•         advanced

• RubyNetCDF provides all the functionality of the netCDF-3 C library
• Also supports OPeNDAP remote access
• Makes available combination functions such as iterators (which offer abstract ways to scan files and variables)
• Supports efficient multidimensional numeric arrays with the NArray library, the de facto Ruby standard
• Handles packed data specified by scale_factor and add_offset attributes

• Array index order is column-major (fastest varying dimension first, as in Fortran), but array indices start at 0.

The following is all the Ruby code needed to copy a netCDF file using only the Ruby interface:

# Usage
# ruby copy.rb filename_from filename_to

def usage
"\n\nUSAGE:\n% ruby #{$0} filename_from filename_to\n"
end

require "numru/netcdf"              # "numru" is Numerical Ruby suite
include NumRu
raise usage if ARGV.length != 2     # error if wrong number of args
filename_from, filename_to = ARGV
from = NetCDF.open(filename_from)   # open a NetCDF dataset(default:readonly)
to = NetCDF.create(filename_to)
from.each_dim{|dim| to.def_dim( dim.name, dim.length_ul0 )} # preserve unlimited
from.each_att{|att| to.put_att( att.name, att.get )}     # copy global atts
from.each_var{|var|
  newvar = to.def_var( var.name, var.ntype, var.dim_names )
  var.each_att{|att| newvar.put_att( att.name, att.get )}
}
to.enddef
from.each_var{|var| to.var(var.name).put(var.get)}
to.close

Here, each_dim, each_att, and each_var are iterators. The each_att method handles global attributes if applied to a NetCDF dataset; if it is applied to a variable, it handles the variable's attributes.

2008 Unidata NetCDF Workshop for Developers and Data Providers > NetCDF APIs

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