MARC::File - Base class for files of MARC records

       Andy Lester, "<andy@petdance.com>"

perl v5.36.0                                       2022-10-13                                    MARC::File(3pm)

       None.

       This code may be distributed under the same terms as Perl itself.

       Please  note  that  these  modules  are  not  products  of  or  supported by the employers of the various
       contributors to the code.

in()
       Opens a file for import. Ordinarily you will use "MARC::File::USMARC" or "MARC::File::MicroLIF" to do
       this.

           my $file = MARC::File::USMARC->in( 'file.marc' );

       Returns a "MARC::File" object, or "undef" on failure. If you encountered an error the error message will
       be stored in $MARC::File::ERROR.

       Optionally you can also pass in a filehandle, and "MARC::File".  will "do the right thing".

           my $handle = IO::File->new( 'gunzip -c file.marc.gz |' );
           my $file = MARC::File::USMARC->in( $handle );

   next([\&filter_func])
       Reads the next record from the file handle passed in.

       The $filter_func is a reference to a filtering function.  Currently, only USMARC records support this.
       See MARC::File::USMARC's "decode()" function for details.

       Returns a MARC::Record reference, or "undef" on error.

   skip()
       Skips over the next record in the file.  Same as "next()", without the overhead of parsing a record
       you're going to throw away anyway.

       Returns 1 or undef.

   warnings()
       Simlilar to the methods in MARC::Record and MARC::Batch, "warnings()" will return any warnings that have
       accumulated while processing this file; and as a side-effect will clear the warnings buffer.

   close()
       Closes the file, both from the object's point of view, and the actual file.

   write()
       Writes a record to the output file.  This method must be overridden in your subclass.

   decode()
       Decodes a record into a USMARC format.  This method must be overridden in your subclass.

       MARC::File - Base class for files of MARC records

       MARC::Record

           use MARC::File::USMARC;

           # If you have weird control fields...
           use MARC::Field;
           MARC::Field->allow_controlfield_tags('FMT', 'LDX');

           my $file = MARC::File::USMARC->in( $filename );

           while ( my $marc = $file->next() ) {
               # Do something
           }
           $file->close();
           undef $file;

       •   "out()" method

           We only handle files for input right now.