Once all input entries are sorted, the output index file can be
created. First the attribute bound to preamble is placed into
the output file, followed by the string
setpage_prefix N setpage_suffix,
provided N is the starting page number and
such a setting is requested. Next, each entry in the sorted list
is processed in order. Finally, the attribute bound to postamble
is appended at the end of the output file.
The algorithm for generating each entry with appropriate formatter-specific
commands or delimiters (i.e. item_i's, delim_i's, etc.)
is described in Reference [18].