XPAT header range|<message-id> pat [pat...]

    The XPAT command is used to retrieve specific headers from
    specific articles, based on pattern matching on the contents of
    the header. This command was first available in INN.

    The required header parameter is the name of a header line (e.g.
    "subject") in a news group article. See RFC-1036 for a list
    of valid header lines. The required range argument may be
    any of the following:
                an article number
                an article number followed by a dash to indicate
                   all following
                an article number followed by a dash followed by
                   another article number

    The required message-id argument indicates a specific
    article. The range and message-id arguments are mutually
    exclusive. At least one pattern in wildmat must be specified
    as well. If there are additional arguments the are joined
    together separated by a single space to form one complete
    pattern. Successful responses start with a 221 response
    followed by a the headers from all messages in which the
    pattern matched the contents of the specified header line. This
    includes an empty list. Once the output is complete, a period
    is sent on a line by itself. If the optional argument is a
    message-id and no such article exists, the 430 error response
    is returned. A 502 response will be returned if the client only
    has permission to transfer articles.

2.9.1 Responses

        221 Header follows
        430 no such article
        502 no permission