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(elisp)Process Buffers

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Process Buffers
---------------

   A process can (and usually does) have an "associated buffer", which
is an ordinary Emacs buffer that is used for two purposes: storing the
output from the process, and deciding when to kill the process.  You
can also use the buffer to identify a process to operate on, since in
normal practice only one process is associated with any given buffer.
Many applications of processes also use the buffer for editing input to
be sent to the process, but this is not built into Emacs Lisp.

   Unless the process has a filter function (Note: Filter Functions),
its output is inserted in the associated buffer.  The position to insert
the output is determined by the `process-mark', which is then updated
to point to the end of the text just inserted.  Usually, but not
always, the `process-mark' is at the end of the buffer.

 - Function: process-buffer process
     This function returns the associated buffer of the process PROCESS.

          (process-buffer (get-process "shell"))
               => #<buffer *shell*>

 - Function: process-mark process
     This function returns the process marker for PROCESS, which is the
     marker that says where to insert output from the process.

     If PROCESS does not have a buffer, `process-mark' returns a marker
     that points nowhere.

     Insertion of process output in a buffer uses this marker to decide
     where to insert, and updates it to point after the inserted text.
     That is why successive batches of output are inserted
     consecutively.

     Filter functions normally should use this marker in the same
     fashion as is done by direct insertion of output in the buffer.  A
     good example of a filter function that uses `process-mark' is
     found at the end of the following section.

     When the user is expected to enter input in the process buffer for
     transmission to the process, the process marker separates the new
     input from previous output.

 - Function: set-process-buffer process buffer
     This function sets the buffer associated with PROCESS to BUFFER.
     If BUFFER is `nil', the process becomes associated with no buffer.

 - Function: get-buffer-process buffer-or-name
     This function returns the process associated with BUFFER-OR-NAME.
     If there are several processes associated with it, then one is
     chosen.  (Currently, the one chosen is the one most recently
     created.)  It is usually a bad idea to have more than one process
     associated with the same buffer.

          (get-buffer-process "*shell*")
               => #<process shell>

     Killing the process's buffer deletes the process, which kills the
     subprocess with a `SIGHUP' signal (Note: Signals to Processes).


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