@c This is part of the Emacs manual. @c Copyright (C) 1985--2024 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 Usenet news, host and network security, viewing PDFs and other such documents, web browsing, running shell commands and shell subprocesses, using a single shared Emacs for utilities that expect to run an editor as a subprocess, printing, sorting text, editing binary files, saving an Emacs session for later resumption, recursive editing level, following hyperlinks, and various diversions and amusements. @end iftex @ifnottex @raisesections @end ifnottex @node Gnus @section Email and Usenet News with Gnus @cindex Gnus @cindex Usenet news @cindex newsreader 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---email, remote directories, digests, and so on. Here we introduce Gnus and describe several basic features. @ifnottex For full details, see @ref{Top, Gnus,, gnus, The Gnus Manual}. @end ifnottex @iftex For full details on Gnus, type @kbd{C-h i} and then select the Gnus manual. @end iftex @menu * Buffers of Gnus:: The group, summary, and article buffers. * Gnus Startup:: What you should know about starting Gnus. * Gnus Group Buffer:: A short description of Gnus group commands. * Gnus Summary Buffer:: A short description of Gnus summary commands. @end menu @node Buffers of Gnus @subsection Gnus Buffers Gnus uses several buffers to display information and to receive commands. The three most commonly-used Gnus buffers are the @dfn{group buffer}, the @dfn{summary buffer} and the @dfn{article buffer}. The @dfn{group buffer} contains a list of article sources (e.g., newsgroups and email inboxes), which are collectively referred to as @dfn{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. From this buffer, you can select a group to read. The @dfn{summary buffer} lists the articles in a single group, showing one article per line. By default, it displays each article's author, subject, and line @iftex number. @end iftex @ifnottex number, but this is customizable; @xref{Summary Buffer Format,,, gnus, The Gnus Manual}. @end ifnottex The summary buffer is created when you select a group in the group buffer, and is killed when you exit the group. From the summary buffer, you can choose an article to view. The article is displayed in the @dfn{article buffer}. In normal Gnus usage, you view this buffer but do not select it---all useful Gnus commands can be invoked from the summary buffer. But you can select the article buffer, and execute Gnus commands from it, if you wish. @node Gnus Startup @subsection When Gnus Starts Up @findex gnus @cindex @file{.newsrc} file If your system has been set up for reading Usenet news, getting started with Gnus is easy---just type @kbd{M-x gnus}. On starting up, Gnus reads your @dfn{news initialization file}: a file named @file{.newsrc} in your home directory which lists your Usenet newsgroups and subscriptions (this file is not unique to Gnus; it is used by many other newsreader programs). It then tries to contact the system's default news server, which is typically specified by the @env{NNTPSERVER} environment variable. If your system does not have a default news server, or if you wish to use Gnus for reading email, then before invoking @kbd{M-x gnus} you need to tell Gnus where to get news and/or mail. To do this, customize the variables @code{gnus-select-method} and/or @code{gnus-secondary-select-methods}. @iftex See the Gnus manual for details. @end iftex @ifnottex @xref{Finding the News,,, gnus, The Gnus Manual}. @end ifnottex Once Gnus has started up, it displays the group buffer. By default, the group buffer shows only a small number of @dfn{subscribed groups}. Groups with other statuses---@dfn{unsubscribed}, @dfn{killed}, or @dfn{zombie}---are hidden. The first time you start Gnus, any group to which you are not subscribed is made into a killed group; any group that subsequently appears on the news server becomes a zombie group. To proceed, you must select a group in the group buffer to open the summary buffer for that group; then, select an article in the summary buffer to view its article buffer in a separate window. The following sections explain how to use the group and summary buffers to do this. To quit Gnus, type @kbd{q} in the group buffer. This automatically records your group statuses in the files @file{.newsrc} and @file{.newsrc.eld}, so that they take effect in subsequent Gnus sessions. @node Gnus Group Buffer @subsection Using the Gnus Group Buffer The following commands are available in the Gnus group buffer: @table @kbd @kindex SPC @r{(Gnus Group mode)} @findex gnus-group-read-group @item @key{SPC} Switch to the summary buffer for the group on the current line (@code{gnus-group-read-group}). @kindex l @r{(Gnus Group mode)} @kindex A s @r{(Gnus Group mode)} @findex gnus-group-list-groups @item l @itemx A s In the group buffer, list only the groups to which you subscribe and which contain unread articles (@code{gnus-group-list-groups}; this is the default listing). @kindex L @r{(Gnus Group mode)} @kindex A u @r{(Gnus Group mode)} @findex gnus-group-list-all-groups @item L @itemx A u List all subscribed and unsubscribed groups, but not killed or zombie groups (@code{gnus-group-list-all-groups}). @kindex A k @r{(Gnus Group mode)} @findex gnus-group-list-killed @item A k List killed groups (@code{gnus-group-list-killed}). @kindex A z @r{(Gnus Group mode)} @findex gnus-group-list-zombies @item A z List zombie groups (@code{gnus-group-list-zombies}). @kindex u @r{(Gnus Group mode)} @findex gnus-group-toggle-subscription-at-point @cindex subscribe groups @cindex unsubscribe groups @item u Toggle the subscription status of the group (@code{gnus-group-toggle-subscription-at-point}) on the current line. Invoking this on a killed or zombie group turns it into an unsubscribed group. @kindex C-k @r{(Gnus Group mode)} @findex gnus-group-kill-group @item C-k Kill the group on the current line (@code{gnus-group-kill-group}). Killed groups are not recorded in the @file{.newsrc} file, and they are not shown in the @kbd{l} or @kbd{L} listings. @kindex DEL @r{(Gnus Group mode)} @item @key{DEL} Move point to the previous group containing unread articles (@code{gnus-group-prev-unread-group}). @kindex n @r{(Gnus Group mode)} @findex gnus-group-next-unread-group @item n Move point to the next unread group (@code{gnus-group-next-unread-group}). @kindex p @r{(Gnus Group mode)} @findex gnus-group-prev-unread-group @item p Move point to the previous unread group (@code{gnus-group-prev-unread-group}). @kindex q @r{(Gnus Group mode)} @findex gnus-group-exit @item q Update your Gnus settings, and quit Gnus (@code{gnus-group-exit}). @end table @node Gnus Summary Buffer @subsection Using the Gnus Summary Buffer The following commands are available in the Gnus summary buffer: @table @kbd @kindex SPC @r{(Gnus Summary mode)} @findex gnus-summary-next-page @item @key{SPC} If there is no article selected, select the article on the current line and display its article buffer. Otherwise, try scrolling the selected article buffer in its window; on reaching the end of the buffer, select the next unread article (@code{gnus-summary-next-page}). Thus, you can read through all articles by repeatedly typing @key{SPC}. @kindex DEL @r{(Gnus Summary mode)} @findex gnus-summary-prev-page @item @key{DEL} Scroll the text of the article backwards (@code{gnus-summary-prev-page}). @kindex n @r{(Gnus Summary mode)} @findex gnus-summary-next-unread-article @item n Select the next unread article (@code{gnus-summary-next-unread-article}). @kindex p @r{(Gnus Summary mode)} @findex gnus-summary-prev-unread-article @item p Select the previous unread article (@code{gnus-summary-prev-unread-article}). @kindex s @r{(Gnus Summary mode)} @findex gnus-summary-isearch-article @item s Do an incremental search on the selected article buffer (@code{gnus-summary-isearch-article}), as if you switched to the buffer and typed @kbd{C-s} (@pxref{Incremental Search}). @kindex M-s M-s @r{(Gnus Summary mode)} @findex gnus-summary-search-article-forward @item M-s M-s @var{regexp} @key{RET} Search forward for articles containing a match for @var{regexp} (@code{gnus-summary-search-article-forward}). @kindex M-s M-r @r{(Gnus Summary mode)} @findex gnus-summary-search-article-backward @item M-r @var{regexp} @key{RET} Search back for articles containing a match for @var{regexp} (@code{gnus-summary-search-article-backward}). @kindex q @r{(Gnus Summary mode)} @item q Exit the summary buffer and return to the group buffer (@code{gnus-summary-exit}). @end table @node Host Security @section Host Security @cindex security Emacs runs inside an operating system such as GNU/Linux, and relies on the operating system to check security constraints such as accesses to files. The default settings for Emacs are designed for typical use; they may require some tailoring in environments where security is more of a concern, or less of a concern, than usual. For example, file-local variables can be risky, and you can set the variable @code{enable-local-variables} to @code{:safe} or (even more conservatively) to @code{nil}; conversely, if your files can all be trusted and the default checking for these variables is irritating, you can set @code{enable-local-variables} to @code{:all}. @xref{Safe File Variables}. @cindex trusted files and directories Loading a file of Emacs Lisp code with @code{load-file} or @code{load-library} (@pxref{Lisp Libraries}) can execute some of the Lisp code in the file being loaded, so you should only load Lisp files whose source you trust. However, some Emacs features can in certain situations execute Lisp code even without your explicit command or request. For example, Flymake, the on-the-fly syntax checker for Emacs (@pxref{Top,,, flymake, GNU Flymake}), if it is enabled, can automatically execute some of the code in a Lisp file you visit as part of its syntax-checking job. Similarly, some completion commands (@pxref{Completion}) in buffers visiting Lisp files sometimes need to expand Lisp macros for best results. In these cases, just visiting a Lisp file and performing some editing in it could trigger execution of Lisp code. If the visited file came from an untrusted source, it could include dangerous or even malicious code that Emacs would execute in those situations. To protect against this, Emacs disables execution of Lisp code by Flymake, completion, and some other features, unless the visited file is @dfn{trusted}. It is up to you to specify which files on your system should be trusted, by customizing the user option @code{trusted-content}. @defopt trusted-content The value of this option is @code{nil} by default, which means no file is trusted. You can customize the variable to be a list of one or more names of trusted files and directories. A file name that ends in a slash @file{/} is interpreted as a directory, which means all its files and subdirectories are also trusted. A special value @code{:all} means @emph{all} the files and directories on your system should be trusted; @strong{this is not recommended}, as it opens a gaping security hole. @end defopt @xref{Security Considerations,,, elisp, The Emacs Lisp Reference Manual}, for more information about security considerations when using Emacs as part of a larger application. @node Network Security @section Network Security @cindex network security manager @cindex NSM @cindex encryption @cindex SSL @cindex TLS @cindex Transport Layer Security @cindex STARTTLS Whenever Emacs establishes any network connection, it passes the established connection to the @dfn{Network Security Manager} (@acronym{NSM}). @acronym{NSM} is responsible for enforcing the network security under your control. Currently, this works by using the Transport Layer Security (@acronym{TLS}) features. @vindex network-security-level The @code{network-security-level} variable determines the security level that @acronym{NSM} enforces. If its value is @code{low}, no security checks are performed. This is not recommended, and will basically mean that your network connections can't be trusted. However, the setting can be useful in limited circumstances, as when testing network issues. If this variable is @code{medium} (which is the default), a number of checks will be performed. If as result @acronym{NSM} determines that the network connection might not be trustworthy, it will make you aware of that, and will ask you what to do about the network connection. You can decide to register a permanent security exception for an unverified connection, a temporary exception, or refuse the connection entirely. @vindex network-security-protocol-checks In addition to the basic certificate correctness checks, several @acronym{TLS} algorithm checks are available. Some encryption technologies that were previously thought to be secure have shown themselves to be fragile, so Emacs (by default) warns you about some of these problems. The protocol network checks is controlled via the @code{network-security-protocol-checks} variable. It's an alist where the first element of each association is the name of the check, and the second element is the security level where the check should be used. An element like @code{(rc4 medium)} will result in the function @code{nsm-protocol-check--rc4} being called like thus: @w{@code{(nsm-protocol-check--rc4 host port status settings)}}. The function should return non-@code{nil} if the connection should proceed and @code{nil} otherwise. Below is a list of the checks done on the default @code{medium} level. @table @asis @item unable to verify a @acronym{TLS} certificate If the connection is a @acronym{TLS}, @acronym{SSL} or @acronym{STARTTLS} connection, @acronym{NSM} will check whether the certificate used to establish the identity of the server we're connecting to can be verified. While an invalid certificate is often the cause for concern (there could be a Man-in-the-Middle hijacking your network connection and stealing your password), there may be valid reasons for going ahead with the connection anyway. For instance, the server may be using a self-signed certificate, or the certificate may have expired. It's up to you to determine whether it's acceptable to continue with the connection. @item a self-signed certificate has changed If you've previously accepted a self-signed certificate, but it has now changed, that could mean that the server has just changed the certificate, but it might also mean that the network connection has been hijacked. @item previously encrypted connection now unencrypted If the connection is unencrypted, but it was encrypted in previous sessions, this might mean that there is a proxy between you and the server that strips away @acronym{STARTTLS} announcements, leaving the connection unencrypted. This is usually very suspicious. @item talking to an unencrypted service when sending a password When connecting to an @acronym{IMAP} or @acronym{POP3} server, these should usually be encrypted, because it's common to send passwords over these connections. Similarly, if you're sending email via @acronym{SMTP} that requires a password, you usually want that connection to be encrypted. If the connection isn't encrypted, @acronym{NSM} will warn you. @item Diffie-Hellman low prime bits When doing the public key exchange, the number of prime bits should be high enough to ensure that the channel can't be eavesdropped on by third parties. If this number is too low, Emacs will warn you. (This is the @code{diffie-hellman-prime-bits} check in @code{network-security-protocol-checks}). @item @acronym{RC4} stream cipher The @acronym{RC4} stream cipher is believed to be of low quality and may allow eavesdropping by third parties. (This is the @code{rc4} check in @code{network-security-protocol-checks}). @item @acronym{SHA1} in the host certificate or in intermediate certificates It is believed that if an intermediate certificate uses the @acronym{SHA1} hashing algorithm, then third parties can issue certificates pretending to be that issuing instance. These connections are therefore vulnerable to man-in-the-middle attacks. (These are the @code{signature-sha1} and @code{intermediate-sha1} checks in @code{network-security-protocol-checks}). @item @acronym{SSL1}, @acronym{SSL2} and @acronym{SSL3} The protocols older than @acronym{TLS1.0} are believed to be vulnerable to a variety of attacks, and you may want to avoid using these if what you're doing requires higher security. (This is the @code{ssl} check in @code{network-security-protocol-checks}). @item Triple DES (or @acronym{3DES}) cipher The @acronym{3DES} stream cipher provides at most 112 bits of effective security, and a major security vulnerability in it was disclosed in 2016 (CVE-2016-2183). It has been deprecated by NIST in all applications from late 2023 onwards. (This is the @code{3des-cipher} check in @code{network-security-protocol-checks}). @end table If @code{network-security-level} is @code{high}, the following checks will be made, in addition to the above: @table @asis @item a validated certificate changes the public key Servers change their keys occasionally, and that is normally nothing to be concerned about. However, if you are worried that your network connections are being hijacked by agencies who have access to pliable Certificate Authorities which issue new certificates for third-party services, you may want to keep track of these changes. @end table Finally, if @code{network-security-level} is @code{paranoid}, you will also be notified the first time @acronym{NSM} sees any new certificate. This will allow you to inspect all the certificates from all the connections that Emacs makes. The following additional variables can be used to control details of @acronym{NSM} operation: @table @code @item nsm-settings-file @vindex nsm-settings-file This is the file where @acronym{NSM} stores details about connections. It defaults to @file{~/.emacs.d/network-security.data}. @item nsm-save-host-names @vindex nsm-save-host-names By default, host names will not be saved for non-@code{STARTTLS} connections. Instead a host/port hash is used to identify connections. This means that one can't casually read the settings file to see what servers the user has connected to. If this variable is @code{t}, @acronym{NSM} will also save host names in the @code{nsm-settings-file}. @end table @node Document View @section Document Viewing @cindex DVI file @cindex PDF file @cindex PS file @cindex PostScript file @cindex OpenDocument file @cindex Microsoft Office file @cindex EPUB file @cindex CBZ file @cindex FB2 file @cindex XPS file @cindex OXPS file @cindex DocView mode @cindex mode, DocView @cindex document viewer (DocView) @findex doc-view-mode DocView mode is a major mode for viewing DVI, PostScript (PS), PDF, OpenDocument, Microsoft Office, EPUB, CBZ, FB2, XPS and OXPS documents. It provides features such as slicing, zooming, and searching inside documents. It works by converting the document to a set of images using the @command{gs} (GhostScript) or @command{pdfdraw}/@command{mutool draw} (MuPDF) commands and other external tools, and then displays those converted images. @findex doc-view-toggle-display @findex doc-view-minor-mode When you visit a document file that can be displayed with DocView mode, Emacs automatically uses that mode @footnote{The needed external tools for the document type must be available, and Emacs must be running in a graphical frame and have PNG image support. If these requirements is not fulfilled, Emacs falls back to another major mode.}. As an exception, when you visit a PostScript file, Emacs switches to PS mode, a major mode for editing PostScript files as text; however, it also enables DocView minor mode, so you can type @kbd{C-c C-c} to view the document with DocView. In either DocView mode or DocView minor mode, repeating @kbd{C-c C-c} (@code{doc-view-toggle-display}) toggles between DocView and the underlying file contents. @findex doc-view-open-text When you visit a file which would normally be handled by DocView mode but some requirement is not met (e.g., you operate in a terminal frame or Emacs has no PNG support), you are queried if you want to view the document's contents as plain text. If you confirm, the buffer is put in text mode and DocView minor mode is activated. Thus, by typing @kbd{C-c C-c} you switch to the fallback mode. With another @kbd{C-c C-c} you return to DocView mode. The plain text contents can also be displayed from within DocView mode by typing @kbd{C-c C-t} (@code{doc-view-open-text}). You can explicitly enable DocView mode with the command @kbd{M-x doc-view-mode}. You can toggle DocView minor mode with @kbd{M-x doc-view-minor-mode}. When DocView mode starts, it displays a welcome screen and begins formatting the file, page by page. It displays the first page once that has been formatted. To kill the DocView buffer, type @kbd{k} (@code{doc-view-kill-proc-and-buffer}). To bury it, type @kbd{q} (@code{quit-window}). @menu * Navigation: DocView Navigation. Navigating DocView buffers. * Searching: DocView Searching. Searching inside documents. * Slicing: DocView Slicing. Specifying which part of a page is displayed. * Conversion: DocView Conversion. Influencing and triggering conversion. @end menu @node DocView Navigation @subsection DocView Navigation In DocView mode, you can scroll the current page using the usual Emacs movement keys: @kbd{C-p}, @kbd{C-n}, @kbd{C-b}, @kbd{C-f}, and the arrow keys. @vindex doc-view-continuous By default, the line-motion keys @kbd{C-p} and @kbd{C-n} stop scrolling at the beginning and end of the current page, respectively. However, if you change the variable @code{doc-view-continuous} to a non-@code{nil} value, then @kbd{C-p} displays the previous page if you are already at the beginning of the current page, and @kbd{C-n} displays the next page if you are at the end of the current page. @findex doc-view-next-page @findex doc-view-previous-page @kindex n @r{(DocView mode)} @kindex p @r{(DocView mode)} @kindex PageDown @r{(DocView mode)} @kindex PageUp @r{(DocView mode)} @kindex next @r{(DocView mode)} @kindex prior @r{(DocView mode)} @kindex C-x ] @r{(DocView mode)} @kindex C-x [ @r{(DocView mode)} You can also display the next page by typing @kbd{n}, @key{PageDown}, @key{next} or @kbd{C-x ]} (@code{doc-view-next-page}). To display the previous page, type @kbd{p}, @key{PageUp}, @key{prior} or @kbd{C-x [} (@code{doc-view-previous-page}). @findex doc-view-scroll-up-or-next-page @findex doc-view-scroll-down-or-previous-page @kindex SPC @r{(DocView mode)} @kindex DEL @r{(DocView mode)} @key{SPC} (@code{doc-view-scroll-up-or-next-page}) is a convenient way to advance through the document. It scrolls within the current page or advances to the next. @key{DEL} moves backwards in a similar way (@code{doc-view-scroll-down-or-previous-page}). @findex doc-view-first-page @findex doc-view-last-page @findex doc-view-goto-page @kindex M-< @r{(DocView mode)} @kindex M-> @r{(DocView mode)} To go to the first page, type @kbd{M-<} (@code{doc-view-first-page}); to go to the last one, type @kbd{M->} (@code{doc-view-last-page}). To jump to a page by its number, type @kbd{M-g M-g} or @kbd{M-g g} (@code{doc-view-goto-page}). @findex doc-view-enlarge @findex doc-view-shrink @vindex doc-view-resolution @vindex doc-view-scale-internally @kindex + @r{(DocView mode)} @kindex - @r{(DocView mode)} You can enlarge or shrink the document with @kbd{+} (@code{doc-view-enlarge}) and @kbd{-} (@code{doc-view-shrink}). By default, these commands just rescale the already-rendered image. If you instead want the image to be re-rendered at the new size, set @code{doc-view-scale-internally} to @code{nil}. To specify the default size for DocView, customize the variable @code{doc-view-resolution}. @vindex doc-view-imenu-enabled @vindex doc-view-imenu-flatten @vindex doc-view-imenu-format When the @command{mutool} program is available, DocView will use it to generate entries for an outline menu, making it accessible via the @code{imenu} facility (@pxref{Imenu}). To disable this functionality even when @command{mutool} can be found on your system, customize the variable @code{doc-view-imenu-enabled} to the @code{nil} value. You can further customize how @code{imenu} items are formatted and displayed using the variables @code{doc-view-imenu-format} and @code{doc-view-imenu-flatten}. @node DocView Searching @subsection DocView Searching In DocView mode, you can search the file's text for a regular expression (@pxref{Regexps}). The interface for searching is inspired by @code{isearch} (@pxref{Incremental Search}). @findex doc-view-search @findex doc-view-search-backward @findex doc-view-show-tooltip To begin a search, type @kbd{C-s} (@code{doc-view-search}) or @kbd{C-r} (@code{doc-view-search-backward}). This reads a regular expression using a minibuffer, then echoes the number of matches found within the document. You can move forward and back among the matches by typing @kbd{C-s} and @kbd{C-r}. DocView mode has no way to show the match inside the page image; instead, it displays a tooltip (at the mouse position) listing all matching lines in the current page. To force display of this tooltip, type @kbd{C-t} (@code{doc-view-show-tooltip}). To start a new search, use the search command with a prefix argument; i.e., @kbd{C-u C-s} for a forward search or @kbd{C-u C-r} for a backward search. @node DocView Slicing @subsection DocView Slicing Documents often have wide margins for printing. They are annoying when reading the document on the screen, because they use up screen space and can cause inconvenient scrolling. @findex doc-view-set-slice @findex doc-view-set-slice-using-mouse With DocView you can hide these margins by selecting a @dfn{slice} of pages to display. A slice is a rectangle within the page area; once you specify a slice in DocView, it applies to whichever page you look at. To specify the slice numerically, type @kbd{c s} (@code{doc-view-set-slice}); then enter the top left pixel position and the slice's width and height. @c ??? how does this work? A more convenient graphical way to specify the slice is with @kbd{c m} (@code{doc-view-set-slice-using-mouse}), where you use the mouse to select the slice. Simply press and hold the left mouse button at the upper-left corner of the region you want to have in the slice, then move the mouse pointer to the lower-right corner and release the button. The most convenient way is to set the optimal slice by using BoundingBox information automatically determined from the document by typing @kbd{c b} (@code{doc-view-set-slice-from-bounding-box}). @findex doc-view-reset-slice To cancel the selected slice, type @kbd{c r} (@code{doc-view-reset-slice}). Then DocView shows the entire page including its entire margins. @node DocView Conversion @subsection DocView Conversion @vindex doc-view-cache-directory @findex doc-view-clear-cache For efficiency, DocView caches the images produced by @command{gs}. The name of the directory where it caches images is given by the variable @code{doc-view-cache-directory}. You can clear the cache directory by typing @kbd{M-x doc-view-clear-cache}. @findex doc-view-kill-proc @findex doc-view-kill-proc-and-buffer To force reconversion of the currently viewed document, type @kbd{r} or @kbd{g} (@code{revert-buffer}). To kill the converter process associated with the current buffer, type @kbd{K} (@code{doc-view-kill-proc}). The command @kbd{k} (@code{doc-view-kill-proc-and-buffer}) kills the converter process and the DocView buffer. @node Shell @section Running Shell Commands from Emacs @cindex subshell @cindex shell commands Emacs has commands for passing single command lines to shell subprocesses, and for running a shell interactively with input and output to an Emacs buffer, and for running a shell in a terminal emulator window. @table @kbd @item M-! @var{cmd} @key{RET} Run the shell command @var{cmd} and display the output (@code{shell-command}). @item M-| @var{cmd} @key{RET} Run the shell command @var{cmd} with region contents as input; optionally replace the region with the output (@code{shell-command-on-region}). @item M-& @var{cmd} @key{RET} Run the shell command @var{cmd} asynchronously, and display the output (@code{async-shell-command}). @item M-x shell Run a subshell with input and output through an Emacs buffer. You can then give commands interactively. @item M-x term Run a subshell with input and output through an Emacs buffer. You can then give commands interactively. Full terminal emulation is available. @end table @vindex exec-path Whenever you specify a relative file name for an executable program (either in the @var{cmd} argument to one of the above commands, or in other contexts), Emacs searches for the program in the directories specified by the variable @code{exec-path}. The value of this variable must be a list of directories; the default value is initialized from the environment variable @env{PATH} when Emacs is started (@pxref{General Variables}). @kbd{M-x eshell} invokes a shell implemented entirely in Emacs. It is documented in its own manual. @ifnottex @xref{Top,Eshell,Eshell, eshell, Eshell: The Emacs Shell}. @end ifnottex @iftex See the Eshell Info manual, which is distributed with Emacs. @end iftex @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. * Shell Prompts:: Two ways to recognize shell prompts. * History: Shell History. Repeating previous commands in a shell buffer. * Directory Tracking:: Keeping track when the subshell changes directory. * Options: Shell Options. Options for customizing Shell mode. * Terminal emulator:: An Emacs window as a terminal emulator. * Term Mode:: Special Emacs commands used in Term mode. * Remote Host:: Connecting to another computer. * Serial Terminal:: Connecting to a serial port. @end menu @node Single Shell @subsection Single Shell Commands @kindex M-! @findex shell-command @vindex shell-command-buffer-name @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 appears either in the echo area (if it is short), or in the @samp{"*Shell Command Output*"} (@code{shell-command-buffer-name}) buffer (if the output is long). The variables @code{resize-mini-windows} and @code{max-mini-window-height} (@pxref{Minibuffer Edit}) control when Emacs should consider the output to be too long for the echo area. Note that customizing @code{shell-command-dont-erase-buffer}, described below, can affect what is displayed in the echo area. For instance, one way to decompress a file named @file{foo.gz} is to type @kbd{M-! gunzip foo.gz @key{RET}}. That shell command normally creates the file @file{foo} and produces no terminal output. A numeric argument to @code{shell-command}, e.g., @kbd{M-1 M-!}, causes it to insert terminal output into the current buffer instead of a separate buffer. By default, it puts point before the output, and sets the mark after the output (but a non-default value of @code{shell-command-dont-erase-buffer} can change that, see below). For instance, @kbd{M-1 M-! gunzip < foo.gz @key{RET}} would insert the uncompressed form of the file @file{foo.gz} into the current buffer. Provided the specified shell command does not end with @samp{&}, it runs @dfn{synchronously}, and you must wait for it to exit before continuing to use Emacs. To stop waiting, type @kbd{C-g} to quit; this sends a @code{SIGINT} signal to terminate the shell command (this is the same signal that @kbd{C-c} normally generates in the shell). Emacs then 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. @kindex M-& @findex async-shell-command @vindex shell-command-buffer-name-async A shell command that ends in @samp{&} is executed @dfn{asynchronously}, and you can continue to use Emacs as it runs. You can also type @kbd{M-&} (@code{async-shell-command}) to execute a shell command asynchronously; this is exactly like calling @kbd{M-!} with a trailing @samp{&}, except that you do not need the @samp{&}. The output from asynchronous shell commands, by default, goes into the @samp{"*Async Shell Command*"} buffer (@code{shell-command-buffer-name-async}). Emacs inserts the output into this buffer as it comes in, whether or not the buffer is visible in a window. @vindex async-shell-command-buffer If you want to run more than one asynchronous shell command at the same time, they could end up competing for the output buffer. The option @code{async-shell-command-buffer} specifies what to do about this; e.g., whether to rename the pre-existing output buffer, or to use a different buffer for the new command. Consult the variable's documentation for more possibilities. @vindex async-shell-command-display-buffer If you want the output buffer for asynchronous shell commands to be displayed only when the command generates output, set @code{async-shell-command-display-buffer} to @code{nil}. @vindex async-shell-command-width The option @code{async-shell-command-width} defines the number of display columns available for output of asynchronous shell commands. A positive integer tells the shell to use that number of columns for command output. The default value is @code{nil} that means to use the same number of columns as provided by the shell. @vindex shell-command-prompt-show-cwd To make the above commands show the current directory in their prompts, customize the variable @code{shell-command-prompt-show-cwd} to a non-@code{nil} value. @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. With a numeric argument, it deletes the old region and replaces it with the output from the shell command. For example, you can use @kbd{M-|} with the @command{gpg} program to see what keys are in the buffer. If the buffer contains a GnuPG key, type @kbd{C-x h M-| gpg @key{RET}} to feed the entire buffer contents to @command{gpg}. This will output the list of keys to the buffer whose name is the value of @code{shell-command-buffer-name}. @vindex shell-file-name @cindex @env{SHELL} environment variable The above commands use the shell specified by the variable @code{shell-file-name}. Its default value is determined by the @env{SHELL} environment variable when Emacs is started. If the file name is relative, Emacs searches the directories listed in @code{exec-path} (@pxref{Shell}). If the default directory is remote (@pxref{Remote Files}), the default value is @file{/bin/sh}. This can be changed by declaring @code{shell-file-name} connection-local (@pxref{Connection Variables}). To specify a coding system for @kbd{M-!} or @kbd{M-|}, use the command @kbd{C-x @key{RET} c} immediately beforehand. @xref{Communication Coding}. @vindex shell-command-default-error-buffer By default, error output is intermixed with the regular output in the output buffer. But if you change the value of the variable @code{shell-command-default-error-buffer} to a string, error output is inserted into a buffer of that name. @vindex shell-command-dont-erase-buffer By default, the output buffer is erased between shell commands, except when the output goes to the current buffer. If you change the value of the option @code{shell-command-dont-erase-buffer} to @code{erase}, then the output buffer is always erased. Other non-@code{nil} values prevent erasing of the output buffer, and---if the output buffer is not the current buffer---also control where to put point after inserting the output of the shell command: @table @code @item beg-last-out Puts point at the beginning of the last shell-command output. @item end-last-out Puts point at the end of the last shell-command output, i.e.@: at the end of the output buffer. @item save-point Restores the position of point as it was before inserting the shell-command output. @end table Note that if this option is non-@code{nil}, the output shown in the echo area could be from more than just the last command, since the echo area just displays a portion of the output buffer. In case the output buffer is not the current buffer, shell command output is appended at the end of this buffer. @node Interactive Shell @subsection Interactive Subshell @findex shell To run a subshell interactively, type @kbd{M-x shell}. This creates (or reuses) a buffer named @file{*shell*}, and runs a shell subprocess 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}. By default, when the subshell is invoked interactively, the @file{*shell*} buffer is displayed in a new window, unless the current window already shows the @file{*shell*} buffer. This behavior can be customized via @code{display-buffer-alist} (@pxref{Window Choice}). While the subshell is waiting or running a command, you can switch windows or buffers and perform other editing in Emacs. Emacs inserts the output from the subshell into the Shell buffer whenever it has time to process it (e.g., while waiting for keyboard input). @cindex @code{comint-highlight-input} face @cindex @code{comint-highlight-prompt} face In the Shell buffer, prompts are displayed with the face @code{comint-highlight-prompt}, and submitted input lines are displayed with the face @code{comint-highlight-input}. This makes it easier to distinguish input lines from the shell output. @xref{Faces}. To make multiple subshells, invoke @kbd{M-x shell} with a prefix argument (e.g., @kbd{C-u M-x shell}). Then the command will read a buffer name, and create (or reuse) a subshell in that buffer. You can also rename the @file{*shell*} buffer using @kbd{M-x rename-uniquely}, then create a new @file{*shell*} buffer using plain @kbd{M-x shell}. Subshells in different buffers run independently and in parallel. Emacs attempts to keep track of what the current directory is by looking at the commands you enter, looking for @samp{cd} commands and the like. This is an error-prone solution, since there are many ways to change the current directory, so Emacs also looks for special @acronym{OSC} (Operating System Commands) escape codes that are designed to convey this information in a more reliable fashion. You should arrange for your shell to print the appropriate escape sequence at each prompt, for instance with the following command: @example printf "\e]7;file://%s%s\e\\" "$HOSTNAME" "$PWD" @end example @vindex explicit-shell-file-name @cindex environment variables for subshells @cindex @env{ESHELL} environment variable To specify the shell file name used by @kbd{M-x shell}, customize the variable @code{explicit-shell-file-name}. If this is @code{nil} (the default), Emacs uses the environment variable @env{ESHELL} if it exists. Otherwise, it usually uses the variable @code{shell-file-name} (@pxref{Single Shell}); but if the default directory is remote (@pxref{Remote Files}), it prompts you for the shell file name. @xref{Minibuffer File}, for hints how to type remote file names effectively. Emacs sends the new shell the contents of the file @file{~/.emacs_@var{shellname}} as input, if it 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}. If this file is not found, Emacs tries with @file{~/.emacs.d/init_@var{shellname}.sh}. 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 change the coding system for a running subshell by typing @kbd{C-x @key{RET} p} in the shell buffer. @xref{Communication Coding}. @cindex @env{INSIDE_EMACS} environment variable Emacs sets the environment variable @env{INSIDE_EMACS} in the subshell to @samp{@var{version},comint}, where @var{version} is the Emacs version (e.g., @samp{28.1}). Programs can check this variable to determine whether they are running inside an Emacs subshell. @node Shell Mode @subsection Shell Mode @cindex Shell mode @cindex mode, Shell The major mode for Shell buffers is Shell mode. Many of its special commands are bound to the @kbd{C-c} prefix, and resemble the usual editing and job control characters present in ordinary shells, except that you must type @kbd{C-c} first. Here is a list of Shell mode commands: @table @kbd @item @key{RET} @kindex RET @r{(Shell mode)} @findex comint-send-input Send the current line as input to the subshell (@code{comint-send-input}). Any shell prompt at the beginning of the line is omitted (@pxref{Shell Prompts}). If point is at the end of buffer, this is like submitting the command line in an ordinary interactive shell. However, you can also invoke @key{RET} elsewhere in the shell buffer to submit the current line as input. @item @key{TAB} @kindex TAB @r{(Shell mode)} @findex completion-at-point@r{, in Shell Mode} @cindex shell completion Complete the command name or file name before point in the shell buffer (@code{completion-at-point}). This uses the usual Emacs completion rules (@pxref{Completion}), with the completion alternatives being file names, environment variable names, the shell command history, and history references (@pxref{History References}). For options controlling the completion, @pxref{Shell Options}. @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 (@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 @acronym{EOF} (@code{comint-delchar-or-maybe-eof}). Typed at the end of the shell buffer, this sends @acronym{EOF} to the subshell. Typed at any other position in the buffer, this deletes a character as usual. @item C-c C-a @kindex C-c C-a @r{(Shell mode)} @findex comint-bol-or-process-mark Move to the beginning of the line, but after the prompt if any (@code{comint-bol-or-process-mark}). 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 (@code{comint-accumulate}). 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}). If point is not at end of buffer, this only kills the part of this text that precedes point. @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-delete-output Delete the last batch of output from a shell command (@code{comint-delete-output}). This is useful if a shell command spews out lots of output that just gets in the way. With a prefix argument, this command saves the deleted text in the @code{kill-ring} (@pxref{Kill Ring}), so that you could later yank it (@pxref{Yanking}) elsewhere. @item C-c C-s @kindex C-c C-s @r{(Shell mode)} @findex comint-write-output Write the last batch of output from a shell command to a file (@code{comint-write-output}). With a prefix argument, the file is appended to instead. Any prompt at the end of the output is not written. @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 last line 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 M-x dirs Ask the shell for its working directory, and update the Shell buffer's default directory. @xref{Directory Tracking}. @item M-x comint-send-invisible @key{RET} @var{text} @key{RET} @findex comint-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. Please note that Emacs will not echo passwords by default. If you really want them to be echoed, evaluate (@pxref{Lisp Eval}) the following Lisp expression: @example (remove-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 By default, Shell mode handles common @acronym{ANSI} escape codes (for instance, for changing the color of text). Emacs also optionally supports some extend escape codes, like some of the @acronym{OSC} (Operating System Codes) if you put the following in your init file: @lisp (add-hook 'comint-output-filter-functions 'comint-osc-process-output) @end lisp With this enabled, the output from, for instance, @code{ls --hyperlink} will be made into clickable buttons in the Shell mode 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 include 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. To pass arguments to the program, use @kbd{C-u M-x comint-run}. @node Shell Prompts @subsection Shell Prompts @cindex prompt, shell A prompt is text output by a program to show that it is ready to accept new user input. Normally, Comint mode (and thus Shell mode) automatically figures out which part of the buffer is a prompt, based on the output of the subprocess. (Specifically, it assumes that any received output line which doesn't end with a newline is a prompt.) Comint mode divides the buffer into two types of @dfn{fields}: input fields (where user input is typed) and output fields (everywhere else). Prompts are part of the output fields. Most Emacs motion commands do not cross field boundaries, unless they move over multiple lines. For instance, when point is in the input field on a shell command line, @kbd{C-a} puts point at the beginning of the input field, after the prompt. Internally, the fields are implemented using the @code{field} text property (@pxref{Text Properties,,, elisp, the Emacs Lisp Reference Manual}). @vindex comint-use-prompt-regexp @vindex shell-prompt-pattern If you change the variable @code{comint-use-prompt-regexp} to a non-@code{nil} value, then Comint mode will recognize prompts using a regular expression (@pxref{Regexps}). In Shell mode, the regular expression is specified by the variable @code{shell-prompt-pattern}. The default value of @code{comint-use-prompt-regexp} is @code{nil}, because this method for recognizing prompts is unreliable, but you may want to set it to a non-@code{nil} value in unusual circumstances. In that case, Emacs does not divide the Comint buffer into fields, so the general motion commands behave as they normally do in buffers without special text properties. However, you can use the paragraph motion commands to conveniently navigate the buffer (@pxref{Paragraphs}); in Shell mode, Emacs uses @code{shell-prompt-pattern} as paragraph boundaries. @node Shell History @subsection Shell Command History Shell buffers support three ways of repeating earlier commands. You can use keys like those used for the minibuffer history; 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 @itemx C-@key{UP} Fetch the next earlier old shell command (@code{comint-previous-input}). @kindex M-n @r{(Shell mode)} @findex comint-next-input @item M-n @itemx C-@key{DOWN} Fetch the next later old shell command (@code{comint-next-input}). @kindex M-r @r{(Shell mode)} @findex comint-history-isearch-backward-regexp @item M-r Begin an incremental regexp search of old shell commands (@code{comint-history-isearch-backward-regexp}). @item C-c C-x @kindex C-c C-x @r{(Shell mode)} @findex comint-get-next-from-history Fetch the next subsequent command from the history (@code{comint-get-next-from-history}). @item C-c . @kindex C-c . @r{(Shell mode)} @findex comint-insert-previous-argument Fetch one argument from an old shell command (@code{comint-input-previous-argument}). @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}). @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}, and @kbd{M-r}. These work similar to the minibuffer history commands (@pxref{Minibuffer History}), except that they operate within the Shell buffer rather than the minibuffer, and @code{M-r} in a Shell buffer invokes incremental search through shell command history. @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. @kbd{C-@key{UP}} works like @kbd{M-p}, and @kbd{C-@key{DOWN}} like @kbd{M-n}. The history search command @kbd{M-r} begins an incremental regular expression search of previous shell commands. After typing @kbd{M-r}, start typing the desired string or regular expression; the last matching shell command will be displayed in the current line. Incremental search commands have their usual effects---for instance, @kbd{C-s} and @kbd{C-r} search forward and backward for the next match (@pxref{Incremental Search}). When you find the desired input, type @key{RET} to terminate the search. This puts the input in the command line. Any partial input you were composing before navigating the history list is restored when you go to the beginning or end of the history ring. 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. The command @kbd{C-c .}@: (@code{comint-insert-previous-argument}) copies an individual argument from a previous command, like @kbd{@key{ESC} .}@: in Bash and @command{zsh}. The simplest use copies the last argument from the previous shell command. With a prefix argument @var{n}, it copies the @var{n}th argument instead. Repeating @kbd{C-c .} copies from an earlier shell commands, always using the same value of @var{n} (don't give a prefix argument when you repeat the @kbd{C-c .} command). @vindex comint-insert-previous-argument-from-end If you set @code{comint-insert-previous-argument-from-end} to a non-@code{nil} value, @kbd{C-c .}@: will instead copy the @var{n}th argument counting from the last one; this emulates @kbd{@key{ESC} .}@: in @command{zsh}. 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 comint-input-ring-file-name @vindex shell-history-file-name @cindex @env{HISTFILE} environment variable Some shells store their command histories in files so that you can refer to commands from previous shell sessions. Emacs reads the command history file for your chosen shell, to initialize its own command history. The history file name is the string specified in @code{shell-history-file-name}. If that user option is @code{t}, the command history is not read. If the value is @code{nil}, the command history is read from the file specified in environment variable @env{HISTFILE}, or from @file{~/.bash_history} for bash, @file{~/.sh_history} for ksh, @file{~/.zsh_history"} for zsh, or @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 at point, 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. If you use this command on an output line, it copies that line to the end of the buffer. @item mouse-2 If @code{comint-use-prompt-regexp} is @code{nil} (the default), copy the old input command that you click on, inserting the copy at the end of the buffer (@code{comint-insert-input}). If @code{comint-use-prompt-regexp} is non-@code{nil}, or if the click is not over old input, just yank as usual. @end table Moving to a previous input and then copying it with @kbd{C-c @key{RET}} or @kbd{mouse-2} 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 recognizes these constructs, and can 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 comint-input-autoexpand @findex comint-magic-space 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}. You can make @key{SPC} perform history expansion by binding @key{SPC} to the command @code{comint-magic-space}. @xref{Rebinding}. Shell mode recognizes history references when they follow a prompt. @xref{Shell Prompts}, for how Shell mode recognizes prompts. @node Directory Tracking @subsection Directory Tracking @cindex directory tracking @vindex shell-pushd-regexp @vindex shell-popd-regexp @vindex shell-cd-regexp Shell mode keeps track of @samp{cd}, @samp{pushd} and @samp{popd} commands given to the subshell, in order to keep the Shell buffer's default directory (@pxref{File Names}) the same as the shell's working directory. It recognizes these commands by examining lines of input that you send. If you use aliases for these commands, you can tell Emacs to recognize them also, by setting the variables @code{shell-pushd-regexp}, @code{shell-popd-regexp}, and @code{shell-cd-regexp} to the appropriate regular expressions (@pxref{Regexps}). For example, if @code{shell-pushd-regexp} matches the beginning of a shell command line, that line is regarded as a @code{pushd} command. These commands are recognized only at the beginning of a shell command line. @findex dirs If Emacs gets confused about changes in the working directory of the subshell, type @kbd{M-x dirs}. This command asks the shell for its working directory and updates the default directory accordingly. It works for shells that support the most common command syntax, but may not work for unusual shells. @findex dirtrack-mode @cindex Dirtrack mode @cindex mode, Dirtrack @vindex dirtrack-list You can also use Dirtrack mode, a buffer-local minor mode that implements an alternative method of tracking the shell's working directory. To use this method, your shell prompt must contain the working directory at all times, and you must supply a regular expression for recognizing which part of the prompt contains the working directory; see the documentation of the variable @code{dirtrack-list} for details. To use Dirtrack mode, type @kbd{M-x dirtrack-mode} in the Shell buffer, or add @code{dirtrack-mode} to @code{shell-mode-hook} (@pxref{Hooks}). @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. The default is @code{nil}. @vindex comint-scroll-show-maximum-output If @code{comint-scroll-show-maximum-output} is non-@code{nil}, then arrival of output when point is at the end tries to scroll the last line of text to the bottom line of the window, showing as much useful text as possible. (This mimics the scrolling behavior of most terminals.) The default is @code{t}. @vindex comint-move-point-for-output By setting @code{comint-move-point-for-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-prompt-read-only If you set @code{comint-prompt-read-only}, the prompts in the Comint buffer are read-only. @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. @vindex shell-completion-execonly Command completion normally considers only executable files. If you set @code{shell-completion-execonly} to @code{nil}, it considers nonexecutable files as well. @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 is @code{nil}, but some users prefer @code{("~" "#" "%")} to ignore file names ending in @samp{~}, @samp{#} or @samp{%}. Other related Comint modes use the variable @code{comint-completion-fignore} instead. @findex shell-dynamic-complete-command Some implementation details of the shell command completion may also be found in the lisp documentation of the @code{shell-dynamic-complete-command} function. @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. @vindex comint-terminfo-terminal @vindex system-uses-terminfo @vindex TERM@r{, environment variable, in sub-shell} Comint mode sets the @env{TERM} environment variable to a safe default value, but this value disables some useful features. For example, color is disabled in applications that use @env{TERM} to determine if color is supported. Therefore, Emacs provides an option @code{comint-terminfo-terminal} to let you choose a terminal with more advanced features, as defined in your system's terminfo database. Emacs will use this option as the value for @env{TERM} so long as @code{system-uses-terminfo} is non-@code{nil}. Both @code{comint-terminfo-terminal} and @code{system-uses-terminfo} can be declared as connection-local variables to adjust these options to match what a remote system expects (@pxref{Connection Variables}). @node Terminal emulator @subsection Emacs Terminal Emulator @findex term To run a subshell in a text terminal emulator, use @kbd{M-x term}. This creates (or reuses) a buffer named @file{*terminal*}, and runs a subshell with input coming from your keyboard, and output going to that buffer. @cindex line mode @r{(terminal emulator)} @cindex char mode @r{(terminal emulator)} The terminal emulator uses Term mode, which has two input modes. In @dfn{line mode}, Term basically acts like Shell mode (@pxref{Shell Mode}). In @dfn{char mode}, each character is sent directly to the subshell, as terminal input; the sole exception is the terminal escape character, which by default is @kbd{C-c} (@pxref{Term Mode}). Any echoing of your input is the responsibility of the subshell; any terminal output from the subshell goes into the buffer, advancing point. Some programs (such as Emacs itself) need to control the appearance of the terminal screen in detail. They do this by emitting special control codes. Term mode recognizes and handles ANSI-standard VT100-style escape sequences, which are accepted by most modern terminals, including @command{xterm}. (Hence, you can actually run Emacs inside an Emacs Term window.) The @code{term} face specifies the default appearance of text in the terminal emulator (the default is the same appearance as the @code{default} face). When terminal control codes are used to change the appearance of text, these are represented in the terminal emulator by the faces @code{term-color-black}, @code{term-color-red}, @code{term-color-green}, @code{term-color-yellow} @code{term-color-blue}, @code{term-color-magenta}, @code{term-color-cyan}, @code{term-color-white}, @code{term-color-underline}, and @code{term-color-bold}. @xref{Faces}. You can also use Term mode to communicate with a device connected to a serial port. @xref{Serial Terminal}. The file name used to load the subshell is determined the same way as for Shell mode. To make multiple terminal emulators, rename the buffer @file{*terminal*} to something different using @kbd{M-x rename-uniquely}, just as with Shell mode. Unlike Shell mode, Term mode does not track the current directory by examining your input. But some shells can tell Term what the current directory is. This is done automatically by @code{bash} version 1.15 and later. @node Term Mode @subsection Term Mode @cindex Term mode @cindex mode, Term To switch between line and char mode in Term mode, use these commands: @table @kbd @kindex C-c C-j @r{(Term mode)} @findex term-line-mode @item C-c C-j Switch to line mode (@code{term-line-mode}). Do nothing if already in line mode. @kindex C-c C-k @r{(Term mode)} @findex term-char-mode @item C-c C-k Switch to char mode (@code{term-char-mode}). Do nothing if already in char mode. @end table The following commands are only available in char mode: @table @kbd @item C-c C-c Send a literal @kbd{C-c} to the sub-shell (@code{term-interrupt-subjob}). @item C-c @var{char} This is equivalent to @kbd{C-x @var{char}} in normal Emacs. For example, @kbd{C-c o} invokes the global binding of @kbd{C-x o}, which is normally @samp{other-window}. @end table @cindex paging in Term mode Term mode has a page-at-a-time feature. When enabled, it makes output pause at the end of each screenful: @table @kbd @kindex C-c C-q @r{(Term mode)} @findex term-pager-toggle @item C-c C-q Toggle the page-at-a-time feature (@code{term-pager-toggle}). This command works in both line and char modes. When the feature is enabled, the mode-line displays the word @samp{page}, and each time Term receives more than a screenful of output, it pauses and displays @samp{**MORE**} in the mode-line. Type @key{SPC} to display the next screenful of output, or @kbd{?} to see your other options. The interface is similar to the @code{more} program. @end table @node Remote Host @subsection Remote Host Shell @cindex remote host @cindex connecting to remote host @cindex Telnet @cindex SSH You can login to a remote computer, using whatever commands you would from a regular terminal (e.g., the @command{ssh} command), from a Term window. A program that asks you for a password will normally suppress echoing of the password, so the password will not show up in the buffer. This will happen just as if you were using a real terminal, if the buffer is in char mode. If it is in line mode, the password is temporarily visible, but will be erased when you hit return. (This happens automatically; there is no special password processing.) When you log in to a different machine, you need to specify the type of terminal you're using, by setting the @env{TERM} environment variable in the environment for the remote login command. (If you use bash, you do that by writing the variable assignment before the remote login command, without a separating comma.) Terminal types @samp{ansi} or @samp{vt100} will work on most systems. @node Serial Terminal @subsection Serial Terminal @cindex terminal, serial @findex serial-term If you have a device connected to a serial port of your computer, you can communicate with it by typing @kbd{M-x serial-term}. This command asks for a serial port name and speed, and switches to a new Term mode buffer. Emacs communicates with the serial device through this buffer just like it does with a terminal in ordinary Term mode. The speed of the serial port is measured in bits per second. The most common speed is 9600 bits per second. You can change the speed interactively by clicking on the mode line. A serial port can be configured even more by clicking on @samp{8N1} in the mode line. By default, a serial port is configured as @samp{8N1}, which means that each byte consists of 8 data bits, No parity check bit, and 1 stopbit. If the speed or the configuration is wrong, you cannot communicate with your device and will probably only see garbage output in the window. @node Emacs Server @section Using Emacs as a Server @pindex emacsclient @cindex Emacs as a server @cindex server, using Emacs as @cindex @env{EDITOR} environment variable Various programs can invoke your choice of editor to edit a particular piece of text. For instance, version control programs invoke an editor to enter version control logs (@pxref{Version Control}), and the Unix @command{mail} utility invokes an editor to enter a message to send. By convention, your choice of editor is specified by the environment variable @env{EDITOR}. If you set @env{EDITOR} to @samp{emacs}, Emacs would be invoked, but in an inconvenient way---by starting a new Emacs process. This is inconvenient because the new Emacs process doesn't share buffers, a command history, or other kinds of information with any existing Emacs process. You can solve this problem by setting up Emacs as an @dfn{edit server}, so that it ``listens'' for external edit requests and acts accordingly. There are various ways to start an Emacs server: @itemize @findex server-start @item Run the command @code{server-start} in an existing Emacs process: either type @kbd{M-x server-start}, or put the expression @code{(server-start)} in your init file (@pxref{Init File}). The existing Emacs process is the server; when you exit Emacs, the server dies with the Emacs process. @cindex daemon, Emacs @item Run Emacs as a @dfn{daemon}, using one of the @samp{--daemon} command-line options. @xref{Initial Options}. When Emacs is started this way, it calls @code{server-start} after initialization and does not open an initial frame. It then waits for edit requests from clients. @item Run the command @code{emacsclient} with the @samp{--alternate-editor=""} command-line option. This starts an Emacs daemon only if no Emacs daemon is already running. @cindex systemd unit file @item If your operating system uses @command{systemd} to manage startup, you can automatically start Emacs in daemon mode when you login using the supplied @dfn{systemd unit file}. To activate this: @example systemctl --user enable emacs @end example (If your Emacs was installed into a non-standard location, you may need to copy the @file{emacs.service} file to a standard directory such as @file{~/.config/systemd/user/}.) @cindex socket activation, systemd, Emacs @item An external process can invoke the Emacs server when a connection event occurs upon a specified socket and pass the socket to the new Emacs server process. An instance of this is the socket functionality of @command{systemd}: the @command{systemd} service creates a socket and listens for connections on it; when @command{emacsclient} connects to it for the first time, @command{systemd} can launch the Emacs server and hand over the socket to it for servicing @command{emacsclient} connections. A setup to use this functionality could be: @file{~/.config/systemd/user/emacs.socket}: @example [Socket] ListenStream=/path/to/.emacs.socket DirectoryMode=0700 [Install] WantedBy=sockets.target @end example (The @file{emacs.service} file described above must also be installed.) The @code{ListenStream} path will be the path that Emacs listens for connections from @command{emacsclient}; this is a file of your choice. @end itemize @cindex @env{TEXEDIT} environment variable Once an Emacs server is started, you can use a shell command called @command{emacsclient} to connect to the Emacs process and tell it to visit a file. You can then set the @env{EDITOR} environment variable to @samp{emacsclient}, so that external programs will use the existing Emacs process for editing.@footnote{Some programs use a different environment variable; for example, to make @TeX{} use @samp{emacsclient}, set the @env{TEXEDIT} environment variable to @samp{emacsclient +%d %s}.} @vindex server-name You can run multiple Emacs servers on the same machine by giving each one a unique @dfn{server name}, using the variable @code{server-name}. For example, @kbd{M-x set-variable @key{RET} server-name @key{RET} "foo" @key{RET}} sets the server name to @samp{foo}. The @code{emacsclient} program can specify a server by name, using the @samp{-s} or the @samp{-f} option (@pxref{emacsclient Options}), depending on whether or not the server uses a TCP socket (@pxref{TCP Emacs server}). If you want to run multiple Emacs daemons (@pxref{Initial Options}), you can give each daemon its own server name like this: @example emacs --daemon=foo @end example @vindex server-stop-automatically The Emacs server can optionally be stopped automatically when certain conditions are met. To do this, set the option @code{server-stop-automatically} to one of the following values: @table @code @item empty This value causes the server to be stopped when it has no clients, no unsaved file-visiting buffers and no running processes anymore. @item delete-frame This value means that when the last client frame is being closed, you are asked whether each unsaved file-visiting buffer must be saved and each unfinished process can be stopped, and if so, the server is stopped. @item kill-terminal This value means that when the last client frame is being closed with @kbd{C-x C-c} (@code{save-buffers-kill-terminal}), you are asked whether each unsaved file-visiting buffer must be saved and each unfinished process can be stopped, and if so, the server is stopped. @end table @findex server-eval-at If you have defined a server by a unique server name, it is possible to connect to the server from another Emacs instance and evaluate Lisp expressions on the server, using the @code{server-eval-at} function. For instance, @code{(server-eval-at "foo" '(+ 1 2))} evaluates the expression @code{(+ 1 2)} on the @samp{foo} server, and returns @code{3}. (If there is no server with that name, an error is signaled.) Currently, this feature is mainly useful for developers. If your operating system’s desktop environment is @url{https://www.freedesktop.org/wiki/Specifications/,,freedesktop.org-compatible} (which is true of most GNU/Linux and other recent Unix-like GUIs), you may use the @samp{Emacs (Client)} menu entry to connect to an Emacs server with @command{emacsclient}. The daemon starts if not already running. @menu * TCP Emacs server:: Listening to a TCP socket. * Invoking emacsclient:: Connecting to the Emacs server. * emacsclient Options:: Emacs client startup options. @end menu @node TCP Emacs server @subsection TCP Emacs server @cindex TCP Emacs server @vindex server-use-tcp An Emacs server usually listens to connections on a local Unix domain socket. Some operating systems, such as MS-Windows, do not support local sockets; in that case, the server uses TCP sockets instead. In some cases it is useful to have the server listen on a TCP socket even if local sockets are supported, e.g., if you need to contact the Emacs server from a remote machine. You can set @code{server-use-tcp} to non-@code{nil} to have Emacs listen on a TCP socket instead of a local socket. This is the default if your OS does not support local sockets. @vindex server-host @vindex server-port If the Emacs server is set to use TCP, it will by default listen on a random port on the localhost interface. This can be changed to another interface and/or a fixed port using the variables @code{server-host} and @code{server-port}. @vindex server-auth-key A TCP socket is not subject to file system permissions. To retain some control over which users can talk to an Emacs server over TCP sockets, the @command{emacsclient} program must send an authorization key to the server. This key is normally randomly generated by the Emacs server. This is the recommended mode of operation. @findex server-generate-key If needed, you can set the authorization key to a static value by setting the @code{server-auth-key} variable. The key must consist of 64 ASCII printable characters except for space (this means characters from @samp{!} to @samp{~}, or from decimal code 33 to 126). You can use @kbd{M-x server-generate-key} to get a random key. @vindex server-auth-dir @cindex server file When you start a TCP Emacs server, Emacs creates a @dfn{server file} containing the TCP information to be used by @command{emacsclient} to connect to the server. The variable @code{server-auth-dir} specifies the default directory containing the server file; by default, this is @file{~/.emacs.d/server/}. In the absence of a local socket with file permissions, the permissions of this directory determine which users can have their @command{emacsclient} processes talk to the Emacs server. If @code{server-name} is an absolute file name, the server file is created where specified by that file name. @vindex EMACS_SERVER_FILE@r{, environment variable} To tell @command{emacsclient} to connect to the server over TCP with a specific server file, use the @samp{-f} or @samp{--server-file} option, or set the @env{EMACS_SERVER_FILE} environment variable (@pxref{emacsclient Options}). If @code{server-auth-dir} is set to a non-standard value, or if @code{server-name} is set to an absolute file name, @command{emacsclient} needs an absolute file name to the server file, as the default @code{server-auth-dir} is hard-coded in @command{emacsclient} to be used as the directory for resolving relative filenames. @node Invoking emacsclient @subsection Invoking @code{emacsclient} @cindex @code{emacsclient} invocation The simplest way to use the @command{emacsclient} program is to run the shell command @samp{emacsclient @var{file}}, where @var{file} is a file name. This connects to an Emacs server, and tells that Emacs process to visit @var{file} in one of its existing frames---either a graphical frame, or one in a text terminal (@pxref{Frames}). You can then select that frame to begin editing. If there is no Emacs server, the @command{emacsclient} program halts with an error message (you can prevent this from happening by using the @samp{--alternate-editor=""} option to @command{emacsclient}, @pxref{emacsclient Options}). If the Emacs process has no existing frame---which can happen if it was started as a daemon (@pxref{Emacs Server})---then Emacs opens a frame on the terminal in which you called @command{emacsclient}. You can also force @command{emacsclient} to open a new frame on a graphical display using the @samp{-c} option, or on a text terminal using the @samp{-t} option. @xref{emacsclient Options}. If you are running on a single text terminal, you can switch between @command{emacsclient}'s shell and the Emacs server using one of two methods: (i) run the Emacs server and @command{emacsclient} on different virtual terminals, and switch to the Emacs server's virtual terminal after calling @command{emacsclient}; or (ii) call @command{emacsclient} from within the Emacs server itself, using Shell mode (@pxref{Interactive Shell}) or Term mode (@pxref{Term Mode}); @command{emacsclient} blocks only the subshell under Emacs, and you can still use Emacs to edit the file. @kindex C-x # @findex server-edit When you finish editing @var{file} in the Emacs server, type @kbd{C-x #} (@code{server-edit}) in its buffer. This saves the file and sends a message back to the @command{emacsclient} program, telling it to exit. Programs that use @env{EDITOR} usually wait for the editor---in this case @command{emacsclient}---to exit before doing something else. @findex server-edit-abort If you want to abandon the edit instead, use the @w{@kbd{M-x server-edit-abort}} command. This sends a message back to the @command{emacsclient} program, telling it to exit with abnormal exit status, and doesn't save any buffers. You can also call @command{emacsclient} with multiple file name arguments: @samp{emacsclient @var{file1} @var{file2} ...} tells the Emacs server to visit @var{file1}, @var{file2}, and so forth. Emacs selects the buffer visiting @var{file1}, and buries the other buffers at the bottom of the buffer list (@pxref{Buffers}). The @command{emacsclient} program exits once all the specified files are finished (i.e., once you have typed @kbd{C-x #} in each server buffer). @vindex server-kill-new-buffers @vindex server-temp-file-regexp Finishing with a server buffer also kills the buffer, unless it already existed in the Emacs session before the server was asked to create it. However, if you set @code{server-kill-new-buffers} to @code{nil}, then a different criterion is used: finishing with a server buffer kills it if the file name matches the regular expression @code{server-temp-file-regexp}. This is set up to distinguish certain temporary files. Each @kbd{C-x #} 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 way to tell @command{emacsclient} that you are finished. @vindex server-window If you set the value of the variable @code{server-window} to a window or a frame, @kbd{C-x #} always displays the next server buffer in that window or in that frame. @vindex server-client-instructions When @command{emacsclient} connects, the server will normally output a message that says how to exit the client frame. If @code{server-client-instructions} is set to @code{nil}, this message is inhibited. @node emacsclient Options @subsection @code{emacsclient} Options @cindex @code{emacsclient} options You can pass some optional arguments to the @command{emacsclient} program, such as: @example emacsclient -c +12 @var{file1} +4:3 @var{file2} @end example @noindent The @samp{+@var{line}} or @samp{+@var{line}:@var{column}} arguments specify line numbers, or line and column numbers, for the next file argument. These behave like the command line arguments for Emacs itself. @xref{Action Arguments}. The other optional arguments recognized by @command{emacsclient} are listed below: @table @samp @item -a @var{command} @itemx --alternate-editor=@var{command} Specify a shell command to run if @command{emacsclient} fails to contact Emacs. This is useful when running @code{emacsclient} in a script. The command may include arguments, which may be quoted "like this". Currently, escaping of quotes is not supported. As a special exception, if @var{command} is the empty string, then @command{emacsclient} starts Emacs in daemon mode (as @samp{emacs --daemon}) and then tries connecting again. @cindex @env{ALTERNATE_EDITOR} environment variable The environment variable @env{ALTERNATE_EDITOR} has the same effect as the @samp{-a} option. If both are present, the latter takes precedence. @cindex client frame @item -c @itemx --create-frame Create a new graphical @dfn{client frame}, instead of using an existing Emacs frame. See below for the special behavior of @kbd{C-x C-c} in a client frame. If Emacs cannot create a new graphical frame (e.g., if it cannot connect to the X server), it tries to create a text terminal client frame, as though you had supplied the @samp{-t} option instead. On MS-Windows, a single Emacs session cannot display frames on both graphical and text terminals, nor on multiple text terminals. Thus, if the Emacs server is running on a text terminal, the @samp{-c} option, like the @samp{-t} option, creates a new frame in the server's current text terminal. @xref{Windows Startup}. If you omit a filename argument while supplying the @samp{-c} option, the new frame displays the @file{*scratch*} buffer by default. You can customize this behavior with the variable @code{initial-buffer-choice} (@pxref{Entering Emacs}). @item -r @itemx --reuse-frame Create a new graphical client frame if none exists, otherwise use an existing Emacs frame. @item -F @var{alist} @itemx --frame-parameters=@var{alist} Set the parameters for a newly-created graphical frame (@pxref{Frame Parameters}). @item -d @var{display} @itemx --display=@var{display} Tell Emacs to open the given files on the X display @var{display} (assuming there is more than one X display available). @item -e @itemx --eval Tell Emacs to evaluate some Emacs Lisp code, instead of visiting some files. When this option is given, the arguments to @command{emacsclient} are interpreted as a list of expressions to evaluate, @emph{not} as a list of files to visit. @vindex server-eval-args-left Passing complex Lisp expression via the @option{--eval} command-line option sometimes requires elaborate escaping of characters special to the shell. To avoid this, you can pass arguments to Lisp functions in your expression as additional separate arguments to @command{emacsclient}, and use @var{server-eval-args-left} in the expression to access those arguments. Be careful to have your expression remove the processed arguments from @var{server-eval-args-left} regardless of whether your code succeeds, for example by using @code{pop}, otherwise Emacs will attempt to evaluate those arguments as separate Lisp expressions. @item -f @var{server-file} @itemx --server-file=@var{server-file} Specify a server file (@pxref{TCP Emacs server}) for connecting to an Emacs server via TCP@. Alternatively, you can set the @env{EMACS_SERVER_FILE} environment variable to point to the server file. (The command-line option overrides the environment variable.) An Emacs server usually uses a local socket to listen for connections, but also supports connections over TCP@. To connect to a TCP Emacs server, @command{emacsclient} needs to read a @dfn{server file} containing the connection details of the Emacs server. The name of this file is specified with this option, either as a file name relative to @file{~/.emacs.d/server} or as an absolute file name. @xref{TCP Emacs server}. @item -n @itemx --no-wait Let @command{emacsclient} exit immediately, instead of waiting until all server buffers are finished. You can take as long as you like to edit the server buffers within Emacs, and they are @emph{not} killed when you type @kbd{C-x #} in them. @item -w @itemx --timeout=@var{N} Wait for a response from Emacs for @var{N} seconds before giving up. If there is no response within that time, @command{emacsclient} will display a warning and exit. The default is @samp{0}, which means to wait forever. @item --parent-id=@var{id} Open an @command{emacsclient} frame as a client frame in the parent X window with id @var{id}, via the XEmbed protocol. Currently, this option is mainly useful for developers. @item -q @itemx --quiet Do not let @command{emacsclient} display messages about waiting for Emacs or connecting to remote server sockets. @item -u @itemx --suppress-output Do not let @command{emacsclient} display results returned from the server. Mostly useful in combination with @samp{-e} when the evaluation performed is for side-effect rather than result. @item -s @var{server-name} @itemx --socket-name=@var{server-name} Connect to the Emacs server named @var{server-name}. (This option is not supported on MS-Windows.) The server name is given by the variable @code{server-name} on the Emacs server. If this option is omitted, @command{emacsclient} connects to the default socket. If you set @code{server-name} of the Emacs server to an absolute file name, give the same absolute file name as @var{server-name} to this option to instruct @command{emacsclient} to connect to that server. You need to use this option if you started Emacs as daemon (@pxref{Initial Options}) and specified the name for the server started by the daemon. Alternatively, you can set the @env{EMACS_SOCKET_NAME} environment variable to point to the server socket. (The command-line option overrides the environment variable.) @item -t @itemx --tty @itemx -nw @itemx --no-window-system Create a new client frame on the current text terminal, instead of using an existing Emacs frame. This behaves just like the @samp{-c} option, described above, except that it creates a text terminal frame (@pxref{Text Terminals}). On MS-Windows, @samp{-t} behaves just like @samp{-c} if the Emacs server is using the graphical display, but if the Emacs server is running on a text terminal, it creates a new frame in the current text terminal. @item -T @var{tramp-prefix} @itemx --tramp=@var{tramp-prefix} Set the prefix to add to filenames for Emacs to locate files on remote machines (@pxref{Remote Files}) using TRAMP (@pxref{Top, The Tramp Manual,, tramp, The Tramp Manual}). This is mostly useful in combination with using the Emacs server from a remote host. By ssh-forwarding the listening socket, or ssh-forwarding the listening port @pxref{TCP Emacs server} and making the @var{server-file} available on a remote machine, programs on the remote machine can use @command{emacsclient} as the value for the @env{EDITOR} and similar environment variables, but instead of talking to an Emacs server on the remote machine, the files will be visited in the local Emacs session using TRAMP. @vindex EMACSCLIENT_TRAMP@r{, environment variable} Setting the environment variable @env{EMACSCLIENT_TRAMP} has the same effect as using the @samp{-T} option. If both are specified, the command-line option takes precedence. For example, assume two hosts, @samp{local} and @samp{remote}. @example local$ ssh -R "/home/%r/.emacs.socket":"$@{XDG_RUNTIME_DIR:-$@{TMPDIR:-/tmp@}/emacs%i@}$@{XDG_RUNTIME_DIR:+/emacs@}/server" remote remote$ export EMACS_SOCKET_NAME=$HOME/.emacs.socket remote$ export EMACSCLIENT_TRAMP=/ssh:remote: remote$ export EDITOR=emacsclient remote$ $EDITOR /tmp/foo.txt #Should open in local emacs. @end example If you are using a platform where @command{emacsclient} does not use Unix domain sockets (i.e., MS-Windows), or your SSH implementation is not able to forward them (e.g., OpenSSH before version 6.7), you can forward a TCP port instead. In this example, assume that the local Emacs listens on tcp port 12345. Assume further that @file{/home} is on a shared file system, so that the server file @file{~/.emacs.d/server/server} is readable on both hosts. @example local$ ssh -R12345:localhost:12345 remote remote$ export EMACS_SERVER_FILE=server remote$ export EMACSCLIENT_TRAMP=/ssh:remote: remote$ export EDITOR=emacsclient remote$ $EDITOR /tmp/foo.txt #Should open in local emacs. @end example @item -V @itemx --version Print version information and exit. @item -H @itemx --help Print usage information message and exit. @end table The new graphical or text terminal frames created by the @samp{-c} or @samp{-t} options are considered @dfn{client frames}. Any new frame that you create from a client frame is also considered a client frame. If you type @kbd{C-x C-c} (@code{save-buffers-kill-terminal}) in a client frame, that command does not kill the Emacs session as it normally does (@pxref{Exiting}). Instead, Emacs deletes the client frame; furthermore, if the client frame has an @command{emacsclient} waiting to regain control (i.e., if you did not supply the @samp{-n} option), Emacs deletes all other frames of the same client, and marks the client's server buffers as finished, as though you had typed @kbd{C-x #} in all of them. If it so happens that there are no remaining frames after the client frame(s) are deleted, the Emacs session exits. As an exception, when Emacs is started as a daemon, all frames are considered client frames, and @kbd{C-x C-c} never kills Emacs. To kill a daemon session, type @kbd{M-x kill-emacs}. Note that the @samp{-t} and @samp{-n} options are contradictory: @samp{-t} says to take control of the current text terminal to create a new client frame, while @samp{-n} says not to take control of the text terminal. If you supply both options, Emacs visits the specified files(s) in an existing frame rather than a new client frame, negating the effect of @samp{-t}. @node Printing @section Printing Hard Copies @cindex hardcopy @cindex printing Emacs provides commands for printing hardcopies of either an entire buffer or part of one. You can invoke the printing commands directly, as detailed below, or using the @samp{File} menu on the menu bar. @findex htmlfontify-buffer Aside from the commands described in this section, you can also print hardcopies from Dired (@pxref{Operating on Files}) and the diary (@pxref{Displaying the Diary}). You can also ``print'' an Emacs buffer to HTML with the command @kbd{M-x htmlfontify-buffer}, which converts the current buffer to a HTML file, replacing Emacs faces with CSS-based markup. Furthermore, Org mode allows you to print Org files to a variety of formats, such as PDF (@pxref{Org Mode}). @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 @vindex lpr-commands On most operating systems, the above hardcopy commands submit files for printing by calling the @command{lpr} program. To change the printer program, customize the variable @code{lpr-command}. To specify extra switches to give the printer program, customize the list variable @code{lpr-switches}. Its value should be a list of option strings, each of which should start with @samp{-} (e.g., the option string @code{"-w80"} specifies a line width of 80 columns). The default is the empty list, @code{nil}. @vindex printer-name @vindex lpr-printer-switch To specify the printer to use, set the variable @code{printer-name}. The default, @code{nil}, specifies the default printer. If you set it to a printer name (a string), that name is passed to @command{lpr} with the @samp{-P} switch; if you are not using @command{lpr}, you should specify the switch with @code{lpr-printer-switch}. @vindex lpr-headers-switches @vindex lpr-add-switches 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 @command{lpr}) to the printer program: @code{nil} means don't add them (this should be the value if your printer program is not compatible with @command{lpr}). @menu * PostScript:: Printing buffers or regions as PostScript. * PostScript Variables:: Customizing the PostScript printing commands. * Printing Package:: An optional advanced printing interface. @end menu @node PostScript @subsection 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 and spool a PostScript image for the current buffer text. @item M-x ps-spool-region Generate and spool a PostScript image for the current region. @item M-x ps-spool-buffer-with-faces Generate and spool a PostScript image for the current buffer, showing the faces used. @item M-x ps-spool-region-with-faces Generate and spool a PostScript image for the current region, showing the faces used. @item M-x ps-despool Send the spooled PostScript to the printer. @item M-x handwrite Generate/print PostScript for the current buffer as if handwritten. @end table @findex ps-print-region @findex ps-print-buffer @findex ps-print-region-with-faces @findex ps-print-buffer-with-faces The @code{ps-print-buffer} and @code{ps-print-region} commands print buffer contents in PostScript form. One command prints the entire buffer; the other, just the region. The commands @code{ps-print-buffer-with-faces} and @code{ps-print-region-with-faces} behave similarly, but use PostScript features to show the faces (fonts and colors) of the buffer text. Interactively, when you use a prefix argument (@kbd{C-u}), these commands prompt the user for a file name, and save the PostScript image in that file instead of sending it to the printer. @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. @findex ps-despool Use the command @code{ps-despool} to send the spooled images to the printer. This command sends the PostScript generated by @samp{-spool-} commands (see commands above) to the printer. With a prefix argument (@kbd{C-u}), it prompts for a file name, and saves the spooled PostScript image in that file instead of sending it to the printer. @findex handwrite @cindex handwriting @kbd{M-x handwrite} is more frivolous. It generates a PostScript rendition of the current buffer as a cursive handwritten document. It can be customized in group @code{handwrite}. This function only supports ISO 8859-1 characters. @node PostScript Variables @subsection 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 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. @cindex color emulation on black-and-white printers @vindex ps-print-color-p If your printer doesn't support colors, you should turn off color processing by setting @code{ps-print-color-p} to @code{nil}. By default, if the display supports colors, Emacs produces hardcopy output with color information; on black-and-white printers, colors are emulated with shades of gray. This might produce barely-readable or even illegible output, even if your screen colors only use shades of gray. @vindex ps-black-white-faces Alternatively, you can set @code{ps-print-color-p} to @code{black-white} to have colors display better on black/white printers. This works by using information in @code{ps-black-white-faces} to express colors by customizable list of shades of gray, augmented by bold and italic face attributes. @vindex ps-use-face-background By default, PostScript printing ignores the background colors of the faces, unless the variable @code{ps-use-face-background} is non-@code{nil}. This is to avoid unwanted interference with the zebra stripes and background image/text. @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 and defaults to 8.5 points. The value of @code{ps-font-size} can also be a cons of 2 floats: one for landscape mode, the other for portrait mode. @vindex ps-multibyte-buffer @cindex Intlfonts for PostScript printing @cindex fonts for PostScript printing Emacs supports more scripts and characters than a typical PostScript printer. Thus, some of the characters in your buffer might not be printable using the fonts built into your printer. You can augment the fonts supplied with the printer with those from the GNU Intlfonts package, or you can instruct Emacs to use Intlfonts exclusively. The variable @code{ps-multibyte-buffer} controls this: the default value, @code{nil}, is appropriate for printing @acronym{ASCII} and Latin-1 characters; a value of @code{non-latin-printer} is for printers which have the fonts for @acronym{ASCII}, Latin-1, Japanese, and Korean characters built into them. A value of @code{bdf-font} arranges for the BDF fonts from the Intlfonts package to be used for @emph{all} characters. Finally, a value of @code{bdf-font-except-latin} instructs the printer to use built-in fonts for @acronym{ASCII} and Latin-1 characters, and Intlfonts BDF fonts for the rest. @vindex bdf-directory-list To be able to use the BDF fonts, Emacs needs to know where to find them. The variable @code{bdf-directory-list} holds the list of directories where Emacs should look for the fonts; the default value includes a single directory @file{/usr/local/share/emacs/fonts/bdf}. Many other customization variables for these commands are defined and described in the Lisp files @file{ps-print.el} and @file{ps-mule.el}. @node Printing Package @subsection Printing Package @cindex Printing package The basic Emacs facilities for printing hardcopy can be extended using the Printing package. This provides an easy-to-use interface for choosing what to print, previewing PostScript files before printing, and setting various printing options such as print headers, landscape or portrait modes, duplex modes, and so forth. On GNU/Linux or Unix systems, the Printing package relies on the @file{gs} and @file{gv} utilities, which are distributed as part of the GhostScript program. On MS-Windows, the @file{gstools} port of Ghostscript can be used. @findex pr-interface To use the Printing package, add @code{(require 'printing)} to your init file (@pxref{Init File}), followed by @code{(pr-update-menus)}. This function replaces the usual printing commands in the menu bar with a @samp{Printing} submenu that contains various printing options. You can also type @kbd{M-x pr-interface @key{RET}}; this creates a @file{*Printing Interface*} buffer, similar to a customization buffer, where you can set the printing options. After selecting what and how to print, you start the print job using the @samp{Print} button (click @kbd{mouse-2} on it, or move point over it and type @key{RET}). For further information on the various options, use the @samp{Interface Help} button. @node Sorting @section Sorting Text @cindex sorting Emacs provides several commands for sorting text in the buffer. All operate on the contents of the region. 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 @samp{A} through @samp{Z} come before lower-case @samp{a}, in accordance with the @acronym{ASCII} character sequence (but @code{sort-fold-case}, described below, can change that). 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 @vindex sort-numeric-base @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.; the default is 1. 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 the 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. By default, numbers are interpreted according to @code{sort-numeric-base}, but numbers beginning with @samp{0x} or @samp{0} are interpreted as hexadecimal and octal, respectively. @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. With a prefix argument, sort in reverse order. See below for more details on this command. @findex reverse-region @item M-x reverse-region Reverse the order of the lines in the region. This is useful for sorting into descending order by fields, 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}. @c Picture Mode documentation @ifnottex @include picture-xtra.texi @end ifnottex @node Editing Binary Files @section Editing Binary Files @cindex Hexl mode @cindex mode, Hexl @cindex editing binary files @cindex hex editing 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. Inserting text always overwrites in Hexl mode. This is to reduce the risk of accidentally spoiling the alignment of data in the file. Ordinary text characters insert themselves (i.e., overwrite with themselves). There are commands for insertion of special characters by their code. Most cursor motion keys, as well as @kbd{C-x C-s}, are bound in Hexl mode to commands that produce the same effect. Here is a list of other important commands special to 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-M-a Move to the beginning of a 512-byte page. @item C-M-e Move to the end of a 512-byte page. @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 @noindent Other Hexl commands let you insert strings (sequences) of binary bytes, move by @code{short}s or @code{int}s, etc.; type @kbd{C-h a hexl- @key{TAB}} for details. Hexl mode can also be used for editing text files. This could come in handy if the text file includes unusual characters or uses unusual encoding (@pxref{Coding Systems}). For this purpose, Hexl commands that insert bytes can also insert @acronym{ASCII} and non-@acronym{ASCII} characters, including multibyte characters. To edit a text file with Hexl, visit the file as usual, and then type @w{@kbd{M-x hexl-mode @key{RET}}} to switch to Hexl mode. You can now insert text characters by typing them. However, inserting multibyte characters requires special care, to avoid the danger of creating invalid multibyte sequences: you should start typing such characters when point is on the first byte of a multibyte sequence in the file. @node Saving Emacs Sessions @section Saving Emacs Sessions @cindex saving sessions @cindex restore session @cindex remember editing session @cindex reload files @cindex desktop configuration You can use the desktop library to save the state of Emacs from one session to another. The saved Emacs @dfn{desktop configuration} includes the buffers, their file names, major modes, buffer positions, window and frame configuration, and some important global variables. @vindex desktop-save-mode @findex desktop-save-mode To enable this feature, use the Customization buffer (@pxref{Easy Customization}) to set @code{desktop-save-mode} to @code{t} for future sessions, or add this line in your init file (@pxref{Init File}): @example (desktop-save-mode 1) @end example @vindex desktop-path @vindex desktop-auto-save-timeout If you turn on @code{desktop-save-mode} in your init file, then when Emacs starts, it looks for a saved desktop in @code{desktop-path} (which defaults to @code{user-emacs-directory} and then your home directory) and uses the first desktop it finds. While Emacs runs with @code{desktop-save-mode} turned on, it by default auto-saves the desktop whenever any of the desktop configuration changes. The variable @code{desktop-auto-save-timeout} determines how frequently Emacs checks for modifications to your desktop. The desktop is also saved when you exit Emacs. @cindex disable restoring of desktop configuration Specify the option @samp{--no-desktop} on the Emacs command line when you don't want it to reload any saved desktop configurations. This turns off @code{desktop-save-mode} for the current session. Starting Emacs with the @samp{--no-init-file} option also disables desktop reloading, since it bypasses the init file, where @code{desktop-save-mode} is usually turned on. @findex desktop-change-dir @findex desktop-revert You can have separate saved desktop configurations in different directories; starting Emacs from a directory where you have a saved desktop configuration will restore that configuration, provided that you customize @code{desktop-path} to prepend @file{.} (the current directory) to the other directories there. You can save the current desktop and reload the one saved in another directory by typing @kbd{M-x desktop-change-dir}. Typing @kbd{M-x desktop-revert} reverts to the previously reloaded desktop. @vindex desktop-load-locked-desktop The file in which Emacs saves the desktop is locked while the session runs, to avoid inadvertently overwriting it from another Emacs session. That lock is normally removed when Emacs exits, but if Emacs or your system crashes, the lock stays, and when you restart Emacs, it will by default ask you whether to use the locked desktop file. You can avoid the question by customizing the variable @code{desktop-load-locked-desktop} to either @code{nil}, which means never load the desktop in this case, or @code{t}, which means load the desktop without asking. You can also customize the variable to the special value @code{check-pid}, which means to load the file if the Emacs process that has locked the desktop is not running on the local machine. This should not be used in circumstances where the locking Emacs might still be running on another machine, which could be the case in multi-user environments where your home directory is mounted remotely using NFS or similar. @cindex desktop restore in daemon mode When Emacs starts in daemon mode, it cannot ask you any questions, so if it finds the desktop file locked, it will not load it, unless @code{desktop-load-locked-desktop} is @code{t}. Note that restoring the desktop in daemon mode is somewhat problematic for other reasons: e.g., the daemon cannot use GUI features, so parameters such as frame position, size, and decorations cannot be restored. For that reason, you may wish to delay restoring the desktop in daemon mode until the first client connects, by calling @code{desktop-read} (see below) in a hook function that you add to @code{server-after-make-frame-hook} (@pxref{Creating Frames,,, elisp, The Emacs Lisp Reference Manual}). @findex desktop-save @findex desktop-read Whenever you want, you can use the command @kbd{M-x desktop-save} to force immediate saving of the current desktop. This is useful either if you do not want to use the automatic desktop restoration, and thus don't turn on @code{desktop-save-mode}, or when you have made significant changes to the desktop, and want to make sure the configuration doesn't get lost if Emacs or your system crashes. You can use @kbd{M-x desktop-read} to restore a previously-saved desktop if the current Emacs session didn't load any desktop yet. @vindex desktop-restore-frames By default, the desktop tries to save and restore the frame and window configuration. To disable this, set @code{desktop-restore-frames} to @code{nil}. (See that variable's documentation for some related options that you can customize to fine-tune this behavior.) @vindex frameset-filter-alist When the desktop restores the frame and window configuration, it uses the recorded values of frame parameters, disregarding any settings for those parameters you have in your init file (@pxref{Init File}). This means that frame parameters such as fonts and faces for the restored frames will come from the desktop file, where they were saved when you exited your previous Emacs session; any settings for those parameters in your init file will be ignored. To disable this, customize the value of @code{frameset-filter-alist} to filter out the frame parameters you don't want to be restored; they will then be set according to your customizations in the init file. @vindex desktop-files-not-to-save @vindex remote-file-name-access-timeout@r{, and desktop restoring} Information about buffers visiting remote files is not saved by default. Customize the variable @code{desktop-files-not-to-save} to change this. In this case, you might also consider customizing @code{remote-file-name-access-timeout}, which is the number of seconds after which buffer restoration of a remote file is stopped. This prevents Emacs from being blocked when restoring sessions that visited remote files. @vindex desktop-restore-eager By default, all the buffers in the desktop are restored in one go. However, this may be slow if there are a lot of buffers in the desktop. You can specify the maximum number of buffers to restore immediately with the variable @code{desktop-restore-eager}; the remaining buffers are restored lazily, when Emacs is idle. @findex desktop-clear @vindex desktop-globals-to-clear @vindex desktop-clear-preserve-buffers-regexp Type @kbd{M-x desktop-clear} to empty the Emacs desktop; this can be useful, for example, if you want to switch to another desktop by invoking @kbd{M-x desktop-read} next. The @code{desktop-clear} command kills all buffers except for internal ones, and clears the global variables listed in @code{desktop-globals-to-clear}. If you want it to preserve certain buffers, customize the variable @code{desktop-clear-preserve-buffers-regexp}, whose value is a regular expression matching the names of buffers not to kill. @vindex desktop-globals-to-save If you want to save minibuffer history from one session to another, use the @code{savehist} library. You can also save selected minibuffer-history variables as part of @code{desktop-save-mode} if you add those variables to the value of @code{desktop-globals-to-save}. @node Recursive Edit @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}. @xref{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. It also exits the minibuffer, if it is active. 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 Hyperlinking @section Hyperlinking and Web Navigation Features The following subsections describe convenience features for handling URLs and other types of links occurring in Emacs buffer text. @menu * EWW:: A web browser in Emacs. * Embedded WebKit Widgets:: Embedding browser widgets in Emacs buffers. * Browse-URL:: Following URLs. * Goto Address mode:: Activating URLs. * FFAP:: Finding files etc. at point. @end menu @node EWW @subsection Web Browsing with EWW @findex eww @findex eww-open-file @dfn{EWW}, the Emacs Web Wowser, is a web browser package for Emacs. It allows browsing URLs within an Emacs buffer. The command @kbd{M-x eww} will open a URL or search the web. You can open a file using the command @kbd{M-x eww-open-file}. You can use EWW as the web browser for @code{browse-url}, @pxref{Browse-URL}. For full details, @pxref{Top, EWW,, eww, The Emacs Web Wowser Manual}. @node Embedded WebKit Widgets @subsection Embedded WebKit Widgets @cindex xwidget @cindex webkit widgets @cindex embedded widgets @findex xwidget-webkit-browse-url @findex xwidget-webkit-mode @cindex Xwidget-WebKit mode If Emacs was compiled with the appropriate support packages, it is able to show browser widgets in its buffers. The command @kbd{M-x xwidget-webkit-browse-url} asks for a URL to display in the browser widget. The URL normally defaults to the URL at or before point, but if there is an active region (@pxref{Mark}), the default URL comes from the region instead, after removing any whitespace from it. The command then creates a new buffer with the embedded browser showing the specified URL@. The buffer is put in the Xwidget-WebKit mode (similar to Image mode, @pxref{Image Mode}), which provides one-key commands for scrolling the widget, changing its size, and reloading it. Type @w{@kbd{C-h b}} in that buffer to see the key bindings. @findex xwidget-webkit-edit-mode @cindex xwidget-webkit-edit-mode By default, typing a self-inserting character inside an xwidget webkit buffer will do nothing, or trigger some special action. To make those characters and other common editing keys insert themselves when pressed, you can enable @code{xwidget-webkit-edit-mode}, which redefines them to be passed through to the WebKit xwidget. You can also enable @code{xwidget-webkit-edit-mode} by typing @kbd{e} inside the xwidget webkit buffer. @findex xwidget-webkit-isearch-mode @cindex searching in webkit buffers @code{xwidget-webkit-isearch-mode} is a minor mode that behaves similarly to incremental search (@pxref{Incremental Search}), but operates on the contents of a WebKit widget instead of the current buffer. It is bound to @kbd{C-s} and @kbd{C-r} inside xwidget-webkit buffers. When it is invoked by @kbd{C-r}, the initial search will be performed in reverse direction. Typing any self-inserting character will cause the character to be inserted into the current search query. Typing @kbd{C-s} will cause the WebKit widget to display the next search result, while typing @kbd{C-r} will cause it to display the previous one. To leave incremental search, you can type @kbd{C-g}. @findex xwidget-webkit-browse-history @cindex history of webkit buffers The command @code{xwidget-webkit-browse-history} displays a buffer containing a list of pages previously loaded by the current WebKit buffer, and lets you navigate to those pages by hitting @kbd{RET}. It is bound to @kbd{H}. @vindex xwidget-webkit-disable-javascript @cindex disabling javascript in webkit buffers JavaScript is enabled by default inside WebKit buffers, which could be undesirable, as Web sites often use it to track your online activity. You can disable JavaScript in WebKit buffers by customizing the variable @code{xwidget-webkit-disable-javascript} to a non-@code{nil} value. You must kill all WebKit buffers for this setting to take effect, after it is changed. @node Browse-URL @subsection Following URLs @cindex World Wide Web @cindex Web @findex browse-url @findex browse-url-at-point @findex browse-url-at-mouse @cindex Browse-URL @cindex URLs @table @kbd @item M-x browse-url @key{RET} @var{url} @key{RET} Load a URL into a Web browser. @end table The Browse-URL package allows you to easily follow URLs from within Emacs. Most URLs are followed by invoking a web browser; @samp{mailto:} URLs are followed by invoking the @code{compose-mail} Emacs command to send mail to the specified address (@pxref{Sending Mail}). The command @kbd{M-x browse-url} prompts for a URL, and follows it. If point is located near a plausible URL, that URL is offered as the default. The Browse-URL package also provides other commands which you might like to bind to keys, such as @code{browse-url-at-point} and @code{browse-url-at-mouse}. @vindex browse-url-mailto-function @vindex browse-url-browser-function You can customize Browse-URL's behavior via various options in the @code{browse-url} Customize group. In particular, the option @code{browse-url-mailto-function} lets you define how to follow @samp{mailto:} URLs, while @code{browse-url-browser-function} specifies your default browser. @vindex browse-url-handlers You can define that certain URLs are browsed with other functions by customizing @code{browse-url-handlers}, an alist of regular expressions or predicates paired with functions to browse matching URLs. For more information, view the package commentary by typing @kbd{C-h P browse-url @key{RET}}. @findex url-handler-mode Emacs also has a minor mode that has some support for handling @acronym{URL}s as if they were files. @code{url-handler-mode} is a global minor mode that affects most of the Emacs commands and primitives that deal with file names. After switching on this mode, you can say, for instance, @kbd{C-x C-f https://www.gnu.org/ RET} to see the @acronym{HTML} for that web page, and you can then edit it and save it to a local file, for instance. @node Goto Address mode @subsection Activating URLs @findex goto-address-mode @cindex mode, Goto Address @cindex Goto Address mode @cindex URLs, activating @table @kbd @item M-x goto-address-mode Activate URLs and e-mail addresses in the current buffer. @item M-x global-goto-address-mode Activate @code{goto-address-mode} in all buffers. @end table @kindex C-c RET @r{(Goto Address mode)} @findex goto-address-at-point You can make Emacs mark out URLs specially in the current buffer, by typing @kbd{M-x goto-address-mode}. When this buffer-local minor mode is enabled, it finds all the URLs in the buffer, highlights them, and turns them into clickable buttons. You can follow the URL by typing @kbd{C-c @key{RET}} (@code{goto-address-at-point}) while point is on its text; or by clicking with @kbd{mouse-2}, or by clicking @kbd{mouse-1} quickly (@pxref{Mouse References}). Following a URL is done by calling @code{browse-url} as a subroutine (@pxref{Browse-URL}). It can be useful to add @code{goto-address-mode} to mode hooks and hooks for displaying an incoming message (e.g., @code{rmail-show-message-hook} for Rmail). This is not needed for Gnus or MH-E, which have similar features of their own. @node FFAP @subsection Finding Files and URLs at Point @findex find-file-at-point @findex ffap @findex dired-at-point @findex ffap-next @findex ffap-menu @cindex finding file at point The FFAP package replaces certain key bindings for finding files, such as @kbd{C-x C-f}, with commands that provide more sensible defaults. These commands behave like the ordinary ones when given a prefix argument. Otherwise, they get the default file name or URL from the text around point. If what is found in the buffer has the form of a URL rather than a file name, the commands use @code{browse-url} to view it (@pxref{Browse-URL}). This feature is useful for following references in mail or news buffers, @file{README} files, @file{MANIFEST} files, and so on. For more information, view the package commentary by typing @kbd{C-h P ffap @key{RET}}. @cindex FFAP minor mode @findex ffap-mode To enable FFAP, type @kbd{M-x ffap-bindings}. This makes the following key bindings, and also installs hooks for additional FFAP functionality in Rmail, Gnus and VM article buffers. @table @kbd @item C-x C-f @var{filename} @key{RET} @kindex C-x C-f @r{(FFAP)} Find @var{filename}, guessing a default from text around point (@code{find-file-at-point}). @item C-x C-r @var{filename} @key{RET} @kindex C-x C-r @r{(FFAP)} @code{ffap-read-only}, analogous to @code{find-file-read-only}. @item C-x C-v @var{filename} @key{RET} @kindex C-x C-v @r{(FFAP)} @code{ffap-alternate-file}, analogous to @code{find-alternate-file}. @item C-x d @var{directory} @key{RET} @kindex C-x d @r{(FFAP)} Start Dired on @var{directory}, defaulting to the directory at point (@code{dired-at-point}). @item C-x C-d @var{directory} @key{RET} @code{ffap-list-directory}, analogous to @code{list-directory}. @item C-x 4 f @var{filename} @key{RET} @kindex C-x 4 f @r{(FFAP)} @code{ffap-other-window}, analogous to @code{find-file-other-window}. @item C-x 4 r @var{filename} @key{RET} @code{ffap-read-only-other-window}, analogous to @code{find-file-read-only-other-window}. @item C-x 4 d @var{directory} @key{RET} @code{ffap-dired-other-window}, like @code{dired-other-window}. @item C-x 5 f @var{filename} @key{RET} @kindex C-x 5 f @r{(FFAP)} @code{ffap-other-frame}, analogous to @code{find-file-other-frame}. @item C-x 5 r @var{filename} @key{RET} @code{ffap-read-only-other-frame}, analogous to @code{find-file-read-only-other-frame}. @item C-x 5 d @var{directory} @key{RET} @code{ffap-dired-other-frame}, analogous to @code{dired-other-frame}. @kindex C-x t C-f @r{(FFAP)} @item C-x t C-f @var{filename} @key{return} @code{ffap-other-tab}, analogous to @code{find-file-other-tab}. @item C-x t C-r @var{filename} @key{return} @code{ffap-read-only-other-tab}, analogous to @code{find-file-read-only-other-tab}. @item M-x ffap-next Search buffer for next file name or URL, then find that file or URL. @item S-mouse-3 @kindex S-mouse-3 @r{(FFAP)} @code{ffap-at-mouse} finds the file guessed from text around the position of a mouse click. @item C-S-mouse-3 @kindex C-S-mouse-3 @r{(FFAP)} Display a menu of files and URLs mentioned in current buffer, then find the one you select (@code{ffap-menu}). @end table @node Amusements @section Games and Other Amusements @cindex boredom @cindex games @findex animate-birthday-present @cindex animate The @code{animate} package makes text dance (e.g., @kbd{M-x animate-birthday-present}). @findex blackbox @findex mpuz @findex 5x5 @cindex puzzles @kbd{M-x blackbox}, @kbd{M-x mpuz} and @kbd{M-x 5x5} are 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. The aim of @code{5x5} is to fill in all the squares. @findex bubbles @cindex bubbles @kbd{M-x bubbles} is a game in which the object is to remove as many bubbles as you can in the smallest number of moves. @findex decipher @cindex ciphers @cindex cryptanalysis @kbd{M-x decipher} helps you to cryptanalyze a buffer which is encrypted in a simple monoalphabetic substitution cipher. @findex dissociated-press @kbd{M-x dissociated-press} scrambles the text in the current Emacs buffer, word by word or character by character, writing its output to a buffer named @file{*Dissociation*}. A positive argument 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. Dissociated Press produces results fairly like those of a Markov chain, but is however, an independent, ignoriginal invention; it techniquitously copies several consecutive characters from the sample text between random jumps, unlike a Markov chain which would jump randomly after each word or character. Keep dissociwords out of your documentation, if you want it to be well userenced and properbose. @findex dunnet @cindex dunnet @kbd{M-x dunnet} runs a text-based adventure game. @findex gomoku @cindex Go Moku If you want a little more personal involvement, try @kbd{M-x gomoku}, which plays the game Go Moku with you. @cindex tower of Hanoi @findex 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. @findex life @cindex Life @kbd{M-x life} runs Conway's Game of Life cellular automaton. @findex morse-region @findex unmorse-region @findex nato-region @cindex Morse code @cindex --/---/.-./.../. @kbd{M-x morse-region} converts the text in the region to Morse code; @kbd{M-x unmorse-region} converts it back. @kbd{M-x nato-region} converts the text in the region to NATO phonetic alphabet; @kbd{M-x denato-region} converts it back. @findex pong @cindex Pong game @findex tetris @cindex Tetris @findex snake @cindex Snake @kbd{M-x pong}, @kbd{M-x snake} and @kbd{M-x tetris} are implementations of the well-known Pong, Snake and Tetris games. @findex solitaire @cindex solitaire @kbd{M-x solitaire} plays a game of solitaire in which you jump pegs across other pegs. @findex zone @cindex zone The command @kbd{M-x zone} plays games with the display when Emacs is idle. @findex butterfly @cindex butterfly ``Real Programmers'' deploy @kbd{M-x butterfly}, which uses butterflies to flip a bit on the drive platter, see @uref{https://xkcd.com/378}. @findex doctor @cindex Eliza Finally, if you find yourself frustrated, try describing your problems to the famous psychotherapist Eliza. Just do @kbd{M-x doctor}. End each input by typing @key{RET} twice. @ifnottex @lowersections @end ifnottex