GNUS
====

GNUS is an Emacs subsystem for reading and responding to netnews.  You can use GNUS to browse through news groups, look at summaries of articles in specific group, and read articles of interest.  You can respond to authors or write replies to all the readers of a news group.

This section introduces GNUS and describes several basic features.  Full documentation will appear elsewhere.

To start GNUS, type M-x gnus RET.

GNUS's Three Buffers
--------------------

GNUS creates and uses three Emacs buffers, each with its own particular purpose and its own major mode.

The Newsgroup buffer contains a list of newsgroups.  This is the first buffer that GNUS displays when it starts up.  Normally the list contains only the newsgroups to which you subscribe (which are listed in your .newsrc file) and which contain unread articles.  Use this buffer to select a specific newsgroup.

The Summary buffer lists the articles in a single newsgroup, including their subjects, their numbers, and who posted them.  GNUS creates a Summary buffer for a newsgroup when you select the group in the Newsgroup buffer.  Use this buffer to select an article, and to move around in an article.

The Article buffer displays the text of an article.  You rarely need to select this buffer because you can read the text while keeping the Summary buffer selected.

When GNUS Starts Up
-------------------

At startup, GNUS reads your .newsrc news initialization file and attempts to communicate with the local news server, which is a repository of news articles.  The news server need not be the same computer you are logged in on.

If you start GNUS and connect to the server, but do not see any newsgroups listed in the Newsgroup buffer, type L to get a listing of all the newsgroups.  Then type u to unsubscribe from particular newsgroups.  (Move the cursor using n and p or the usual Emacs commands.)

When you quit GNUS with q, it automatically records in your .newsrc initialization file the subscribed or unsubscribed status of all newsgroups, except for groups you have ``killed''.  (You do not need to edit this file yourself, but you may.)  When new newsgroups come into existence, GNUS adds them automatically.

Summary of GNUS Commands
------------------------

Reading news is a two step process:

 1. Choose a newsgroup in the Newsgroup buffer.

 2. Select articles from the Summary buffer.  Each article selected is displayed in the Article buffer in a large window, below the Summary buffer in its small window.

Each buffer has commands particular to it, but commands that do the same things have similar keybindings.  Here are commands for the Newsgroup and Summary buffers:

z
     In the Newsgroup buffer, suspend GNUS.  You can return to GNUS later by selecting the Newsgroup buffer and typing g to get newly arrived articles.

q
     In the Newsgroup buffer, update your .newsrc initialization file and quit GNUS.

     In the Summary buffer, exit the current newsgroup and return to the Newsgroup buffer.  Thus, typing q twice quits GNUS.

L
     In the Newsgroup buffer, list all the newsgroups available on your news server.  This may be a long list!

l
     In the Newsgroup buffer, list only the newsgroups to which you subscribe and which contain unread articles.

u
     In the Newsgroup buffer, unsubscribe from (or subscribe to) the newsgroup listed in the line that point is on.  When you quit GNUS by typing q, GNUS lists your subscribed-to newsgroups in your .newsrc file.  The next time you start GNUS, you see only the newsgroups listed in your .newsrc file.

C-k
     In the Newsgroup buffer, ``kill'' the current line's newsgroup---don't show it in the Newsgroup buffer from now on.  This affects future GNUS sessions as well as the present session.

     When you quit GNUS by typing q, GNUS writes information in the file .newsrc describing all newsgroups except those you have ``killed.''

SPC
     In the Newsgroup buffer, select the group on the line under the cursor and display the first unread article in that group.

     In the Summary buffer,

       - Select the article on the line under the cursor if none is selected.

       - Scroll the text of the selected article (if there is one).

       - Select the next unread article if at the end of the current article.

     Thus, you can move through all the articles by repeatedly typing SPC.

DEL
     In the Newsgroup Buffer, move point to the previous newsgroup containing unread articles.

     In the Summary buffer, scroll the text of the article backwards.

n
     Move point to the next unread newsgroup, or select the next unread article.

p
     Move point to the previous unread newsgroup, or select the previous unread article.

C-n
C-p
     Move point to the next or previous item, even if it is marked as read. This does not select the article or newsgroup on that line.

s
     In the Summary buffer, do an incremental search of the current text in the Article buffer, just as if you switched to the Article buffer and typed C-s.

M-s REGEXP RET
     In the Summary buffer, search forward for articles containing a match for REGEXP.

C-c C-s C-n
C-c C-s C-s
C-c C-s C-d
C-c C-s C-a
     In the Summary buffer, sort the list of articles by number, subject, date, or author.

C-M-n
C-M-p
     In the Summary buffer, read the next or previous article with the same subject as the current article.

Sorting Text
============

Emacs provides several commands for sorting text in the buffer.  All operate on the contents of the region (the text between point and the mark).  They divide the text of the region into many sort records, identify a sort key for each record, and then reorder the records into the order determined by the sort keys.  The records are ordered so that their keys are in alphabetical order, or, for numeric sorting, in numeric order.  In alphabetic sorting, all upper case letters `A' through `Z' come before lower case `a', in accord with the ASCII character sequence.

The various sort commands differ in how they divide the text into sort records and in which part of each record is used as the sort key.  Most of the commands make each line a separate sort record, but some commands use paragraphs or pages as sort records.  Most of the sort commands use each entire sort record as its own sort key, but some use only a portion of the record as the sort key.

M-x sort-lines
     Divide the region into lines, and sort by comparing the entire text of a line.  A prefix argument means sort into descending order.

M-x sort-paragraphs
     Divide the region into paragraphs, and sort by comparing the entire text of a paragraph (except for leading blank lines).  A prefix argument means sort into descending order.

M-x sort-pages
     Divide the region into pages, and sort by comparing the entire text of a page (except for leading blank lines).  A prefix argument means sort into descending order.

M-x sort-fields
     Divide the region into lines, and sort by comparing the contents of one field in each line.  Fields are defined as separated by whitespace, so the first run of consecutive non-whitespace characters in a line constitutes field 1, the second such run constitutes field 2, etc.

     Specify which field to sort by with a numeric argument: 1 to sort by field 1, etc.  A negative argument means sort into descending order. Thus, minus 2 means sort by field 2 in reverse-alphabetical order.  If several lines have identical contents in the field being sorted, they keep same relative order that they had in the original buffer.

M-x sort-numeric-fields
     Like M-x sort-fields except the specified field is converted to a number for each line, and the numbers are compared.  10 comes before 2 when considered as text, but after it when considered as a number.

M-x sort-columns
     Like M-x sort-fields except that the text within each line used for comparison comes from a fixed range of columns.  See below for an explanation.

For example, if the buffer contains this:

     On systems where clash detection (locking of files being edited) is
     implemented, Emacs also checks the first time you modify a buffer
     whether the file has changed on disk since it was last visited or
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.

then applying M-x sort-lines to the entire buffer produces this:

     On systems where clash detection (locking of files being edited) is
     implemented, Emacs also checks the first time you modify a buffer
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.
     whether the file has changed on disk since it was last visited or

where the upper case O sorts before all lower case letters.  If you use C-u 2 M-x sort-fields instead, you get this:

     implemented, Emacs also checks the first time you modify a buffer
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.
     On systems where clash detection (locking of files being edited) is
     whether the file has changed on disk since it was last visited or

where the sort keys were Emacs, If, buffer, systems and the.

M-x sort-columns requires more explanation.  You specify the columns by putting point at one of the columns and the mark at the other column.  Because this means you cannot put point or the mark at the beginning of the first line to sort, this command uses an unusual definition of `region': all of the line point is in is considered part of the region, and so is all of the line the mark is in.

For example, to sort a table by information found in columns 10 to 15, you could put the mark on column 10 in the first line of the table, and point on column 15 in the last line of the table, and then run sort-columns.  Equivalently, you could run it with the mark on column 15 in the first line and point on column 10 in the last line.

This can be thought of as sorting the rectangle specified by point and the mark, except that the text on each line to the left or right of the rectangle moves along with the text inside the rectangle. See Rectangles.

Many of the sort commands ignore case differences when comparing, if sort-fold-case is non-nil.

Running Shell Commands from Emacs
=================================

Emacs has commands for passing single command lines to inferior shell processes; it can also run a shell interactively with input and output to an Emacs buffer *shell*.

M-!
     Run a specified shell command line and display the output (shell-command).

M-|
     Run a specified shell command line with region contents as input; optionally replace the region with the output (shell-command-on-region).

M-x shell
     Run a subshell with input and output through an Emacs buffer. You can then give commands interactively.

Single Shell Commands
---------------------

M-! (shell-command) reads a line of text using the minibuffer executes it as a shell command in a subshell made just for this command.  Standard input for the command comes from the null device.  If the shell command produces any output, the output goes into an Emacs buffer named *Shell Command Output*, which is displayed in another window but not selected.  A numeric argument, as in M-1 M-!, directs this command to insert any output into the current buffer.  In that case, point is left before the output and the mark is set after the output.

If the shell command line ends in &, it runs asynchronously.

M-| (shell-command-on-region) is like M-! but passes the contents of the region as input to the shell command, instead of no input.  If a numeric argument is used, meaning insert output in the current buffer, then the old region is deleted first and the output replaces it as the contents of the region.

Both M-! and M-| use shell-file-name to specify the shell to use.  This variable is initialized based on your SHELL environment variable when Emacs is started.  If the file name does not specify a directory, the directories in the list exec-path are searched; this list is initialized based on the environment variable PATH when Emacs is started.  Your .emacs file can override either or both of these default initializations.

With M-! and M-|, Emacs has to wait until the shell command completes.  To stop waiting, type C-g to quit; that also kills the shell command.

Interactive Inferior Shell
--------------------------

To run a subshell interactively, putting its typescript in an Emacs buffer, use M-x shell.  This creates (or reuses) a buffer named *shell* and runs a subshell with input coming from and output going to that buffer.  That is to say, any ``terminal output'' from the subshell goes into the buffer, advancing point, and any ``terminal input'' for the subshell comes from text in the buffer.  To give input to the subshell, go to the end of the buffer and type the input, terminated by RET.

Emacs does not wait for the subshell to do anything.  You can switch windows or buffers and edit them while the shell is waiting, or while it is running a command.  Output from the subshell waits until Emacs has time to process it; this happens whenever Emacs is waiting for keyboard input or for time to elapse.

To make multiple subshells, rename the buffer *shell* to something different using M-x rename-uniquely.  Then type M-x shell again to create a new buffer *shell* with its own subshell.  If you rename this buffer as well, you can create a third one, and so on.  All the subshells run independently and in parallel.

The file name used to load the subshell is the value of the variable explicit-shell-file-name, if that is non-nil.  Otherwise, the environment variable ESHELL is used, or the environment variable SHELL if there is no ESHELL.  If the file name specified is relative, the directories in the list exec-path are searched (see Single Shell Commands).

As soon as the subshell is started, it is sent as input the contents of the file ~/.emacs_SHELLNAME, if that file exists, where SHELLNAME is the name of the file that the shell was loaded from. For example, if you use bash, the file sent to it is ~/.emacs_bash.

cd, pushd and popd commands given to the inferior shell are watched by Emacs so it can keep the *shell* buffer's default directory the same as the shell's working directory.  These commands are recognized syntactically by examining lines of input that are sent.  If you use aliases for these commands, you can tell Emacs to recognize them also.  For example, if the value of the variable shell-pushd-regexp matches the beginning of a shell command line, that line is regarded as a pushd command.  Change this variable when you add aliases for pushd.  Likewise, shell-popd-regexp and shell-cd-regexp are used to recognize commands with the meaning of popd and cd.  These commands are recognized only at the beginning of a shell command line.

If Emacs gets an error while trying to handle what it believes is a cd, pushd or popd command, it runs the hook shell-set-directory-error-hook (see Hooks).

If Emacs does not properly track changes in the current directory of the subshell, use the command M-x dirs to ask the shell what its current directory is.  This command works for shells that support the most common command syntax; it may not work for unusual shells.

Shell Mode
----------

The shell buffer uses Shell mode, which defines several special keys attached to the C-c prefix.  They are chosen to resemble the usual editing and job control characters present in shells that are not under Emacs, except that you must type C-c first.  Here is a complete list of the special key bindings of Shell mode:

RET
     At end of buffer send line as input; otherwise, copy current line to end of buffer and send it (comint-send-input).  When a line is copied, any text at the beginning of the line that matches the variable shell-prompt-pattern is left out; this variable's value should be a regexp string that matches the prompts that your shell uses.

TAB
     Complete the file name before point in the shell buffer (comint-dynamic-complete).

M-?
     Display temporarily a list of the possible completions of the file name before point in the shell buffer (comint-dynamic-list-completions).

C-a
     Move to the beginning of the line, but after the prompt if any (comint-bol).

C-d
     Either delete a character or send EOF (comint-delchar-or-maybe-eof).  Typed at the end of the shell buffer, C-d sends EOF to the subshell.  Typed at any other position in the buffer, C-d deletes a character as usual.

C-c C-u
     Kill all text pending at end of buffer to be sent as input (comint-kill-input).

C-c C-w
     Kill a word before point (backward-kill-word).

C-c C-c
     Interrupt the shell or its current subjob if any (comint-interrupt-subjob).

C-c C-z
     Stop the shell or its current subjob if any (comint-stop-subjob).

C-c C-\
     Send quit signal to the shell or its current subjob if any (comint-quit-subjob).

C-c C-o
     Kill the last batch of output from a shell command (comint-kill-output).  This is useful if a shell command spews out lots of output that just gets in the way.

C-c C-r
     Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (comint-show-output).

M-x dirs
     Ask the shell what its current directory is, so that Emacs can agree with the shell.

M-x send-invisible RET TEXT RET
     Send TEXT as input to the shell, after reading it without echoing.  This is useful when a shell command runs a program that asks for a password.

M-x comint-continue-subjob
     Continue the shell process.  This is useful if you accidentally suspend the shell process. (You should not suspend the shell process. Suspending a subjob of the shell is a completely different matter--that is normal practice, but you must use the shell to continue the subjob; this command won't do it.)

Shell Command History
---------------------

Shell buffers support history commands much like the minibuffer history commands.

M-p
     Fetch the next earlier old shell command.

M-n
     Fetch the next later old shell command.

M-r REGEXP RET
M-s REGEXP RET
     Search backwards or forwards for old shell commands that match REGEXP.

Shell buffers provide a history of previously entered shell commands.  To reuse shell commands from the history, use the editing commands M-p, M-n, M-r and M-s.  These work just like the minibuffer history commands except that they operate on the text at the end of the shell buffer, the text that typing RET will send to the shell.

M-p fetches an earlier shell command to the end of the shell buffer. Successive use of M-p fetches successively earlier shell commands, each replacing any text that was already present as potential shell input. M-n does likewise except that it finds successively more recent shell commands from the buffer.

The history search commands M-r and M-s read a regular expression and search through the history for a matching command.  Aside from the choice of which command to fetch, they work just like M-p and M-r.  If you enter an empty regexp, these commands reuse the same regexp used last time.

When you find the previous input you want, you can resubmit it by typing RET, or you can edit it first and then resubmit it if you wish.

These commands get the text of previous shell commands from a special history list, not from the shell buffer itself.  Thus, editing the shell buffer, or even killing large parts of it, does not affect the history that these commands access.

Narrowing
=========

Narrowing means focusing in on some portion of the buffer, making the rest temporarily inaccessible.  The portion which you can still get to is called the accessible portion.  Cancelling the narrowing, and making the entire buffer once again accessible, is called widening.  The amount of narrowing in effect in a buffer at any time is called the buffer's restriction.

C-x n n
     Narrow down to between point and mark (narrow-to-region).

C-x n w
     Widen to make the entire buffer accessible again (widen).

C-x n p
     Narrow down to the current page (narrow-to-page).

When you have narrowed down to a part of the buffer, that part appears to be all there is.  You can't see the rest, you can't move into it (motion commands won't go outside the accessible part), you can't change it in any way.  However, it is not gone, and if you save the file all the inaccessible text will be saved.  In addition to sometimes making it easier to concentrate on a single subroutine or paragraph by eliminating clutter, narrowing can be used to restrict the range of operation of a replace command or repeating keyboard macro.  The word Narrow appears in the mode line whenever narrowing is in effect.

The primary narrowing command is C-x n n (narrow-to-region). It sets the current buffer's restrictions so that the text in the current region remains accessible but all text before the region or after the region is invisible.  Point and mark do not change.

Alternatively, use C-x n p (narrow-to-page) to narrow down to the current page.  See Pages, for the definition of a page.

The way to undo narrowing is to widen with C-x n w (widen). This makes all text in the buffer accessible again.

You can get information on what part of the buffer you are narrowed down to using the C-x = command.  See Position Info.

Because narrowing can easily confuse users who do not understand it, narrow-to-region is normally a disabled command.  Attempting to use this command asks for confirmation and gives you the option of enabling it; once you enable the command, confirmation will no longer be required for it.  See Disabling.

Hardcopy Output
===============

The Emacs commands for making hardcopy let you print either an entire buffer or just part of one, either with or without page headers. See also the hardcopy commands of Dired (see Misc File Ops) and the diary (see Diary Commands).

M-x print-buffer
     Print hardcopy of current buffer using Unix command print (lpr -p).  This makes page headings containing the file name and page number.

M-x lpr-buffer
     Print hardcopy of current buffer using Unix command lpr. This makes no page headings.

M-x print-region
     Like print-buffer but prints only the current region.

M-x lpr-region
     Like lpr-buffer but prints only the current region.

All the hardcopy commands pass extra switches to the lpr program based on the value of the variable lpr-switches.  Its value should be a list of strings, each string an option starting with -.  For example, to use a printer named nearme, set lpr-switches like this:

     (setq lpr-switches '("-Pnearme"))

Two-Column Editing
==================

Two-column mode lets you conveniently edit two side-by-side columns of text.  It uses two side-by-side windows, each showing its own buffer.

There are three ways to enter two-column mode:

C-x 6 2
     Enter two-column mode with the current buffer on the left, and on the right, a buffer whose name is based on the current buffer's name (tc-two-columns).  If the right-hand buffer doesn't already exist, it starts out empty; the current buffer's contents are not changed.

     This command is appropriate when the current buffer contains just one column and you want to add another column.

C-x 6 s
     Split the current buffer, which contains two-column text, into two buffers, and display them side by side (tc-split).  The current buffer becomes the left-hand buffer, but the text in the right-hand column is moved into the right-hand buffer.  The current column specifies the split point.  Splitting starts with the current line and continues to the end of the buffer.

     This command is appropriate when you have a buffer that already contains two-column text, and you wish to separate the columns temporarily.

C-x 6 b BUFFER RET
     Enter two-column mode using the current buffer as the left-hand buffer, and using buffer BUFFER as the right-hand buffer (tc-associate-buffer).

C-x 6 s looks for a column separator which is a string that appears on each line between the two columns.  You can specify the width of the separator with a numeric argument to C-x 6 s; that many characters, before point, constitute the separator string.  By default, the width is 1, so the column separator is the character before point.

When a line has the separator at the proper place, C-x 6 s puts the text after the separator into the right-hand buffer, and deletes the separator.  Lines that don't have the column separator at the proper place remain unsplit; they stay in the left-hand buffer, and the right-hand buffer gets an empty line to correspond.  (This is the way to write a line which ``spans both columns while in two-column mode: write it in the left-hand buffer, and put an empty line in the right-hand buffer.)

It's not a good idea to use ordinary scrolling commands during two-column editing, because that separates the two parts of each split line.  Instead, use these special scroll commands:

C-x 6 SPC
     Scroll both buffers up, in lockstep (tc-scroll-up).

C-x 6 DEL
     Scroll both buffers down, in lockstep (tc-scroll-down).

C-x 6 C-l
     Recenter both buffers, in lockstep (tc-recenter).

When you have edited both buffers as you wish, merge them with C-x 6 1 (tc-merge).  This copies the text from the right-hand buffer as a second column in the other buffer.  To go back to two-column editing, use C-x 6 s.

Use C-x 6 d to disassociate the two buffers, leaving each as it stands (tc-dissociate).  If the other buffer, the one not current when you type C-x 6 d, is empty, C-x 6 d kills it.

Editing Binary Files
====================

There is a special major mode for editing binary files: Hexl mode.  To use it, use M-x hexl-find-file instead of C-x C-f to visit the file.  This command converts the file's contents to hexadecimal and lets you edit the translation.  When you save the file, it is converted automatically back to binary.

You can also use M-x hexl-mode to translate an existing buffer into hex.  This is useful if you visit a file normally and then discover it is a binary file.

Ordinary text characters overwrite in Hexl mode.  This is to reduce the risk of accidentally spoiling the alignment of data in the file. There are special commands for insertion.  Here is a list of the commands of Hexl mode:

C-M-d
     Insert a byte with a code typed in decimal.

C-M-o
     Insert a byte with a code typed in octal.

C-M-x
     Insert a byte with a code typed in hex.

C-x [
     Move to the beginning of a 1k-byte ``page''.

C-x ]
     Move to the end of a 1k-byte ``page''.

M-g
     Move to an address specified in hex.

M-j
     Move to an address specified in decimal.

C-c C-c
     Leave Hexl mode, going back to the major mode this buffer had before you invoked hexl-mode.

Using Emacs as a Server
=======================

Various programs such as mail can invoke your choice of editor to edit a particular piece of text, such as a message that you are sending.  By convention, these programs use the environment variable EDITOR to specify which editor to run.  If you set EDITOR to emacs, they invoke Emacs---but in an inconvenient fashion, by starting a new, separate Emacs process.  This is inconvenient because it takes time and because the new Emacs process doesn't share the buffers in the existing Emacs process.

You can arrange to use your existing Emacs process as the editor for programs like mail by using the Emacs client and Emacs server programs.  Here is how.

First, the preparation.  Within Emacs, call the function server-start.  (Your .emacs file can do this automatically if you add the expression (server-start) to it.)  Then, outside Emacs, set the EDITOR environment variable to emacsclient.

Then, whenever any program invokes your specified EDITOR program, the effect is to send a message to your principal Emacs telling it to visit a file.  (That's what the program emacsclient does.) Emacs obeys silently; it does not immediately switch to the new file's buffer.  When you want to do that, type C-x # (server-edit).

When you've finished editing that buffer, type C-x # again. This saves the file and sends a message back to the emacsclient program telling it to exit.  The programs that use EDITOR wait for the ``editor'' (actually, emacsclient) to exit.  C-x # also checks to see if any other files are pending for you to edit, and selects the next one.

You can switch to a server buffer manually if you wish; you don't have to arrive at it with C-x #.  But C-x # is the only way to say that you are ``finished'' with one.

If you set the variable server-window to a window or a frame, C-x # displays the server buffer in that window or in that frame.

While mail or another application is waiting for emacsclient to finish, emacsclient does not read terminal input.  So the terminal that mail was using is effectively blocked for the duration.  In order to edit with your principal Emacs, you need to be able to use it without using that terminal.  There are two ways to do this:

  * Using a window system, run mail and the principal Emacs in two separate windows.  While mail is waiting for emacsclient, the window where it was running is blocked, but you can use Emacs by switching windows.

  * Use Shell mode in Emacs to run the other program such as mail; then, emacsclient blocks only the subshell under Emacs; you can still use Emacs to edit the file.

Some programs write temporary files for you to edit.  After you edit the temporary file, the program reads it back and deletes it.  If the Emacs server is later asked to edit the same file name, it should assume this has nothing to do with the previous occasion for that file name. The server accomplishes this by killing the temporary file's buffer when you finish with the file.  Use the variable server-temp-file-regexp to specify which files are temporary in this sense; its value should be a regular expression that matches file names that are temporary.

Recursive Editing Levels
========================

A recursive edit is a situation in which you are using Emacs commands to perform arbitrary editing while in the middle of another Emacs command.  For example, when you type C-r inside of a query-replace, you enter a recursive edit in which you can change the current buffer.  On exiting from the recursive edit, you go back to the query-replace.

Exiting the recursive edit means returning to the unfinished command, which continues execution.  To exit, type C-M-c (exit-recursive-edit).

You can also abort the recursive edit.  This is like exiting, but also quits the unfinished command immediately.  Use the command C-] (abort-recursive-edit) for this.  See Quitting.

The mode line shows you when you are in a recursive edit by displaying square brackets around the parentheses that always surround the major and minor mode names.  Every window's mode line shows this, in the same way, since being in a recursive edit is true of Emacs as a whole rather than any particular window or buffer.

It is possible to be in recursive edits within recursive edits.  For example, after typing C-r in a query-replace, you may type a command that enters the debugger.  This begins a recursive editing level for the debugger, within the recursive editing level for C-r. Mode lines display a pair of square brackets for each recursive editing level currently in progress.

Exiting the inner recursive edit (such as, with the debugger c command) resumes the command running in the next level up.  When that command finishes, you can then use C-M-c to exit another recursive editing level, and so on.  Exiting applies to the innermost level only. Aborting also gets out of only one level of recursive edit; it returns immediately to the command level of the previous recursive edit.  If you wish, you can then abort the next recursive editing level.

Alternatively, the command M-x top-level aborts all levels of recursive edits, returning immediately to the top level command reader.

The text being edited inside the recursive edit need not be the same text that you were editing at top level.  It depends on what the recursive edit is for.  If the command that invokes the recursive edit selects a different buffer first, that is the buffer you will edit recursively.  In any case, you can switch buffers within the recursive edit in the normal manner (as long as the buffer-switching keys have not been rebound).  You could probably do all the rest of your editing inside the recursive edit, visiting files and all.  But this could have surprising effects (such as stack overflow) from time to time.  So remember to exit or abort the recursive edit when you no longer need it.

In general, we try to minimize the use of recursive editing levels in GNU Emacs.  This is because they constrain you to ``go back'' in a particular order--from the innermost level toward the top level.  When possible, we present different activities in separate buffers.  Some commands switch to a new major mode but provide a way to switch back. These approaches give you more flexibility to go back to unfinished tasks in the order you choose.

Dissociated Press
=================

M-x dissociated-press is a command for scrambling a file of text either word by word or character by character.  Starting from a buffer of straight English, it produces extremely amusing output.  The input comes from the current Emacs buffer.  Dissociated Press writes its output in a buffer named *Dissociation*, and redisplays that buffer after every couple of lines (approximately) to facilitate reading it.

Dissociated Press asks every so often whether to continue operating. Answer n to stop it.  You can also stop at any time by typing C-g.  The dissociation output remains in the *Dissociation* buffer for you to copy elsewhere if you wish.

Dissociated Press operates by jumping at random from one point in the buffer to another.  In order to produce plausible output rather than gibberish, it insists on a certain amount of overlap between the end of one run of consecutive words or characters and the start of the next. That is, if it has just printed out `president' and then decides to jump to a different point in the file, it might spot the `ent' in `pentagon' and continue from there, producing `presidentagon'. (This dissociword actually appeared during the Vietnam War, when it was very appropriate.)  Long sample texts produce the best results.

A positive argument to M-x dissociated-press tells it to operate character by character, and specifies the number of overlap characters.  A negative argument tells it to operate word by word and specifies the number of overlap words.  In this mode, whole words are treated as the elements to be permuted, rather than characters.  No argument is equivalent to an argument of two.  For your againformation, the output goes only into the buffer *Dissociation*.  The buffer you start with is not changed.

Dissociated Press produces nearly the same results as a Markov chain based on a frequency table constructed from the sample text.  It is, however, an independent, ignoriginal invention.  Dissociated Press techniquitously copies several consecutive characters from the sample between random choices, whereas a Markov chain would choose randomly for each word or character.  This makes for more plausible sounding results, and runs faster.

It is a mustatement that too much use of Dissociated Press can be a developediment to your real work.  Sometimes to the point of outragedy. And keep dissociwords out of your documentation, if you want it to be well userenced and properbose.  Have fun.  Your buggestions are welcome.

Other Amusements
================

If you are a little bit bored, you can try M-x hanoi.  If you are considerably bored, give it a numeric argument.  If you are very very bored, try an argument of 9.  Sit back and watch.

If you want a little more personal involvement, try M-x gomoku, which plays the game Go Moku with you.

M-x blackbox and M-x mpuz are two kinds of puzzles. blackbox challenges you to determine the location of objects inside a box by tomography.  mpuz displays a multiplication puzzle with letters standing for digits in a code that you must guess---to guess a value, type a letter and then the digit you think it stands for.

M-x dunnet runs an adventure-style exploration game, which is a bigger sort of puzzle.

When you are frustrated, try the famous Eliza program.  Just do M-x doctor.  End each input by typing RET twice.

When you are feeling strange, type M-x yow.

Emulation
=========

GNU Emacs can be programmed to emulate (more or less) most other editors.  Standard facilities can emulate these:

EDT (DEC VMS editor)
     Turn on EDT emulation with M-x edt-emulation-on.  M-x edt-emulation-off restores normal Emacs command bindings.

     Most of the EDT emulation commands are keypad keys, and most standard Emacs key bindings are still available.  The EDT emulation rebindings are done in the global keymap, so there is no problem switching buffers or major modes while in EDT emulation.

Gosling Emacs
     To turn on emulation of Gosling Emacs (alias Unipress Emacs), type the command M-x set-gosmacs-bindings.  This redefines many keys, mostly on the C-x and ESC prefixes, to work as they do in Gosmacs.  M-x set-gnu-bindings returns to normal GNU Emacs by rebinding the same keys to the definitions they had before you used M-x set-gosmacs-bindings.

vi (Berkeley Unix editor)
     Turn on vi emulation with M-x vi-mode.  This is a major mode that replaces the previously established major mode.  All of the vi commands that, in real vi, enter ``input'' mode are programmed in the Emacs emulator to return to the previous major mode.  Thus, ordinary Emacs serves as vi's ``input'' mode.

     Because vi emulation works through major modes, it does not work to switch buffers during emulation.  Return to normal Emacs first.

     If you plan to use vi emulation much, you probably want to bind a key to the vi-mode command.

vi (alternate emulator)
     Another vi emulator said to resemble real vi more thoroughly is invoked by M-x vip-mode.  ``Input'' mode in this emulator is changed from ordinary Emacs so you can use ESC to go back to emulated vi command mode.  To get from emulated vi command mode back to ordinary Emacs, type C-z.

     This emulation does not work through major modes, and it is possible to switch buffers in various ways within the emulator.  It is not so necessary to assign a key to the command vip-mode as it is with vi-mode because terminating insert mode does not use it.

     For full information, see the long comment at the beginning of the source file, which is lisp/vip.el in the Emacs distribution.

I am interested in hearing which vi emulator users prefer, as well as in receiving more complete user documentation for either or both emulators. Warning: loading both at once may cause name conflicts; no one has checked.