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.
By default, process output is inserted in the associated buffer.
(You can change this by defining a custom filter function,
see Filter Functions.) 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.
Killing the associated buffer of a process also kills the process.
Emacs asks for confirmation first, if the process’s
process-query-on-exit-flag is non-
nil (see Query Before Exit). This confirmation is done by the function
process-kill-buffer-query-function, which is run from
kill-buffer-query-functions (see Killing Buffers).
This function returns the associated buffer of the specified process.
(process-buffer (get-process "shell")) ⇒ #<buffer *shell*>
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.
The default filter function uses this marker to decide where to insert process output, and updates it to point after the inserted text. That is why successive batches of output are inserted consecutively.
Custom filter functions normally should use this marker in the same fashion.
For an example of a filter function that uses
see Process Filter Example.
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.
This function sets the buffer associated with process to
buffer. If buffer is
nil, the process becomes
associated with no buffer.
This function returns a nondeleted process associated with the buffer
specified by buffer-or-name. If there are several processes
associated with it, this function chooses one (currently, the one most
recently created, but don’t count on that). Deletion of a process
delete-process) makes it ineligible for this function to
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 (see Signals to Processes).
If the process’s buffer is displayed in a window, your Lisp program may wish to tell the process the dimensions of that window, so that the process could adapt its output to those dimensions, much as it adapts to the screen dimensions. The following functions allow communicating this kind of information to processes; however, not all systems support the underlying functionality, so it is best to provide fallbacks, e.g., via command-line arguments or environment variables.
set-process-window-sizeprocess height width
Tell process that its logical window size has dimensions
width by height, in character units. If this function
succeeds in communicating this information to the process, it returns
t; otherwise it returns
When windows that display buffers associated with process change their
dimensions, the affected processes should be told about these changes.
By default, when the window configuration changes, Emacs will
set-process-window-size on behalf of every
process whose buffer is displayed in a window, passing it the smallest
dimensions of all the windows displaying the process’s buffer. This
works via window-configuration-change-hook (see Window Hooks), which is told to invoke the function that is the value of
the variable window-adjust-process-window-size-function for
each process whose buffer is displayed in at least one window. You
can customize this behavior by setting the value of that variable.
The value of this variable should be a function of two arguments: a
process and the list of windows displaying the process’s buffer. When
the function is called, the process’s buffer is the current buffer.
The function should return a cons cell
(width . height) that describes the dimensions of the logical process
window to be passed via a call to
function can also return
nil, in which case Emacs will not call
set-process-window-size for this process.
Emacs supplies two predefined values for this variable:
window-adjust-process-window-size-smallest, which returns the
smallest of all the dimensions of the windows that display a process’s
returns the largest dimensions. For more complex strategies, write
your own function.
This variable can be buffer-local.
If the process has the
(see Process Information), its value overrides the global and
buffer-local values of