2 Datasets
This chapter presents the interfaces of the netCDF functions that deal
with a netCDF dataset or the whole netCDF library.
A netCDF dataset that has not yet been opened can only be referred to
by its dataset name. Once a netCDF dataset is opened, it is referred
to by a netCDF ID, which is a small non-negative integer returned when
you create or open the dataset. A netCDF ID is much like a file
descriptor in C or a logical unit number in FORTRAN. In any single
program, the netCDF IDs of distinct open netCDF datasets are
distinct. A single netCDF dataset 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 dataset should permit
writing. When an open netCDF dataset is closed, the ID is no longer
associated with a netCDF dataset.
Functions that deal with the netCDF library include:
- Get version of library.
- Get error message corresponding to a returned error code.
The operations supported on a netCDF dataset as a single object are:
- Create, given dataset name and whether to overwrite or not.
- Open for access, given dataset name 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.
- Inquire about the 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.
- After a summary of conventions used in describing the netCDF
interfaces, the rest of this chapter presents a detailed description
of the interfaces for these operations.
