfile("GPM_DJF.nc","r")
            ;print(f)
            vNames = getfilevarnames (f) ; Pegar o nome das variaveis no arquivo
            ;print(vNames) ; mostrar o nome das variaveis
            ; Devem estar os nomes de cada variavel do arquivo selecionado
            ;-- read variable
            var                    =  f->GPM_3IMERGM_06_precipitation(:,:)
            var@lat2d              =  f->lat_bnds
            var@lon2d              =  f->lon_bnds
            ;-- shapefile mask resources
            opt             =  True
            opt@return_mask =  True    ;-- this forces the return of a 0s and 1s mask array
            ;-- create the mask based on the given shapefile
            mask_array             =  shapefile_mask_data(var, shpname, opt)
            mask_array!0           = "y" 
            mask_array!1           = "x" 
            mask_array@coordinates = "lat_bnds lon_bnds" 
            ;-- create new netCDF file and write mask array
            system("rm f " + maskname)
            fout = addfile(maskname,"c")
            fout>mask_array =  mask_array
            fout->lat_bnds      =  f->lat_bnds
            fout->lon_bnds     =  f->lon_bnds
            df = addfile("mask_bolivia.nc","r")
            print(df)
        end

what am i doing wrong? can anybody help me