# Combining variables into a netCDF (wsim_merge)¶

The wsim_merge utility provides a simple way to combine variables from multiple files into a single netCDF.

Variables are combined by calling wsim_merge with one or more --input arguments, each of which may import multiple variables, and an --output argument specifying where the combined file should be saved.

Attributes can be added to the resulting netCDF by specifying one or more --attr arguments. If an attribute is specified without a value (for example, --attr="temperature:units" instead of --attr="temperature:units=degree_C”, then the value will be copied from the source file.)