elisp: Process Information
36.6 Process Information
========================
Several functions return information about processes.
-- Command: list-processes &optional query-only buffer
This command displays a listing of all living processes. In
addition, it finally deletes any process whose status was ‘Exited’
or ‘Signaled’. It returns ‘nil’.
The processes are shown in a buffer named ‘*Process List*’ (unless
you specify otherwise using the optional argument BUFFER), whose
major mode is Process Menu mode.
If QUERY-ONLY is non-‘nil’, it only lists processes whose query
flag is non-‘nil’. 
Query Before Exit.
-- Function: process-list
This function returns a list of all processes that have not been
deleted.
(process-list)
⇒ (#<process display-time> #<process shell>)
-- Function: get-process name
This function returns the process named NAME (a string), or ‘nil’
if there is none. The argument NAME can also be a process object,
in which case it is returned.
(get-process "shell")
⇒ #<process shell>
-- Function: process-command process
This function returns the command that was executed to start
PROCESS. This is a list of strings, the first string being the
program executed and the rest of the strings being the arguments
that were given to the program. For a network, serial, or pipe
connection, this is either ‘nil’, which means the process is
running or ‘t’ (process is stopped).
(process-command (get-process "shell"))
⇒ ("bash" "-i")
-- Function: process-contact process &optional key
This function returns information about how a network, a serial, or
a pipe connection was set up. When KEY is ‘nil’, it returns
‘(HOSTNAME SERVICE)’ for a network connection, ‘(PORT SPEED)’ for a
serial connection, and ‘t’ for a pipe connection. For an ordinary
child process, this function always returns ‘t’ when called with a
‘nil’ KEY.
If KEY is ‘t’, the value is the complete status information for the
connection, server, serial port, or pipe; that is, the list of
keywords and values specified in ‘make-network-process’,
‘make-serial-process’, or ‘make-pipe-process’, except that some of
the values represent the current status instead of what you
specified.
For a network process, the values include (see
‘make-network-process’ for a complete list):
‘:buffer’
The associated value is the process buffer.
‘:filter’
The associated value is the process filter function.
Filter Functions.
‘:sentinel’
The associated value is the process sentinel function.
Sentinels.
‘:remote’
In a connection, the address in internal format of the remote
peer.
‘:local’
The local address, in internal format.
‘:service’
In a server, if you specified ‘t’ for SERVICE, this value is
the actual port number.
‘:local’ and ‘:remote’ are included even if they were not specified
explicitly in ‘make-network-process’.
For a serial connection, see ‘make-serial-process’ and
‘serial-process-configure’ for the list of keys. For a pipe
connection, see ‘make-pipe-process’ for the list of keys.
If KEY is a keyword, the function returns the value corresponding
to that keyword.
-- Function: process-id process
This function returns the PID of PROCESS. This is an integral
number that distinguishes the process PROCESS from all other
processes running on the same computer at the current time. The
PID of a process is chosen by the operating system kernel when the
process is started and remains constant as long as the process
exists. For network, serial, and pipe connections, this function
returns ‘nil’.
-- Function: process-name process
This function returns the name of PROCESS, as a string.
-- Function: process-status process-name
This function returns the status of PROCESS-NAME as a symbol. The
argument PROCESS-NAME must be a process, a buffer, or a process
name (a string).
The possible values for an actual subprocess are:
‘run’
for a process that is running.
‘stop’
for a process that is stopped but continuable.
‘exit’
for a process that has exited.
‘signal’
for a process that has received a fatal signal.
‘open’
for a network, serial, or pipe connection that is open.
‘closed’
for a network, serial, or pipe connection that is closed.
Once a connection is closed, you cannot reopen it, though you
might be able to open a new connection to the same place.
‘connect’
for a non-blocking connection that is waiting to complete.
‘failed’
for a non-blocking connection that has failed to complete.
‘listen’
for a network server that is listening.
‘nil’
if PROCESS-NAME is not the name of an existing process.
(process-status (get-buffer "*shell*"))
⇒ run
For a network, serial, or pipe connection, ‘process-status’ returns
one of the symbols ‘open’, ‘stop’, or ‘closed’. The latter means
that the other side closed the connection, or Emacs did
‘delete-process’. The value ‘stop’ means that ‘stop-process’ was
called on the connection.
-- Function: process-live-p process
This function returns non-‘nil’ if PROCESS is alive. A process is
considered alive if its status is ‘run’, ‘open’, ‘listen’,
‘connect’ or ‘stop’.
-- Function: process-type process
This function returns the symbol ‘network’ for a network connection
or server, ‘serial’ for a serial port connection, ‘pipe’ for a pipe
connection, or ‘real’ for a subprocess created for running a
program.
-- Function: process-exit-status process
This function returns the exit status of PROCESS or the signal
number that killed it. (Use the result of ‘process-status’ to
determine which of those it is.) If PROCESS has not yet
terminated, the value is 0. For network, serial, and pipe
connections that are already closed, the value is either 0 or 256,
depending on whether the connection was closed normally or
abnormally.
-- Function: process-tty-name process
This function returns the terminal name that PROCESS is using for
its communication with Emacs—or ‘nil’ if it is using pipes instead
of a pty (see ‘process-connection-type’ in Asynchronous
Processes). If PROCESS represents a program running on a remote
host, the terminal name used by that program on the remote host is
provided as process property ‘remote-tty’. If PROCESS represents a
network, serial, or pipe connection, the value is ‘nil’.
-- Function: process-coding-system process
This function returns a cons cell ‘(DECODE . ENCODE)’, describing
the coding systems in use for decoding output from, and encoding
input to, PROCESS (Coding Systems).
-- Function: set-process-coding-system process &optional
decoding-system encoding-system
This function specifies the coding systems to use for subsequent
output from and input to PROCESS. It will use DECODING-SYSTEM to
decode subprocess output, and ENCODING-SYSTEM to encode subprocess
input.
Every process also has a property list that you can use to store
miscellaneous values associated with the process.
-- Function: process-get process propname
This function returns the value of the PROPNAME property of
PROCESS.
-- Function: process-put process propname value
This function sets the value of the PROPNAME property of PROCESS to
VALUE.
-- Function: process-plist process
This function returns the process plist of PROCESS.
-- Function: set-process-plist process plist
This function sets the process plist of PROCESS to PLIST.
Info Catalog
elisp: Deleting Processes
elisp: Processes
elisp: Input to Processes