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Text File  |  1994-01-04  |  3KB  |  67 lines
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  10.                     ›1mControl›22m ›1mMessage›22m ›1mImplementation›22m ›1min›22m ›1mC›22m ›1mNews›22m
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  12.                                  ›4mGeoff›24m ›4mCollyer›24m
  13.                             Department of Statistics
  14.                              University of Toronto
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  17.           ›1mIntroduction›22m
  18.                Netnews  ›4mcontrol›24m  ›4mmessages›24m are ordinary­looking netnews
  19.           articles which contain the special  header  ›1mControl:›22m.   Such
  20.           articles are filed in the pseudo­newsgroup ›4mcontrol›24m and cause
  21.           related actions by the local news system, such as mailing  a
  22.           file to the poster of the control message.
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  24.           ›1mBuilt­ins›22m
  25.                ›1mihave›22m,  ›1msendme›22m,  and  ›1mcancel›22m  are handled internally by
  26.           ›4mrelaynews›24m,  because  processes  cannot  share  open   ›4mdbm›24m(3)
  27.           databases, there is no standard way to close them, and these
  28.           control messages read or write the ›4mhistory›24m files,  including
  29.           the  ›4mdbm›24m files.  ›4mIhave›24m and ›4msendme›24m are also permitted to have
  30.           message­id arguments containing ›1m<›22m and ›1m>›22m, both of  which  are
  31.           rejected by ›4mrelaynews›24m in arguments to externally­implemented
  32.           control messages, since they are shell metacharacters (›1m/›22m and
  33.           ›1m..›22m   are also bounced) and could be indicative of an attempt
  34.           to do something nasty.
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  36.           ›1mNormal›22m ›1mControl›22m ›1mMessages›22m
  37.                Most control messages are implemented by  ›4mrelaynews›24m  by
  38.           executing  the command following ›1mControl:›22m with a search path
  39.           of ›4m$NEWSCTL/bin:$NEWSBIN/ctl›24m and with standard input set  to
  40.           the control message article.  The command inherits the stan­
  41.           dard news search path and ›4mrelaynews›24m's user  and  group  ids,
  42.           typically  ›4mnews›24m; this can be important to gain access rights
  43.           to control files.   The  news  system  will  be  locked  (by
  44.           ›4m$NEWSCTL›24m/lock) while the command runs, because this is often
  45.           important for manipulating control files from  the  command,
  46.           and  because the news system is locked while ›4mrelaynews›24m runs.
  47.           If that command returns non­zero exit status, mail  is  sent
  48.           to  ›4m$NEWSMASTER›24m (usually ›1musenet›22m).  Standard output and stan­
  49.           dard  error  often  are  redirected  to   ›4m$NEWSCTL›24m/log   and
  50.           ›4m$NEWSCTL›24m/errlog  respectively;  invocations  of ›4mrelaynews›24m by
  51.           ›4minews›24m are exceptions.
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