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NetCDF Operations

This chapter presents the interfaces of the netCDF routines that deal with a netCDF file as a whole.

A netCDF file that has not yet been opened can only be referred to by its file name. Once a netCDF file is opened, it is referred to by an ID, which is a small nonnegative integer returned when you create or open the file. A netCDF ID is a file handle, much like a file descriptor in C or a logical unit number in FORTRAN. In any single program, the netCDF IDs of distinct open netCDFs are distinct. A single netCDF file may be opened multiple times and will then have multiple distinct netCDF IDs; however at most one of the open instances of a single netCDF file should permit writing. When an open netCDF file is closed, its ID no longer refers to it, and that ID may be subsequently reassigned to refer to a different netCDF that is opened later.

The operations supported on a netCDF file as a single object are:

• Create, given file path and whether to overwrite or not.

• Open for access, given file path and read or write intent.

• Put into define mode, to add dimensions, variables, or attributes.

• Take out of define mode, checking consistency of additions.

• Close, writing to disk if required.

• Get number of dimensions, number of variables, number of global attributes, and ID of the unlimited dimension if any.

• Synchronize to disk to make sure it is current.

• Set and unset nofill mode for optimized sequential writes.

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