#file-name

A built-in stream shelf that provides the part of the SGML error message that names the file in which the error was found. This will be either the name of the main input file or the name of the file from which the text of an external entity was being read. This stream shelf can be accessed only from the header and body of sgml-error rules.

#file-name also can be used as a pattern variable for compatibility with past releases. However, this use is deprecated. Unlike programmer-defined pattern variables, #file-name must always be heralded with the pattern keyword, even where heralding is usually optional.

The is specified test is always true for #file-name because the file name is present in all SGML error messages.