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The Art of Unix Programming
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Unix Programming - Data File Metaformats - Record-Jar Format

Record-Jar Format

Cookie-jar record separators combine well with the RFC 822 metaformat for records, yielding a format we'll call ‘record-jar’. If you need a textual format that will support multiple records with a variable repertoire of explicit fieldnames, one of the least surprising and human-friendliest ways to do it would look like Example5.4.

Of course, the record delimiter could be a blank line, but a line consisting of "%%\n" is more explicit and less likely to be introduced by accident during editing (two printable characters are better than one because it can't be generated by a single-character typo). In a format like this it is good practice to simply ignore blank lines.

If your records have an unstructured text part, your record-jar format is closely approaching a mailbox format. In this case, it's important that you have a well-defined way to escape the record delimiter so it can appear in text; otherwise, your record reader is going to choke on an ill-formed text part someday. Some technique analogous to byte-stuffing (described later in this chapter) is indicated.

Record-jar format is appropriate for sets of field-attribute associations that are like DSV files, but have a variable repertoire of fields, and possibly unstructured text associated with them.

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The Art of Unix Programming
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