Assigning a new value to this attribute will cause any previously opened SourceFile to be closed. The first subsequent call to astRead will attempt to open the new file (an error will be reported if the file cannot be opened), and read data from it. All subsequent call to astRead will read data from the new file, until the SourceFile attribute is cleared or changed.
Clearing the attribute causes any open SourceFile to be closed. All subsequent data reads will use the source function specified when the Channel was created, or will read from standard input if no source function was specified.
If no value has been assigned to SourceFile, a null string will be returned if an attempt is made to get the attribute value.
AST A Library for Handling World Coordinate Systems in Astronomy