These are all the possible values for the IG_ISIS_TAG_OPENATTRIBUTE tag.

Values:

IG_ISIS_FILE_READ	Open file for read access.
IG_ISIS_FILE_WRITE	Open file for write access.
IG_ISIS_FILE_BOTH	Open file for read/write access.
IG_ISIS_OPENATTRIBUTE_CREATE	Create file if it doesn't exist.
IG_ISIS_OPENATTRIBUTE_DONTOPEN	Don't open existing file.
IG_ISIS_OPENATTRIBUTE_CREATEONLY	Only create a new file - fail if it already exists.
IG_ISIS_OPENATTRIBUTE_IFFLAGS	OR of all special flags.