Simple I/O

Normally there will never be a need for applications to manage I/O at the lowest levels. Instead they will make use of the Configurator to access values from namelists and XIOS integration to obtain field data.

If you feel you might like to access files directly take into account that the existing methods encapsulate a lot of development and thought. In particular they are optimised for parallel running, e.g. read once and broadcast to all ranks. Doing it yourself can lead to problems.

If you do need to do it yourself a module io_utility_mod is provided which manages I/O unit numbers. This is critical to avoiding collisions with unit numbers already opened by other parts of the code.

Catch and Release

A pair of procedures are provided for accessing I/O units.

claim_io_unit is a function which returns a unit number and removes it from the pool of potential unit numbers.

release_io_unit gives the unit number back to the pool once you are done with it. Do not use the number after you have released it.

Open and Shut Case

A couple of cenvenience procedures are provided which not only claim an I/O unit but use it with a file.

open_file will claim a unit number or use the one provided and open a file on that unit for reading. All associated error checking is performed for you.

close_file closes the file on a given unit and releases the unit back to the pool along with all associated error checking.

Convenient Reading

There is even a function read_line which reads one text line from an I/O unit into a buffer. It performs error checking and returns a logical value indicating whether the end of the file has been reached which allows the call to be easily included in a loop over all lines in the file.