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NC3TONC4(1) General Commands Manual NC3TONC4(1)


nc3tonc4 - a program to convert netCDF 3 files to netCDF 4 format files


nc3tonc4 [-h] [-o] [--vars=var1,var2,..] [--zlib= (0|1)] [--complevel=(1-9)] [--shuffle=(0|1)] [--fletcher32=(0|1)] [--unpackshort= (0|1)] [--quantize=var1=n1,var2=n2,..] netcdf3filename netcdf4filename


This manual page documents briefly the nc3tonc4 command.
nc3tonc4 is a program that converts a netCDF 3 file into netCDF 4 format, optionally unpacking variables packed as short integers (with scale_factor and add_offset) to floats, and adding zlib compression (with the HDF5 shuffle filter and fletcher32 checksum). Data may also be quantized (truncated) to a specified precision to improve compression.


These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is included below.
Shows a summary of the available options.
Overwrite destination file (default is to raise an error if output file already exists).
A comma separated list of variable names to copy (default is to copy all variables).
Use NETCDF4_CLASSIC format instead of NETCDF4 (default = 1).
Activate (or disable) zlib compression (the default is to activate).
Set the zlib compression level (6 is default).
Activate (or disable) the shuffle filter (it is active by default).
Activate (or disable) the fletcher32 checksum (it is not active by default).
Unpack short integer variables to float variables using scale_factor and add_offset netCDF variable attributes (it is active by default).
--quantize=(comma separated list of variable name=integer pairs)
Truncate the data in the specified variables to a given decimal precision. For example, 'speed=2, height=-2, temp=0' will cause the variable 'speed' to be truncated to a precision of 0.01, 'height' to a precision of 100 and 'temp' to 1. This can significantly improve compression. The default is not to quantize any of the variables.
If set to 1, don't print any diagnostic information.
The number of records along unlimited dimension to write at once. The default is 10. It is ignored if there is no unlimited dimension. If chunk=0, it means write all the data at once.
The number of the record to start at along unlimited dimension. The default is 0. This option is ignored if there is no unlimited dimension.
The number of the record to stop at along unlimited dimension. The default is 1. This option is ignored if there is no unlimited dimension.


ncinfo(1), nc4tonc3(1).


This manual page was written by Ross Gammon <> based on the options displayed by nc3tonc4 -h.
22 Mar 2015