Commit 23dd4ecd authored by Eli Zaretskii's avatar Eli Zaretskii
Browse files

(System Processes): New section.

(Processes, Signals to Processes): Add xrefs to it.
parent b1bad9f3
......@@ -29,10 +29,14 @@ signals, obtain status information, receive output from the process, or
send input to it.
@defun processp object
This function returns @code{t} if @var{object} is a process,
@code{nil} otherwise.
This function returns @code{t} if @var{object} represents an Emacs
subprocess, @code{nil} otherwise.
@end defun
In addition to subprocesses of the current Emacs session, you can
also access other processes running on your machine. @xref{System
Processes}.
@menu
* Subprocess Creation:: Functions that start subprocesses.
* Shell Arguments:: Quoting an argument to pass it to a shell.
......@@ -46,6 +50,7 @@ This function returns @code{t} if @var{object} is a process,
* Output from Processes:: Collecting output from an asynchronous subprocess.
* Sentinels:: Sentinels run when process run-status changes.
* Query Before Exit:: Whether to query if exiting will kill a process.
* System Processes:: Accessing other processes running on your system.
* Transaction Queues:: Transaction-based communication with subprocesses.
* Network:: Opening network connections.
* Network Servers:: Network servers let Emacs accept net connections.
......@@ -1028,7 +1033,7 @@ This function sends a signal to process @var{process}. The argument
The @var{process} argument can be a system process @acronym{ID}; that
allows you to send signals to processes that are not children of
Emacs.
Emacs. @xref{System Processes}.
@end defun
@node Output from Processes
......@@ -1566,6 +1571,185 @@ is like this:
@end smallexample
@end defun
@node System Processes
@section Accessing Other Processes
@cindex system processes
In addition to accessing and manipulating processes that are
subprocesses of the current Emacs session, Emacs Lisp programs can
also access other processes running on the same machine. We call
these @dfn{system processes}, to distinguish between them and Emacs
subprocesses.
Emacs provides several primitives for accessing system processes.
Not all platforms support these primitives; on those which don't,
these primitives return @code{nil}.
@defun list-system-processes
This function returns a list of all the processes running on the
system. Each process is identified by its @acronym{PID}, a numerical
process ID that is assigned by the OS and distinguishes the process
from all the other processes running on the same machine at the same
time.
@end defun
@defun system-process-attributes pid
This function returns an alist of attributes for the process specified
by its process ID @var{pid}. Each association in the alist is of the
form @code{(@var{key} . @var{value})}, where @var{key} designates the
attribute and @var{value} is the value of that attribute. The various
attribute @var{key}'s that this function can return are listed below.
Not all platforms support all of these attributes; if an attribute is
not supported, its association will not appear in the returned alist.
Values that are numbers can be either integer or floating-point,
depending on the magnitude of the value.
@table @code
@item euid
The effective user ID of the user who invoked the process. The
corresponding @var{value} is a number. If the process was invoked by
the same user who runs the current Emacs session, the value is
identical to what @code{user-uid} returns (@pxref{User
Identification}).
@item user
User name corresponding to the process's effective user ID, a string.
@item egid
The group ID of the effective user ID, a number.
@item group
Group name corresponding to the effective user's group ID, a string.
@item comm
The name of the command that runs in the process. This is a string
that usually specifies the name of the executable file of the process,
without the leading directories. However, some special system
processes can report strings that do not correspond to an executable
file of a program.
@item state
The state code of the process. This is a short string that encodes
the scheduling state of the process. Here's a list of the most
frequently seen codes:
@table @code
@item ``D''
uninterruptible sleep (usually I/O)
@item ``R''
running
@item ``S''
interruptible sleep (waiting for some event)
@item ``T''
stopped, e.g., by a job control signal
@item ``Z''
``zombie'': a process that terminated, but not reaped by its parent
@end table
@noindent
For the full list of the possible states, see the manual page of the
@command{ps} command.
@item ppid
The process ID of the parent process, a number.
@item pgrp
The process group ID of the process, a number.
@item sess
The session ID of the process. This is a number that is the process
ID of the process's @dfn{session leader}.
@item ttname
A string that is the name of the process's controlling terminal. On
Unix and GNU systems, this is normally the file name of the
corresponding terminal device, such as @file{/dev/pts65}.
@item tpgid
The numerical process group ID of the foreground process group that
uses the process's terminal.
@item minflt
The number of minor page faults caused by the process since its
beginning. (Minor page faults are those that don't involve reading
from disk.)
@item majflt
The number of major page faults caused by the process since its
beginning. (Major page faults require a disk to be read, and are thus
more expensive than minor page faults.)
@item cminflt
@itemx cmajflt
Like @code{minflt} and @code{majflt}, but include the number of page
faults for all the child processes of the given process.
@item utime
Time spent by the process in the user context, for running the
application's code. The corresponding @var{value} is in the
@w{@code{(@var{high} @var{low} @var{microsec})}} format, the same
format used by functions @code{current-time} (@pxref{Time of Day,
current-time}) and @code{file-attributes} (@pxref{File Attributes}).
@item stime
Time spent by the process in the system (kernel) context, for
processing system calls. The corresponding @var{value} is in the same
format as for @code{utime}.
@item cutime
@itemx cstime
Like @code{utime} and @code{stime}, but includes the times of all the
child processes of the given process.
@item pri
The numerical priority of the process.
@item nice
The @dfn{nice value} of the process, a number. Processes with smaller
nice value get scheduled more favorably.
@item thcount
The number of threads in the process.
@item start
The time the process was started, in the @w{@code{(@var{high}
@var{low} @var{microsec})}} format used by @code{current-time} and
@code{file-attributes}.
@item etime
The time elapsed since the process started, in the @w{@code{(@var{high}
@var{low} @var{microsec})}} format.
@item vsize
The virtual memory size of the process, measured in kilobytes.
@item rss
The size of the process's @dfn{resident set}, the number of kilobytes
occupied by the process in the machine's physical memory.
@item pcpu
The percentage of the CPU time used by the process since it started.
The corresponding @var{value} is a floating-point number between 0 and
100.
@item pmem
The percentage of the total physical memory installed on the machine
used by the process's resident set. The value is a floating-point
number between 0 and 100.
@item args
The command-line with which the process was invoked. This is a string
in which individual command-line arguments are separated by blanks;
whitespace characters that are embedded in the arguments are quoted as
appropriate for the system's shell: escaped by backslash characters on
GNU and Unix, and enclosed in double quote characters on Windows.
Thus, this command-line string can be directly used in primitives such
as @code{shell-command}.
@end table
@end defun
@node Transaction Queues
@section Transaction Queues
@cindex transaction queue
......
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