@c This is part of the Emacs manual. @c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc. @c See file emacs.texi for copying conditions. @iftex @chapter Miscellaneous Commands This chapter contains several brief topics that do not fit anywhere else: reading netnews, running shell commands and shell subprocesses, using a single shared Emacs for utilities that expect to run an editor as a subprocess, printing hardcopy, sorting text, narrowing display to part of the buffer, editing double-column files and binary files, saving an Emacs session for later resumption, emulating other editors, and various diversions and amusements. @end iftex @node Gnus, Shell, Calendar/Diary, Top @section Gnus @cindex Gnus @cindex reading netnews Gnus is an Emacs package primarily designed for reading and posting Usenet news. It can also be used to read and respond to messages from a number of other sources---mail, remote directories, digests, and so on. Here we introduce Gnus and describe several basic features. @ifinfo For full details, see @ref{Top, Gnus,, gnus, The Gnus Manual}. @end ifinfo @iftex For full details on Gnus, type @kbd{M-x info} and then select the Gnus manual. @end iftex @findex gnus To start Gnus, type @kbd{M-x gnus @key{RET}}. @menu * Buffers of Gnus:: The group, summary, and article buffers. * Gnus Startup:: What you should know about starting Gnus. * Summary of Gnus:: A short description of the basic Gnus commands. @end menu @node Buffers of Gnus @subsection Gnus Buffers As opposed to most normal Emacs packages, Gnus uses a number of different buffers to display information and to receive commands. The three buffers users spend most of their time in are the @dfn{group buffer}, the @dfn{summary buffer} and the @dfn{article buffer}. The @dfn{group buffer} contains a list of groups. This is the first buffer Gnus displays when it starts up. It normally displays only the groups to which you subscribe and that contain unread articles. Use this buffer to select a specific group. The @dfn{summary buffer} lists one line for each article in a single group. By default, the author, the subject and the line number are displayed for each article, but this is customizable, like most aspects of Gnus display. The summary buffer is created when you select a group in the group buffer, and is killed when you exit the group. Use this buffer to select an article. The @dfn{article buffer} displays the article. In normal Gnus usage, you don't select this buffer---all useful article-oriented commands work in the summary buffer. But you can select the article buffer, and execute all Gnus commands from that buffer, if you want to. @node Gnus Startup @subsection When Gnus Starts Up At startup, Gnus reads your @file{.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 group buffer, type @kbd{L} or @kbd{A k} to get a listing of all the groups. Then type @kbd{u} to toggle subscription to groups. The first time you start Gnus, Gnus subscribes you to a few selected groups. All other groups start out as @dfn{killed groups} for you; you can list them with @kbd{A k}. All new groups that subsequently come to exist at the news server become @dfn{zombie groups} for you; type @kbd{A z} to list them. You can subscribe to a group shown in these lists using the @kbd{u} command. When you quit Gnus with @kbd{q}, it automatically records in your @file{.newsrc} and @file{.newsrc.eld} initialization files the subscribed or unsubscribed status of all groups. You should normally not edit these files manually, but you may if you know how. @node Summary of Gnus @subsection Summary of Gnus Commands Reading news is a two step process: @enumerate @item Choose a group in the group buffer. @item 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. @end enumerate Each Gnus buffer has its own special commands; however, the meanings of any given key in the various Gnus buffers are usually analogous, even if not identical. Here are commands for the group and summary buffers: @table @kbd @kindex q @r{(Gnus Group mode)} @findex gnus-group-exit @item q In the group buffer, update your @file{.newsrc} initialization file and quit Gnus. In the summary buffer, exit the current group and return to the group buffer. Thus, typing @kbd{q} twice quits Gnus. @kindex L @r{(Gnus Group mode)} @findex gnus-group-list-all-groups @item L In the group buffer, list all the groups available on your news server (except those you have killed). This may be a long list! @kindex l @r{(Gnus Group mode)} @findex gnus-group-list-groups @item l In the group buffer, list only the groups to which you subscribe and which contain unread articles. @kindex u @r{(Gnus Group mode)} @findex gnus-group-unsubscribe-current-group @cindex subscribe groups @cindex unsubscribe groups @item u In the group buffer, unsubscribe from (or subscribe to) the group listed in the line that point is on. When you quit Gnus by typing @kbd{q}, Gnus lists in your @file{.newsrc} file which groups you have subscribed to. The next time you start Gnus, you won't see this group, because Gnus normally displays only subscribed-to groups. @kindex C-k @r{(Gnus)} @findex gnus-group-kill-group @item C-k In the group buffer, ``kill'' the current line's group---don't even list it in @file{.newsrc} from now on. This affects future Gnus sessions as well as the present session. When you quit Gnus by typing @kbd{q}, Gnus writes information in the file @file{.newsrc} describing all newsgroups except those you have ``killed.'' @kindex SPC @r{(Gnus)} @findex gnus-group-read-group @item @key{SPC} In the group buffer, select the group on the line under the cursor and display the first unread article in that group. @need 1000 In the summary buffer, @itemize @bullet @item Select the article on the line under the cursor if none is selected. @item Scroll the text of the selected article (if there is one). @item Select the next unread article if at the end of the current article. @end itemize Thus, you can move through all the articles by repeatedly typing @key{SPC}. @kindex DEL @r{(Gnus)} @item @key{DEL} In the group buffer, move point to the previous group containing unread articles. @findex gnus-summary-prev-page In the summary buffer, scroll the text of the article backwards. @kindex n @r{(Gnus)} @findex gnus-group-next-unread-group @findex gnus-summary-next-unread-article @item n Move point to the next unread group, or select the next unread article. @kindex p @r{(Gnus)} @findex gnus-group-prev-unread-group @findex gnus-summary-prev-unread-article @item p Move point to the previous unread group, or select the previous unread article. @kindex C-n @r{(Gnus Group mode)} @findex gnus-group-next-group @kindex C-p @r{(Gnus Group mode)} @findex gnus-group-prev-group @kindex C-n @r{(Gnus Summary mode)} @findex gnus-summary-next-subject @kindex C-p @r{(Gnus Summary mode)} @findex gnus-summary-prev-subject @item C-n @itemx C-p Move point to the next or previous item, even if it is marked as read. This does not select the article or group on that line. @kindex s @r{(Gnus Summary mode)} @findex gnus-summary-isearch-article @item 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 @kbd{C-s}. @kindex M-s @r{(Gnus Summary mode)} @findex gnus-summary-search-article-forward @item M-s @var{regexp} @key{RET} In the summary buffer, search forward for articles containing a match for @var{regexp}. @end table @ignore @node Where to Look @subsection Where to Look Further @c Too many references to the name of the manual if done with xref in TeX! Gnus is powerful and customizable. Here are references to a few @ifinfo additional topics: @end ifinfo @iftex additional topics in @cite{The Gnus Manual}: @itemize @bullet @item Follow discussions on specific topics.@* See section ``Threading.'' @item Read digests. See section ``Document Groups.'' @item Refer to and jump to the parent of the current article.@* See section ``Finding the Parent.'' @item Refer to articles by using Message-IDs included in the messages.@* See section ``Article Keymap.'' @item Save articles. See section ``Saving Articles.'' @item Have Gnus score articles according to various criteria, like author name, subject, or string in the body of the articles.@* See section ``Scoring.'' @item Send an article to a newsgroup.@* See section ``Composing Messages.'' @end itemize @end iftex @ifinfo @itemize @bullet @item Follow discussions on specific topics.@* @xref{Threading, , Reading Based on Conversation Threads, gnus, The Gnus Manual}. @item Read digests. @xref{Document Groups, , , gnus, The Gnus Manual}. @item Refer to and jump to the parent of the current article.@* @xref{Finding the Parent, , , gnus, The Gnus Manual}. @item Refer to articles by using Message-IDs included in the messages.@* @xref{Article Keymap, , , gnus, The Gnus Manual}. @item Save articles. @xref{Saving Articles, , , gnus, The Gnus Manual}. @item Have Gnus score articles according to various criteria, like author name, subject, or string in the body of the articles.@* @xref{Scoring, , , gnus, The Gnus Manual}. @item Send an article to a newsgroup.@* @xref{Composing Messages, , , gnus, The Gnus Manual}. @end itemize @end ifinfo @end ignore @node Shell, Emacs Server, Gnus, Top @section Running Shell Commands from Emacs @cindex subshell @cindex shell commands 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 named @samp{*shell*}. @table @kbd @item M-! @var{cmd} @key{RET} Run the shell command line @var{cmd} and display the output (@code{shell-command}). @item M-| @var{cmd} @key{RET} Run the shell command line @var{cmd} with region contents as input; optionally replace the region with the output (@code{shell-command-on-region}). @item M-x shell Run a subshell with input and output through an Emacs buffer. You can then give commands interactively. @end table @menu * Single Shell:: How to run one shell command and return. * Interactive Shell:: Permanent shell taking input via Emacs. * Shell Mode:: Special Emacs commands used with permanent shell. * History: Shell History. Repeating previous commands in a shell buffer. * Options: Shell Options. Options for customizing Shell mode. * Remote Host:: Connecting to another computer. @end menu @node Single Shell @subsection Single Shell Commands @kindex M-! @findex shell-command @kbd{M-!} (@code{shell-command}) reads a line of text using the minibuffer and executes it as a shell command in a subshell made just for that 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 @samp{*Shell Command Output*}, which is displayed in another window but not selected. A numeric argument, as in @kbd{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 @samp{&}, it runs asynchronously. For a synchronous shell command, @code{shell-command} returns the command's exit status (0 means success), when it is called from a Lisp program. @kindex M-| @findex shell-command-on-region @kbd{M-|} (@code{shell-command-on-region}) is like @kbd{M-!} but passes the contents of the region as the standard input to the shell command, instead of no input. If a numeric argument is used, meaning insert the output in the current buffer, then the old region is deleted first and the output replaces it as the contents of the region. It returns the command's exit status when it is called from a Lisp program. @vindex shell-file-name @cindex environment Both @kbd{M-!} and @kbd{M-|} use @code{shell-file-name} to specify the shell to use. This variable is initialized based on your @code{SHELL} environment variable when Emacs is started. If the file name does not specify a directory, the directories in the list @code{exec-path} are searched; this list is initialized based on the environment variable @code{PATH} when Emacs is started. Your @file{.emacs} file can override either or both of these default initializations.@refill Both @kbd{M-!} and @kbd{M-|} wait for the shell command to complete. To stop waiting, type @kbd{C-g} to quit; that terminates the shell command with the signal @code{SIGINT}---the same signal that @kbd{C-c} normally generates in the shell. Emacs waits until the command actually terminates. If the shell command doesn't stop (because it ignores the @code{SIGINT} signal), type @kbd{C-g} again; this sends the command a @code{SIGKILL} signal which is impossible to ignore. To specify a coding system for @kbd{M-!} or @kbd{M-|}, use the command @kbd{C-x @key{RET} c} immediately beforehand. @xref{Specify Coding}. @vindex shell-command-default-error-buffer Error output from the command is normally intermixed with the regular output. If you set the variable @code{shell-command-default-error-buffer} to a string, which is a buffer name, error output is inserted before point in the buffer of that name. @node Interactive Shell @subsection Interactive Inferior Shell @findex shell To run a subshell interactively, putting its typescript in an Emacs buffer, use @kbd{M-x shell}. This creates (or reuses) a buffer named @samp{*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 @key{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 @samp{*shell*} to something different using @kbd{M-x rename-uniquely}. Then type @kbd{M-x shell} again to create a new buffer @samp{*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. @vindex explicit-shell-file-name @cindex @code{ESHELL} environment variable @cindex @code{SHELL} environment variable The file name used to load the subshell is the value of the variable @code{explicit-shell-file-name}, if that is non-@code{nil}. Otherwise, the environment variable @code{ESHELL} is used, or the environment variable @code{SHELL} if there is no @code{ESHELL}. If the file name specified is relative, the directories in the list @code{exec-path} are searched; this list is initialized based on the environment variable @code{PATH} when Emacs is started. Your @file{.emacs} file can override either or both of these default initializations. To specify a coding system for the shell, you can use the command @kbd{C-x @key{RET} c} immediately before @kbd{M-x shell}. You can also specify a coding system after starting the shell by using @kbd{C-x @key{RET} p} in the shell buffer. @xref{Specify Coding}. As soon as the subshell is started, it is sent as input the contents of the file @file{~/.emacs_@var{shellname}}, if that file exists, where @var{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 @file{~/.emacs_bash}. @vindex shell-pushd-regexp @vindex shell-popd-regexp @vindex shell-cd-regexp @code{cd}, @code{pushd} and @code{popd} commands given to the inferior shell are watched by Emacs so it can keep the @samp{*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 @code{shell-pushd-regexp} matches the beginning of a shell command line, that line is regarded as a @code{pushd} command. Change this variable when you add aliases for @samp{pushd}. Likewise, @code{shell-popd-regexp} and @code{shell-cd-regexp} are used to recognize commands with the meaning of @samp{popd} and @samp{cd}. These commands are recognized only at the beginning of a shell command line.@refill @vindex shell-set-directory-error-hook If Emacs gets an error while trying to handle what it believes is a @samp{cd}, @samp{pushd} or @samp{popd} command, it runs the hook @code{shell-set-directory-error-hook} (@pxref{Hooks}). @findex dirs If Emacs does not properly track changes in the current directory of the subshell, use the command @kbd{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. @findex dirtrack-mode You can also use @kbd{M-x dirtrack-mode} to enable (or disable) an alternative and more aggressive method of tracking changes in the current directory. Emacs defines the environment variable @code{EMACS} in the subshell, with value @code{t}. A shell script can check this variable to determine whether it has been run from an Emacs subshell. @node Shell Mode @subsection Shell Mode @cindex Shell mode @cindex mode, Shell Shell buffers use Shell mode, which defines several special keys attached to the @kbd{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 @kbd{C-c} first. Here is a complete list of the special key bindings of Shell mode: @table @kbd @item @key{RET} @kindex RET @r{(Shell mode)} @findex comint-send-input At end of buffer send line as input; otherwise, copy current line to end of buffer and send it (@code{comint-send-input}). When a line is copied, any text at the beginning of the line that matches the variable @code{shell-prompt-pattern} is left out; this variable's value should be a regexp string that matches the prompts that your shell uses. @item @key{TAB} @kindex TAB @r{(Shell mode)} @findex comint-dynamic-complete Complete the command name or file name before point in the shell buffer (@code{comint-dynamic-complete}). @key{TAB} also completes history references (@pxref{History References}) and environment variable names. @vindex shell-completion-fignore @vindex comint-completion-fignore The variable @code{shell-completion-fignore} specifies a list of file name extensions to ignore in Shell mode completion. The default setting ignores file names ending in @samp{~}, @samp{#} or @samp{%}. Other related Comint modes use the variable @code{comint-completion-fignore} instead. @item M-? @kindex M-? @r{(Shell mode)} @findex comint-dynamic-list-filename@dots{} Display temporarily a list of the possible completions of the file name before point in the shell buffer (@code{comint-dynamic-list-filename-completions}). @item C-d @kindex C-d @r{(Shell mode)} @findex comint-delchar-or-maybe-eof Either delete a character or send @sc{eof} (@code{comint-delchar-or-maybe-eof}). Typed at the end of the shell buffer, @kbd{C-d} sends @sc{eof} to the subshell. Typed at any other position in the buffer, @kbd{C-d} deletes a character as usual. @item C-c C-a @kindex C-c C-a @r{(Shell mode)} @findex comint-bol Move to the beginning of the line, but after the prompt if any (@code{comint-bol}). If you repeat this command twice in a row, the second time it moves back to the process mark, which is the beginning of the input that you have not yet sent to the subshell. (Normally that is the same place---the end of the prompt on this line---but after @kbd{C-c @key{SPC}} the process mark may be in a previous line.) @item C-c @key{SPC} Accumulate multiple lines of input, then send them together. This command inserts a newline before point, but does not send the preceding text as input to the subshell---at least, not yet. Both lines, the one before this newline and the one after, will be sent together (along with the newline that separates them), when you type @key{RET}. @item C-c C-u @kindex C-c C-u @r{(Shell mode)} @findex comint-kill-input Kill all text pending at end of buffer to be sent as input (@code{comint-kill-input}). @item C-c C-w @kindex C-c C-w @r{(Shell mode)} Kill a word before point (@code{backward-kill-word}). @item C-c C-c @kindex C-c C-c @r{(Shell mode)} @findex comint-interrupt-subjob Interrupt the shell or its current subjob if any (@code{comint-interrupt-subjob}). This command also kills any shell input pending in the shell buffer and not yet sent. @item C-c C-z @kindex C-c C-z @r{(Shell mode)} @findex comint-stop-subjob Stop the shell or its current subjob if any (@code{comint-stop-subjob}). This command also kills any shell input pending in the shell buffer and not yet sent. @item C-c C-\ @findex comint-quit-subjob @kindex C-c C-\ @r{(Shell mode)} Send quit signal to the shell or its current subjob if any (@code{comint-quit-subjob}). This command also kills any shell input pending in the shell buffer and not yet sent. @item C-c C-o @kindex C-c C-o @r{(Shell mode)} @findex comint-kill-output Kill the last batch of output from a shell command (@code{comint-kill-output}). This is useful if a shell command spews out lots of output that just gets in the way. @item C-c C-r @itemx C-M-l @kindex C-c C-r @r{(Shell mode)} @kindex C-M-l @r{(Shell mode)} @findex comint-show-output Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (@code{comint-show-output}). @item C-c C-e @kindex C-c C-e @r{(Shell mode)} @findex comint-show-maximum-output Scroll to put the end of the buffer at the bottom of the window (@code{comint-show-maximum-output}). @item C-c C-f @kindex C-c C-f @r{(Shell mode)} @findex shell-forward-command @vindex shell-command-regexp Move forward across one shell command, but not beyond the current line (@code{shell-forward-command}). The variable @code{shell-command-regexp} specifies how to recognize the end of a command. @item C-c C-b @kindex C-c C-b @r{(Shell mode)} @findex shell-backward-command Move backward across one shell command, but not beyond the current line (@code{shell-backward-command}). @item C-c C-l @kindex C-c C-l @r{(Shell mode)} @findex comint-dynamic-list-input-ring Display the buffer's history of shell commands in another window (@code{comint-dynamic-list-input-ring}). @item M-x dirs Ask the shell what its current directory is, so that Emacs can agree with the shell. @item M-x send-invisible @key{RET} @var{text} @key{RET} @findex send-invisible Send @var{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. Alternatively, you can arrange for Emacs to notice password prompts and turn off echoing for them, as follows: @example (add-hook 'comint-output-filter-functions 'comint-watch-for-password-prompt) @end example @item M-x comint-continue-subjob @findex comint-continue-subjob Continue the shell process. This is useful if you accidentally suspend the shell process.@footnote{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.} @item M-x comint-strip-ctrl-m @findex comint-strip-ctrl-m Discard all control-M characters from the current group of shell output. The most convenient way to use this command is to make it run automatically when you get output from the subshell. To do that, evaluate this Lisp expression: @example (add-hook 'comint-output-filter-functions 'comint-strip-ctrl-m) @end example @item M-x comint-truncate-buffer @findex comint-truncate-buffer This command truncates the shell buffer to a certain maximum number of lines, specified by the variable @code{comint-buffer-maximum-size}. Here's how to do this automatically each time you get output from the subshell: @example (add-hook 'comint-output-filter-functions 'comint-truncate-buffer) @end example @end table Shell mode also customizes the paragraph commands so that only shell prompts start new paragraphs. Thus, a paragraph consists of an input command plus the output that follows it in the buffer. @cindex Comint mode @cindex mode, Comint Shell mode is a derivative of Comint mode, a general-purpose mode for communicating with interactive subprocesses. Most of the features of Shell mode actually come from Comint mode, as you can see from the command names listed above. The special features of Shell mode in particular include the choice of regular expression for detecting prompts, the directory tracking feature, and a few user commands. Other Emacs features that use variants of Comint mode include GUD (@pxref{Debuggers}) and @kbd{M-x run-lisp} (@pxref{External Lisp}). @findex comint-run You can use @kbd{M-x comint-run} to execute any program of your choice in a subprocess using unmodified Comint mode---without the specializations of Shell mode. @node Shell History @subsection Shell Command History Shell buffers support three ways of repeating earlier commands. You can use the same keys used in the minibuffer; these work much as they do in the minibuffer, inserting text from prior commands while point remains always at the end of the buffer. You can move through the buffer to previous inputs in their original place, then resubmit them or copy them to the end. Or you can use a @samp{!}-style history reference. @menu * Ring: Shell Ring. Fetching commands from the history list. * Copy: Shell History Copying. Moving to a command and then copying it. * History References:: Expanding @samp{!}-style history references. @end menu @node Shell Ring @subsubsection Shell History Ring @table @kbd @findex comint-previous-input @kindex M-p @r{(Shell mode)} @item M-p Fetch the next earlier old shell command. @kindex M-n @r{(Shell mode)} @findex comint-next-input @item M-n Fetch the next later old shell command. @kindex M-r @r{(Shell mode)} @kindex M-s @r{(Shell mode)} @findex comint-previous-matching-input @findex comint-next-matching-input @item M-r @var{regexp} @key{RET} @itemx M-s @var{regexp} @key{RET} Search backwards or forwards for old shell commands that match @var{regexp}. @item C-c C-x @r{(Shell mode)} @findex comint-get-next-from-history Fetch the next subsequent command from the history. @end table Shell buffers provide a history of previously entered shell commands. To reuse shell commands from the history, use the editing commands @kbd{M-p}, @kbd{M-n}, @kbd{M-r} and @kbd{M-s}. These work just like the minibuffer history commands except that they operate on the text at the end of the shell buffer, where you would normally insert text to send to the shell. @kbd{M-p} fetches an earlier shell command to the end of the shell buffer. Successive use of @kbd{M-p} fetches successively earlier shell commands, each replacing any text that was already present as potential shell input. @kbd{M-n} does likewise except that it finds successively more recent shell commands from the buffer. The history search commands @kbd{M-r} and @kbd{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 @kbd{M-p} and @kbd{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 @key{RET}, or you can edit it first and then resubmit it if you wish. Often it is useful to reexecute several successive shell commands that were previously executed in sequence. To do this, first find and reexecute the first command of the sequence. Then type @kbd{C-c C-x}; that will fetch the following command---the one that follows the command you just repeated. Then type @key{RET} to reexecute this command. You can reexecute several successive commands by typing @kbd{C-c C-x @key{RET}} over and over. 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. @vindex shell-input-ring-file-name Some shells store their command histories in files so that you can refer to previous commands from previous shell sessions. Emacs reads the command history file for your chosen shell, to initialize its own command history. The file name is @file{~/.bash_history} for bash, @file{~/.sh_history} for ksh, and @file{~/.history} for other shells. @node Shell History Copying @subsubsection Shell History Copying @table @kbd @kindex C-c C-p @r{(Shell mode)} @findex comint-previous-prompt @item C-c C-p Move point to the previous prompt (@code{comint-previous-prompt}). @kindex C-c C-n @r{(Shell mode)} @findex comint-next-prompt @item C-c C-n Move point to the following prompt (@code{comint-next-prompt}). @kindex C-c RET @r{(Shell mode)} @findex comint-copy-old-input @item C-c @key{RET} Copy the input command which point is in, inserting the copy at the end of the buffer (@code{comint-copy-old-input}). This is useful if you move point back to a previous command. After you copy the command, you can submit the copy as input with @key{RET}. If you wish, you can edit the copy before resubmitting it. @end table Moving to a previous input and then copying it with @kbd{C-c @key{RET}} produces the same results---the same buffer contents---that you would get by using @kbd{M-p} enough times to fetch that previous input from the history list. However, @kbd{C-c @key{RET}} copies the text from the buffer, which can be different from what is in the history list if you edit the input text in the buffer after it has been sent. @node History References @subsubsection Shell History References @cindex history reference Various shells including csh and bash support @dfn{history references} that begin with @samp{!} and @samp{^}. Shell mode can understand these constructs and perform the history substitution for you. If you insert a history reference and type @key{TAB}, this searches the input history for a matching command, performs substitution if necessary, and places the result in the buffer in place of the history reference. For example, you can fetch the most recent command beginning with @samp{mv} with @kbd{! m v @key{TAB}}. You can edit the command if you wish, and then resubmit the command to the shell by typing @key{RET}. @vindex shell-prompt-pattern @vindex comint-prompt-regexp History references take effect only following a shell prompt. The variable @code{shell-prompt-pattern} specifies how to recognize a shell prompt. Comint modes in general use the variable @code{comint-prompt-regexp} to specify how to find a prompt; Shell mode uses @code{shell-prompt-pattern} to set up the local value of @code{comint-prompt-regexp}. @vindex comint-input-autoexpand Shell mode can optionally expand history references in the buffer when you send them to the shell. To request this, set the variable @code{comint-input-autoexpand} to @code{input}. @findex comint-magic-space You can make @key{SPC} perform history expansion by binding @key{SPC} to the command @code{comint-magic-space}. @node Shell Options @subsection Shell Mode Options @vindex comint-scroll-to-bottom-on-input If the variable @code{comint-scroll-to-bottom-on-input} is non-@code{nil}, insertion and yank commands scroll the selected window to the bottom before inserting. @vindex comint-scroll-show-maximum-output If @code{comint-scroll-show-maximum-output} is non-@code{nil}, then scrolling due to arrival of output tries to place the last line of text at the bottom line of the window, so as to show as much useful text as possible. (This mimics the scrolling behavior of many terminals.) The default is @code{nil}. @vindex comint-scroll-to-bottom-on-output By setting @code{comint-scroll-to-bottom-on-output}, you can opt for having point jump to the end of the buffer whenever output arrives---no matter where in the buffer point was before. If the value is @code{this}, point jumps in the selected window. If the value is @code{all}, point jumps in each window that shows the comint buffer. If the value is @code{other}, point jumps in all nonselected windows that show the current buffer. The default value is @code{nil}, which means point does not jump to the end. @vindex comint-input-ignoredups The variable @code{comint-input-ignoredups} controls whether successive identical inputs are stored in the input history. A non-@code{nil} value means to omit an input that is the same as the previous input. The default is @code{nil}, which means to store each input even if it is equal to the previous input. @vindex comint-completion-addsuffix @vindex comint-completion-recexact @vindex comint-completion-autolist Three variables customize file name completion. The variable @code{comint-completion-addsuffix} controls whether completion inserts a space or a slash to indicate a fully completed file or directory name (non-@code{nil} means do insert a space or slash). @code{comint-completion-recexact}, if non-@code{nil}, directs @key{TAB} to choose the shortest possible completion if the usual Emacs completion algorithm cannot add even a single character. @code{comint-completion-autolist}, if non-@code{nil}, says to list all the possible completions whenever completion is not exact. @findex comint-dynamic-complete-variable The command @code{comint-dynamic-complete-variable} does variable-name completion using the environment variables as set within Emacs. The variables controlling file name completion apply to variable-name completion too. This command is normally available through the menu bar. @vindex shell-command-execonly Command completion normally considers only executable files. If you set @code{shell-command-execonly} to @code{nil}, it considers nonexecutable files as well. @findex shell-pushd-tohome @findex shell-pushd-dextract @findex shell-pushd-dunique You can configure the behavior of @samp{pushd}. Variables control whether @samp{pushd} behaves like @samp{cd} if no argument is given (@code{shell-pushd-tohome}), pop rather than rotate with a numeric argument (@code{shell-pushd-dextract}), and only add directories to the directory stack if they are not already on it (@code{shell-pushd-dunique}). The values you choose should match the underlying shell, of course. @node Remote Host @subsection Remote Host Shell @cindex remote host @cindex connecting to remote host @cindex Telnet @cindex Rlogin Emacs provides two commands for logging in to another computer and communicating with it through an Emacs buffer. @table @kbd @item M-x telnet @key{RET} @var{hostname} @key{RET} Set up a Telnet connection to the computer named @var{hostname}. @item M-x rlogin @key{RET} @var{hostname} @key{RET} Set up an Rlogin connection to the computer named @var{hostname}. @end table @findex telnet Use @kbd{M-x telnet} to set up a Telnet connection to another computer. (Telnet is the standard Internet protocol for remote login.) It reads the host name of the other computer as an argument with the minibuffer. Once the connection is established, talking to the other computer works like talking to a subshell: you can edit input with the usual Emacs commands, and send it a line at a time by typing @key{RET}. The output is inserted in the Telnet buffer interspersed with the input. @findex rlogin @vindex rlogin-explicit-args Use @kbd{M-x rlogin} to set up an Rlogin connection. Rlogin is another remote login communication protocol, essentially much like the Telnet protocol but incompatible with it, and supported only by certain systems. Rlogin's advantages are that you can arrange not to have to give your user name and password when communicating between two machines you frequently use, and that you can make an 8-bit-clean connection. (To do that in Emacs, set @code{rlogin-explicit-args} to @code{("-8")} before you run Rlogin.) @kbd{M-x rlogin} sets up the default file directory of the Emacs buffer to access the remote host via FTP (@pxref{File Names}), and it tracks the shell commands that change the current directory, just like Shell mode. @findex rlogin-directory-tracking-mode There are two ways of doing directory tracking in an Rlogin buffer---either with remote directory names @file{/@var{host}:@var{dir}/} or with local names (that works if the ``remote'' machine shares file systems with your machine of origin). You can use the command @code{rlogin-directory-tracking-mode} to switch modes. No argument means use remote directory names, a positive argument means use local names, and a negative argument means turn off directory tracking. @node Emacs Server, Hardcopy, Shell, Top @section Using Emacs as a Server @pindex emacsclient @cindex Emacs as a server @cindex server, using Emacs as @cindex @code{EDITOR} environment variable Various programs such as @code{mail} can invoke your choice of editor to edit a particular piece of text, such as a message that you are sending. By convention, most of these programs use the environment variable @code{EDITOR} to specify which editor to run. If you set @code{EDITOR} to @samp{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 @code{mail} by using the Emacs client and Emacs server programs. Here is how. @cindex @code{TEXEDIT} environment variable First, the preparation. Within Emacs, call the function @code{server-start}. (Your @file{.emacs} file can do this automatically if you add the expression @code{(server-start)} to it.) Then, outside Emacs, set the @code{EDITOR} environment variable to @samp{emacsclient}. (Note that some programs use a different environment variable; for example, to make @TeX{} use @samp{emacsclient}, you should set the @code{TEXEDIT} environment variable to @samp{emacsclient +%d %s}.) @kindex C-x # @findex server-edit Then, whenever any program invokes your specified @code{EDITOR} program, the effect is to send a message to your principal Emacs telling it to visit a file. (That's what the program @code{emacsclient} does.) Emacs displays the buffer immediately and you can immediately begin editing it. When you've finished editing that buffer, type @kbd{C-x #} (@code{server-edit}). This saves the file and sends a message back to the @code{emacsclient} program telling it to exit. The programs that use @code{EDITOR} wait for the ``editor'' (actually, @code{emacsclient}) to exit. @kbd{C-x #} also checks for other pending external requests to edit various files, and selects the next such file. You can switch to a server buffer manually if you wish; you don't have to arrive at it with @kbd{C-x #}. But @kbd{C-x #} is the only way to say that you are ``finished'' with one. @vindex server-window If you set the variable @code{server-window} to a window or a frame, @kbd{C-x #} displays the server buffer in that window or in that frame. While @code{mail} or another application is waiting for @code{emacsclient} to finish, @code{emacsclient} does not read terminal input. So the terminal that @code{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: @itemize @bullet @item Using a window system, run @code{mail} and the principal Emacs in two separate windows. While @code{mail} is waiting for @code{emacsclient}, the window where it was running is blocked, but you can use Emacs by switching windows. @item Use Shell mode in Emacs to run the other program such as @code{mail}; then, @code{emacsclient} blocks only the subshell under Emacs, and you can still use Emacs to edit the file. @end itemize @vindex server-temp-file-regexp 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 @code{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. If you run @code{emacsclient} with the option @samp{--no-wait}, it returns immediately without waiting for you to ``finish'' the buffer in Emacs. @node Hardcopy, Postscript, Emacs Server, Top @section Hardcopy Output @cindex hardcopy 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 (@pxref{Misc File Ops}) and the diary (@pxref{Diary Commands}). @table @kbd @item M-x print-buffer Print hardcopy of current buffer with page headings containing the file name and page number. @item M-x lpr-buffer Print hardcopy of current buffer without page headings. @item M-x print-region Like @code{print-buffer} but print only the current region. @item M-x lpr-region Like @code{lpr-buffer} but print only the current region. @end table @findex print-buffer @findex print-region @findex lpr-buffer @findex lpr-region @vindex lpr-switches The hardcopy commands (aside from the Postscript commands) pass extra switches to the @code{lpr} program based on the value of the variable @code{lpr-switches}. Its value should be a list of strings, each string an option starting with @samp{-}. For example, to specify a line width of 80 columns for all the printing you do in Emacs, set @code{lpr-switches} like this: @example (setq lpr-switches '("-w80")) @end example @vindex printer-name You can specify the printer to use by setting the variable @code{printer-name}. @vindex lpr-headers-switches @vindex lpr-commands @vindex lpr-add-switches The variable @code{lpr-command} specifies the name of the printer program to run; the default value depends on your operating system type. On most systems, the default is @code{"lpr"}. The variable @code{lpr-headers-switches} similarly specifies the extra switches to use to make page headers. The variable @code{lpr-add-switches} controls whether to supply @samp{-T} and @samp{-J} options (suitable for @code{lpr}) to the printer program: @code{nil} means don't add them. @code{lpr-add-switches} should be @code{nil} if your printer program is not compatible with @code{lpr}. @node Postscript, Postscript Variables, Hardcopy, Top @section Postscript Hardcopy These commands convert buffer contents to Postscript, either printing it or leaving it in another Emacs buffer. @table @kbd @item M-x ps-print-buffer Print hardcopy of the current buffer in Postscript form. @item M-x ps-print-region Print hardcopy of the current region in Postscript form. @item M-x ps-print-buffer-with-faces Print hardcopy of the current buffer in Postscript form, showing the faces used in the text by means of Postscript features. @item M-x ps-print-region-with-faces Print hardcopy of the current region in Postscript form, showing the faces used in the text. @item M-x ps-spool-buffer Generate Postscript for the current buffer text. @item M-x ps-spool-region Generate Postscript for the current region. @item M-x ps-spool-buffer-with-faces Generate Postscript for the current buffer, showing the faces used. @item M-x ps-spool-region-with-faces Generate Postscript for the current region, showing the faces used. @end table @findex ps-print-region @findex ps-print-buffer @findex ps-print-region-with-faces @findex ps-print-buffer-with-faces The Postscript commands, @code{ps-print-buffer} and @code{ps-print-region}, print buffer contents in Postscript form. One command prints the entire buffer; the other, just the region. The corresponding @samp{-with-faces} commands, @code{ps-print-buffer-with-faces} and @code{ps-print-region-with-faces}, use Postscript features to show the faces (fonts and colors) in the text properties of the text being printed. If you are using a color display, you can print a buffer of program code with color highlighting by turning on Font-Lock mode in that buffer, and using @code{ps-print-buffer-with-faces}. @findex ps-spool-region @findex ps-spool-buffer @findex ps-spool-region-with-faces @findex ps-spool-buffer-with-faces The commands whose names have @samp{spool} instead of @samp{print} generate the Postscript output in an Emacs buffer instead of sending it to the printer. @ifinfo The following section describes variables for customizing these commands. @end ifinfo @node Postscript Variables, Sorting, Postscript, Top @section Variables for Postscript Hardcopy @vindex ps-lpr-command @vindex ps-lpr-switches @vindex ps-printer-name All the Postscript hardcopy commands use the variables @code{ps-lpr-command} and @code{ps-lpr-switches} to specify how to print the output. @code{ps-lpr-command} specifies the command name to run, @code{ps-lpr-switches} specifies command line options to use, and @code{ps-printer-name} specifies the printer. If you don't set the first two variables yourself, they take their initial values from @code{lpr-command} and @code{lpr-switches}. If @code{ps-printer-name} is @code{nil}, @code{printer-name} is used. @vindex ps-print-header @vindex ps-print-color-p The variable @code{ps-print-header} controls whether these commands add header lines to each page---set it to @code{nil} to turn headers off. You can turn off color processing by setting @code{ps-print-color-p} to @code{nil}. @vindex ps-paper-type @vindex ps-page-dimensions-database The variable @code{ps-paper-type} specifies which size of paper to format for; legitimate values include @code{a4}, @code{a3}, @code{a4small}, @code{b4}, @code{b5}, @code{executive}, @code{ledger}, @code{legal}, @code{letter}, @code{letter-small}, @code{statement}, @code{tabloid}. The default is @code{letter}. You can define additional paper sizes by changing the variable @code{ps-page-dimensions-database}. @vindex ps-landscape-mode The variable @code{ps-landscape-mode} specifies the orientation of printing on the page. The default is @code{nil}, which stands for ``portrait'' mode. Any non-@code{nil} value specifies ``landscape'' mode. @vindex ps-number-of-columns The variable @code{ps-number-of-columns} specifies the number of columns; it takes effect in both landscape and portrait mode. The default is 1. @vindex ps-font-family @vindex ps-font-size @vindex ps-font-info-database The variable @code{ps-font-family} specifies which font family to use for printing ordinary text. Legitimate values include @code{Courier}, @code{Helvetica}, @code{NewCenturySchlbk}, @code{Palatino} and @code{Times}. The variable @code{ps-font-size} specifies the size of the font for ordinary text. It defaults to 8.5 points. Many other customization variables for these commands are defined and described in the Lisp file @file{ps-print.el}. @node Sorting, Narrowing, Postscript Variables, Top @section Sorting Text @cindex sorting 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 @dfn{sort records}, identify a @dfn{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. @findex sort-lines @findex sort-paragraphs @findex sort-pages @findex sort-fields @findex sort-numeric-fields @table @kbd @item M-x sort-lines Divide the region into lines, and sort by comparing the entire text of a line. A numeric argument means sort into descending order. @item 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 numeric argument means sort into descending order. @item 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 numeric argument means sort into descending order. @item 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 count fields from the right instead of from the left; thus, minus 1 means sort by the last field. If several lines have identical contents in the field being sorted, they keep same relative order that they had in the original buffer. @item M-x sort-numeric-fields Like @kbd{M-x sort-fields} except the specified field is converted to an integer for each line, and the numbers are compared. @samp{10} comes before @samp{2} when considered as text, but after it when considered as a number. @item M-x sort-columns Like @kbd{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. @item M-x reverse-region Reverse the order of the lines in the region. This is useful for sorting into descending order by fields or columns, since those sort commands do not have a feature for doing that. @end table For example, if the buffer contains this: @smallexample 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. @end smallexample @noindent applying @kbd{M-x sort-lines} to the entire buffer produces this: @smallexample 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 @end smallexample @noindent where the upper-case @samp{O} sorts before all lower-case letters. If you use @kbd{C-u 2 M-x sort-fields} instead, you get this: @smallexample 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 @end smallexample @noindent where the sort keys were @samp{Emacs}, @samp{If}, @samp{buffer}, @samp{systems} and @samp{the}. @findex sort-columns @kbd{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 of the text you want 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, as well as all the lines in between. 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 @code{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. @xref{Rectangles}. @vindex sort-fold-case Many of the sort commands ignore case differences when comparing, if @code{sort-fold-case} is non-@code{nil}. @node Narrowing, Two-Column, Sorting, Top @section Narrowing @cindex widening @cindex restriction @cindex narrowing @cindex accessible portion @dfn{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 @dfn{accessible portion}. Canceling the narrowing, which makes the entire buffer once again accessible, is called @dfn{widening}. The amount of narrowing in effect in a buffer at any time is called the buffer's @dfn{restriction}. Narrowing can make it easier to concentrate on a single subroutine or paragraph by eliminating clutter. It can also be used to restrict the range of operation of a replace command or repeating keyboard macro. @c WideCommands @table @kbd @item C-x n n Narrow down to between point and mark (@code{narrow-to-region}). @item C-x n w Widen to make the entire buffer accessible again (@code{widen}). @item C-x n p Narrow down to the current page (@code{narrow-to-page}). @item C-x n d Narrow down to the current defun (@code{narrow-to-defun}). @end table 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. The word @samp{Narrow} appears in the mode line whenever narrowing is in effect. @kindex C-x n n @findex narrow-to-region The primary narrowing command is @kbd{C-x n n} (@code{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 inaccessible. Point and mark do not change. @kindex C-x n p @findex narrow-to-page @kindex C-x n d @findex narrow-to-defun Alternatively, use @kbd{C-x n p} (@code{narrow-to-page}) to narrow down to the current page. @xref{Pages}, for the definition of a page. @kbd{C-x n d} (@code{narrow-to-defun}) narrows down to the defun containing point (@pxref{Defuns}). @kindex C-x n w @findex widen The way to cancel narrowing is to widen with @kbd{C-x n w} (@code{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 @kbd{C-x =} command. @xref{Position Info}. Because narrowing can easily confuse users who do not understand it, @code{narrow-to-region} is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; if you enable the command, confirmation will no longer be required for it. @xref{Disabling}. @node Two-Column, Editing Binary Files, Narrowing, Top @section Two-Column Editing @cindex two-column editing @cindex splitting columns @cindex columns, splitting 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: @table @asis @item @kbd{@key{F2} 2} or @kbd{C-x 6 2} @kindex F2 2 @kindex C-x 6 2 @findex 2C-two-columns 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 (@code{2C-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 is empty or contains just one column and you want to add another column. @item @kbd{@key{F2} s} or @kbd{C-x 6 s} @kindex F2 s @kindex C-x 6 s @findex 2C-split Split the current buffer, which contains two-column text, into two buffers, and display them side by side (@code{2C-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. @item @kbd{@key{F2} b @var{buffer} @key{RET}} @itemx @kbd{C-x 6 b @var{buffer} @key{RET}} @kindex F2 b @kindex C-x 6 b @findex 2C-associate-buffer Enter two-column mode using the current buffer as the left-hand buffer, and using buffer @var{buffer} as the right-hand buffer (@code{2C-associate-buffer}). @end table @kbd{@key{F2} s} or @kbd{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 @kbd{@key{F2} 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, @kbd{@key{F2} 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 that ``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.) @kindex F2 RET @kindex C-x 6 RET @findex 2C-newline The command @kbd{C-x 6 @key{RET}} or @kbd{@key{F2} @key{RET}} (@code{2C-newline}) inserts a newline in each of the two buffers at corresponding positions. This is the easiest way to add a new line to the two-column text while editing it in split buffers. @kindex F2 1 @kindex C-x 6 1 @findex 2C-merge When you have edited both buffers as you wish, merge them with @kbd{@key{F2} 1} or @kbd{C-x 6 1} (@code{2C-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 @kbd{@key{F2} s}. @kindex F2 d @kindex C-x 6 d @findex 2C-dissociate Use @kbd{@key{F2} d} or @kbd{C-x 6 d} to dissociate the two buffers, leaving each as it stands (@code{2C-dissociate}). If the other buffer, the one not current when you type @kbd{@key{F2} d}, is empty, @kbd{@key{F2} d} kills it. @node Editing Binary Files, Saving Emacs Sessions, Two-Column, Top @section Editing Binary Files @cindex Hexl mode @cindex mode, Hexl @cindex editing binary files There is a special major mode for editing binary files: Hexl mode. To use it, use @kbd{M-x hexl-find-file} instead of @kbd{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 @kbd{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 I don't think individual index entries for these commands are useful--RMS. @table @kbd @item C-M-d Insert a byte with a code typed in decimal. @item C-M-o Insert a byte with a code typed in octal. @item C-M-x Insert a byte with a code typed in hex. @item C-x [ Move to the beginning of a 1k-byte ``page.'' @item C-x ] Move to the end of a 1k-byte ``page.'' @item M-g Move to an address specified in hex. @item M-j Move to an address specified in decimal. @item C-c C-c Leave Hexl mode, going back to the major mode this buffer had before you invoked @code{hexl-mode}. @end table @node Saving Emacs Sessions, Recursive Edit, Editing Binary Files, Top @section Saving Emacs Sessions @cindex saving sessions @cindex desktop You can use the Desktop library to save the state of Emacs from one session to another. Saving the state means that Emacs starts up with the same set of buffers, major modes, buffer positions, and so on that the previous Emacs session had. @vindex desktop-enable To use Desktop, you should use the Customization buffer (@pxref{Easy Customization}) to set @code{desktop-enable} to a non-@code{nil} value, or add these lines at the end of your @file{.emacs} file: @example (desktop-load-default) (desktop-read) @end example @noindent @findex desktop-save The first time you save the state of the Emacs session, you must do it manually, with the command @kbd{M-x desktop-save}. Once you have done that, exiting Emacs will save the state again---not only the present Emacs session, but also subsequent sessions. You can also save the state at any time, without exiting Emacs, by typing @kbd{M-x desktop-save} again. In order for Emacs to recover the state from a previous session, you must start it with the same current directory as you used when you started the previous session. This is because @code{desktop-read} looks in the current directory for the file to read. This means that you can have separate saved sessions in different directories; the directory in which you start Emacs will control which saved session to use. @vindex desktop-files-not-to-save The variable @code{desktop-files-not-to-save} controls which files are excluded from state saving. Its value is a regular expression that matches the files to exclude. By default, remote (ftp-accessed) files are excluded; this is because visiting them again in the subsequent session would be slow. If you want to include these files in state saving, set @code{desktop-files-not-to-save} to @code{"^$"}. @xref{Remote Files}. @node Recursive Edit, Emulation, Saving Emacs Sessions, Top @section Recursive Editing Levels @cindex recursive editing level @cindex editing level, recursive A @dfn{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 @kbd{C-r} inside of a @code{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 @code{query-replace}. @kindex C-M-c @findex exit-recursive-edit @cindex exiting recursive edit @dfn{Exiting} the recursive edit means returning to the unfinished command, which continues execution. The command to exit is @kbd{C-M-c} (@code{exit-recursive-edit}). You can also @dfn{abort} the recursive edit. This is like exiting, but also quits the unfinished command immediately. Use the command @kbd{C-]} (@code{abort-recursive-edit}) to do this. @xref{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 @kbd{C-r} in a @code{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 @kbd{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 @kbd{c} command) resumes the command running in the next level up. When that command finishes, you can then use @kbd{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 @kbd{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 so that you can switch between them as you please. Some commands switch to a new major mode which provides a command to switch back. These approaches give you more flexibility to go back to unfinished tasks in the order you choose. @node Emulation, Dissociated Press, Recursive Edit, Top @section Emulation @cindex emulating other editors @cindex other editors @cindex EDT @cindex vi GNU Emacs can be programmed to emulate (more or less) most other editors. Standard facilities can emulate these: @table @asis @item EDT (DEC VMS editor) @findex edt-emulation-on @findex edt-emulation-off Turn on EDT emulation with @kbd{M-x edt-emulation-on}. @kbd{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. @item vi (Berkeley editor) @findex viper-mode Viper is the newest emulator for vi. It implements several levels of emulation; level 1 is closest to vi itself, while level 5 departs somewhat from strict emulation to take advantage of the capabilities of Emacs. To invoke Viper, type @kbd{M-x viper-mode}; it will guide you the rest of the way and ask for the emulation level. @inforef{Top, Viper, viper}. @item vi (another emulator) @findex vi-mode @kbd{M-x vi-mode} enters a major mode that replaces the previously established major mode. All of the vi commands that, in real vi, enter ``input'' mode are programmed instead 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 @code{vi-mode} command. @item vi (alternate emulator) @findex vip-mode @kbd{M-x vip-mode} invokes another vi emulator, said to resemble real vi more thoroughly than @kbd{M-x vi-mode}. ``Input'' mode in this emulator is changed from ordinary Emacs so you can use @key{ESC} to go back to emulated vi command mode. To get from emulated vi command mode back to ordinary Emacs, type @kbd{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 @code{vip-mode} as it is with @code{vi-mode} because terminating insert mode does not use it. @inforef{Top, VIP, vip}, for full information. @end table @node Dissociated Press, Amusements, Emulation, Top @section Dissociated Press @findex dissociated-press @kbd{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 @samp{*Dissociation*}, and redisplays that buffer after every couple of lines (approximately) so you can read the output as it comes out. Dissociated Press asks every so often whether to continue generating output. Answer @kbd{n} to stop it. You can also stop at any time by typing @kbd{C-g}. The dissociation output remains in the @samp{*Dissociation*} buffer for you to copy elsewhere if you wish. @cindex presidentagon 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'.@footnote{This dissociword actually appeared during the Vietnam War, when it was very appropriate.} Long sample texts produce the best results. @cindex againformation A positive argument to @kbd{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 @samp{*Dissociation*}. The buffer you start with is not changed. @cindex Markov chain @cindex ignoriginal @cindex techniquitous 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. @cindex outragedy @cindex buggestion @cindex properbose @cindex mustatement @cindex developediment @cindex userenced 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. @node Amusements, Customization, Dissociated Press, Top @section Other Amusements @cindex boredom @findex hanoi @findex yow @findex gomoku @findex mpuz @cindex tower of Hanoi If you are a little bit bored, you can try @kbd{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. @cindex Go Moku If you want a little more personal involvement, try @kbd{M-x gomoku}, which plays the game Go Moku with you. @findex blackbox @findex mpuz @cindex puzzles @kbd{M-x blackbox} and @kbd{M-x mpuz} are two kinds of puzzles. @code{blackbox} challenges you to determine the location of objects inside a box by tomography. @code{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. @findex dunnet @kbd{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 @kbd{M-x doctor}. End each input by typing @key{RET} twice. @cindex Zippy When you are feeling strange, type @kbd{M-x yow}.