The functions close and fclose are equivalent, and can be used interchangeably.

Closes the specified file, which is assumed to have been opened either implicitly or by fopen or open.

fclose and close do not return anything.

Closing a file ensures that all data is actually written to disk.

When exiting Maple by the quit, done, or stop command, all open files are automatically closed.

Closing a file which exists but is not open is harmless.

The number of open files allowed is system specific.

When writing many files, you must fclose() each of them to ensure that you do not run out of file handles.

The fclose and close commands are thread safe as of Maple 15.  Care must be taken when closing files that are used by multiple threads in parallel.

Parallel calls to file i/o commands on the same file descriptor will be serialized in an arbitrary order.  If you need the commands to execute in a particular order you must use Maple's synchronization tools to enforce this.  See Threads:-Mutex.

For more information on thread safety, see index/threadsafe.