Control:

Control: ヘッダー (USENET)

[3] USENET ニュースControl: は、制御メッセージの指示を記述するヘッダーです。

仕様書

歴史

[2] RFC 1036 2.2.6. Control

If a message contains a "Control" line, the message is a control message. Control messages are used for communication among USENET host machines, not to be read by users. Control messages are distributed by the same newsgroup mechanism as ordinary messages. The body of the "Control" header line is the message to the host.

For upward compatibility, messages that match the newsgroup pattern "all.all.ctl" should also be interpreted as control messages. If no "Control" header is present on such messages, the subject is used as the control message. However, messages on newsgroups matching this pattern do not conform to this standard.

Also for upward compatibility, if the first 4 characters of the "Subject:" line are "cmsg", the rest of the "Subject:" line should be interpreted as a control message.

son-of-RFC1036 6.6. Control

          The  Control  header  content marks the article as a control
          message, and specifies the desired actions (other  than  the
          usual ones of filing and passing on the article):
               Control-content  = verb *( space argument )
               verb             = 1*( letter / digit )
               argument         = 1*<ASCII printable character>
          The  verb  indicates  what  action  should be taken, and the
          argument(s) (if any) supply details.   In  some  cases,  the
          body  of  the  article  may also contain details.  Section 7
          describes the standard verbs.   See  also  the  Also-Control
          header (section 6.15).
               NOTE:  Control  messages  are  often processed and
               filed rather differently than normal articles.
               NOTE: The restriction of verbs to letters and dig-
               its  is new, but is consistent with existing prac-
               tice and potentially simplifies implementation  by
               avoiding  characters significant to command inter-
               preters.  Beware that the arguments are  under  no
               such restriction in general.
               NOTE:  Two  other  conventions  for distinguishing
               control messages from normal  articles  were  for-
               merly  in  use:  a  three-component newsgroup name
               ending in  ".ctl"  or  a  subject  beginning  with
               "cmsg "  was  considered to imply that the article
               was a  control  message.   These  conventions  are
               obsolete.  Do not use them.
          An  article  with  a  Control  header MUST not have an Also-
          Control or Supersedes header.