Summarize netcdf variables into text file

Usage

nc_write_varfiles(nc_dir, write_mode = c("paired", "collected"))

nc_dir: directory to scan for netCDF files (including in subdirs)
write_mode: how many files to write: "paired" creates files named .nc.varalongside every.nc, "collected" writes a single <nc_dir>/nc_vars.txt` that lists every variable defined in any nc file in the directory