This is ../info/xemacs.info, produced by makeinfo version 4.0 from xemacs/xemacs.texi. INFO-DIR-SECTION XEmacs Editor START-INFO-DIR-ENTRY * XEmacs: (xemacs). XEmacs Editor. END-INFO-DIR-ENTRY This file documents the XEmacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. Copyright (C) 1991, 1992, 1993, 1994 Lucid, Inc. Copyright (C) 1993, 1994 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the author instead of in the original English.  File: xemacs.info, Node: Scrolling, Next: Horizontal Scrolling, Prev: Display, Up: Display Scrolling ========= If a buffer contains text that is too large to fit entirely within the window that is displaying the buffer, XEmacs shows a contiguous section of the text. The section shown always contains point. "Scrolling" means moving text up or down in the window so that different parts of the text are visible. Scrolling forward means that text moves up, and new text appears at the bottom. Scrolling backward moves text down and new text appears at the top. Scrolling happens automatically if you move point past the bottom or top of the window. You can also explicitly request scrolling with the commands in this section. `C-l' Clear frame and redisplay, scrolling the selected window to center point vertically within it (`recenter'). `C-v' `pgdn' `next' Scroll forward (a windowful or a specified number of lines) (`scroll-up'). `M-v' `pgup' `prior' Scroll backward (`scroll-down'). `ARG C-l' Scroll so point is on line ARG (`recenter'). The most basic scrolling command is `C-l' (`recenter') with no argument. It clears the entire frame and redisplays all windows. In addition, it scrolls the selected window so that point is halfway down from the top of the window. The scrolling commands `C-v' and `M-v' let you move all the text in the window up or down a few lines. `C-v' (`scroll-up') with an argument shows you that many more lines at the bottom of the window, moving the text and point up together as `C-l' might. `C-v' with a negative argument shows you more lines at the top of the window. `Meta-v' (`scroll-down') is like `C-v', but moves in the opposite direction. To read the buffer a windowful at a time, use `C-v' with no argument. `C-v' takes the last two lines at the bottom of the window and puts them at the top, followed by nearly a whole windowful of lines not previously visible. Point moves to the new top of the window if it was in the text scrolled off the top. `M-v' with no argument moves backward with similar overlap. The number of lines of overlap across a `C-v' or `M-v' is controlled by the variable `next-screen-context-lines'; by default, it is two. Another way to scroll is using `C-l' with a numeric argument. `C-l' does not clear the frame when given an argument; it only scrolls the selected window. With a positive argument N, `C-l' repositions text to put point N lines down from the top. An argument of zero puts point on the very top line. Point does not move with respect to the text; rather, the text and point move rigidly on the frame. `C-l' with a negative argument puts point that many lines from the bottom of the window. For example, `C-u - 1 C-l' puts point on the bottom line, and `C-u - 5 C-l' puts it five lines from the bottom. Just `C-u' as argument, as in `C-u C-l', scrolls point to the center of the frame. Scrolling happens automatically if point has moved out of the visible portion of the text when it is time to display. Usually scrolling is done to put point vertically centered within the window. However, if the variable `scroll-step' has a non-zero value, an attempt is made to scroll the buffer by that many lines; if that is enough to bring point back into visibility, that is what happens. Scrolling happens automatically if point has moved out of the visible portion of the text when it is time to display. Usually scrolling is done to put point vertically centered within the window. However, if the variable `scroll-step' has a non-zero value, an attempt is made to scroll the buffer by that many lines; if that is enough to bring point back into visibility, that is what happens. If you set `scroll-step' to a small value because you want to use arrow keys to scroll the screen without recentering, the redisplay preemption will likely make XEmacs keep recentering the screen when scrolling fast, regardless of `scroll-step'. To prevent this, set `scroll-conservatively' to a small value, which will have the result of overriding the redisplay preemption.  File: xemacs.info, Node: Horizontal Scrolling, Prev: Scrolling, Up: Display Horizontal Scrolling ==================== `C-x <' Scroll text in current window to the left (`scroll-left'). `C-x >' Scroll to the right (`scroll-right'). The text in a window can also be scrolled horizontally. This means that each line of text is shifted sideways in the window, and one or more characters at the beginning of each line are not displayed at all. When a window has been scrolled horizontally in this way, text lines are truncated rather than continued (*note Continuation Lines::), with a `$' appearing in the first column when there is text truncated to the left, and in the last column when there is text truncated to the right. The command `C-x <' (`scroll-left') scrolls the selected window to the left by N columns with argument N. With no argument, it scrolls by almost the full width of the window (two columns less, to be precise). `C-x >' (`scroll-right') scrolls similarly to the right. The window cannot be scrolled any farther to the right once it is displaying normally (with each line starting at the window's left margin); attempting to do so has no effect.  File: xemacs.info, Node: Selective Display, Next: Display Vars, Prev: Display, Up: Display Selective Display ================= XEmacs can hide lines indented more than a certain number of columns (you specify how many columns). This allows you to get an overview of a part of a program. To hide lines, type `C-x $' (`set-selective-display') with a numeric argument N. (*Note Arguments::, for information on giving the argument.) Lines with at least N columns of indentation disappear from the screen. The only indication of their presence are three dots (`...'), which appear at the end of each visible line that is followed by one or more invisible ones. The invisible lines are still present in the buffer, and most editing commands see them as usual, so it is very easy to put point in the middle of invisible text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots. The commands `C-n' and `C-p' move across the invisible lines as if they were not there. To make everything visible again, type `C-x $' with no argument.  File: xemacs.info, Node: Display Vars, Prev: Selective Display, Up: Display Variables Controlling Display ============================= This section contains information for customization only. Beginning users should skip it. When you reenter XEmacs after suspending, XEmacs normally clears the screen and redraws the entire display. On some terminals with more than one page of memory, it is possible to arrange the termcap entry so that the `ti' and `te' strings (output to the terminal when XEmacs is entered and exited, respectively) switch between pages of memory so as to use one page for XEmacs and another page for other output. In that case, you might want to set the variable `no-redraw-on-reenter' to non-`nil' so that XEmacs will assume, when resumed, that the screen page it is using still contains what XEmacs last wrote there. The variable `echo-keystrokes' controls the echoing of multi-character keys; its value is the number of seconds of pause required to cause echoing to start, or zero, meaning don't echo at all. *Note Echo Area::. If the variable `ctl-arrow' is `nil', control characters in the buffer are displayed with octal escape sequences, all except newline and tab. If its value is `t', then control characters will be printed with an up-arrow, for example `^A'. If its value is not `t' and not `nil', then characters whose code is greater than 160 (that is, the space character (32) with its high bit set) will be assumed to be printable, and will be displayed without alteration. This is the default when running under X Windows, since XEmacs assumes an ISO/8859-1 character set (also known as "Latin1"). The `ctl-arrow' variable may also be set to an integer, in which case all characters whose codes are greater than or equal to that value will be assumed to be printable. Altering the value of `ctl-arrow' makes it local to the current buffer; until that time, the default value is in effect. *Note Locals::. Normally, a tab character in the buffer is displayed as whitespace which extends to the next display tab stop position, and display tab stops come at intervals equal to eight spaces. The number of spaces per tab is controlled by the variable `tab-width', which is made local by changing it, just like `ctl-arrow'. Note that how the tab character in the buffer is displayed has nothing to do with the definition of as a command. If you set the variable `selective-display-ellipses' to `nil', the three dots at the end of a line that precedes invisible lines do not appear. There is no visible indication of the invisible lines. This variable becomes local automatically when set.  File: xemacs.info, Node: Search, Next: Fixit, Prev: Display, Up: Top Searching and Replacement ************************* Like other editors, Emacs has commands for searching for occurrences of a string. The principal search command is unusual in that it is "incremental": it begins to search before you have finished typing the search string. There are also non-incremental search commands more like those of other editors. Besides the usual `replace-string' command that finds all occurrences of one string and replaces them with another, Emacs has a fancy replacement command called `query-replace' which asks interactively which occurrences to replace. * Menu: * Incremental Search:: Search happens as you type the string. * Non-Incremental Search:: Specify entire string and then search. * Word Search:: Search for sequence of words. * Regexp Search:: Search for match for a regexp. * Regexps:: Syntax of regular expressions. * Search Case:: To ignore case while searching, or not. * Replace:: Search, and replace some or all matches. * Other Repeating Search:: Operating on all matches for some regexp.  File: xemacs.info, Node: Incremental Search, Next: Non-Incremental Search, Prev: Search, Up: Search Incremental Search ================== An incremental search begins searching as soon as you type the first character of the search string. As you type in the search string, Emacs shows you where the string (as you have typed it so far) is found. When you have typed enough characters to identify the place you want, you can stop. Depending on what you do next, you may or may not need to terminate the search explicitly with a . `C-s' Incremental search forward (`isearch-forward'). `C-r' Incremental search backward (`isearch-backward'). `C-s' starts an incremental search. `C-s' reads characters from the keyboard and positions the cursor at the first occurrence of the characters that you have typed. If you type `C-s' and then `F', the cursor moves right after the first `F'. Type an `O', and see the cursor move to after the first `FO'. After another `O', the cursor is after the first `FOO' after the place where you started the search. Meanwhile, the search string `FOO' has been echoed in the echo area. The echo area display ends with three dots when actual searching is going on. When search is waiting for more input, the three dots are removed. (On slow terminals, the three dots are not displayed.) If you make a mistake in typing the search string, you can erase characters with . Each cancels the last character of the search string. This does not happen until Emacs is ready to read another input character; first it must either find, or fail to find, the character you want to erase. If you do not want to wait for this to happen, use `C-g' as described below. When you are satisfied with the place you have reached, you can type (or ), which stops searching, leaving the cursor where the search brought it. Any command not specially meaningful in searches also stops the search and is then executed. Thus, typing `C-a' exits the search and then moves to the beginning of the line. is necessary only if the next command you want to type is a printing character, , , or another control character that is special within searches (`C-q', `C-w', `C-r', `C-s', or `C-y'). Sometimes you search for `FOO' and find it, but were actually looking for a different occurrence of it. To move to the next occurrence of the search string, type another `C-s'. Do this as often as necessary. If you overshoot, you can cancel some `C-s' characters with . After you exit a search, you can search for the same string again by typing just `C-s C-s': the first `C-s' is the key that invokes incremental search, and the second `C-s' means "search again". If the specified string is not found at all, the echo area displays the text `Failing I-Search'. The cursor is after the place where Emacs found as much of your string as it could. Thus, if you search for `FOOT', and there is no `FOOT', the cursor may be after the `FOO' in `FOOL'. At this point there are several things you can do. If you mistyped the search string, correct it. If you like the place you have found, you can type or some other Emacs command to "accept what the search offered". Or you can type `C-g', which removes from the search string the characters that could not be found (the `T' in `FOOT'), leaving those that were found (the `FOO' in `FOOT'). A second `C-g' at that point cancels the search entirely, returning point to where it was when the search started. If a search is failing and you ask to repeat it by typing another `C-s', it starts again from the beginning of the buffer. Repeating a failing backward search with `C-r' starts again from the end. This is called "wrapping around". `Wrapped' appears in the search prompt once this has happened. The `C-g' "quit" character does special things during searches; just what it does depends on the status of the search. If the search has found what you specified and is waiting for input, `C-g' cancels the entire search. The cursor moves back to where you started the search. If `C-g' is typed when there are characters in the search string that have not been found--because Emacs is still searching for them, or because it has failed to find them--then the search string characters which have not been found are discarded from the search string. The search is now successful and waiting for more input, so a second `C-g' cancels the entire search. To search for a control character such as `C-s' or or , you must quote it by typing `C-q' first. This function of `C-q' is analogous to its meaning as an Emacs command: it causes the following character to be treated the way a graphic character would normally be treated in the same context. To search backwards, you can use `C-r' instead of `C-s' to start the search; `C-r' is the key that runs the command (`isearch-backward') to search backward. You can also use `C-r' to change from searching forward to searching backwards. Do this if a search fails because the place you started was too far down in the file. Repeated `C-r' keeps looking for more occurrences backwards. `C-s' starts going forward again. You can cancel `C-r' in a search with . The characters `C-y' and `C-w' can be used in incremental search to grab text from the buffer into the search string. This makes it convenient to search for another occurrence of text at point. `C-w' copies the word after point as part of the search string, advancing point over that word. Another `C-s' to repeat the search will then search for a string including that word. `C-y' is similar to `C-w' but copies the rest of the current line into the search string. The characters `M-p' and `M-n' can be used in an incremental search to recall things which you have searched for in the past. A list of the last 16 things you have searched for is retained, and `M-p' and `M-n' let you cycle through that ring. The character `M-' does completion on the elements in the search history ring. For example, if you know that you have recently searched for the string `POTATOE', you could type `C-s P O M-'. If you had searched for other strings beginning with `PO' then you would be shown a list of them, and would need to type more to select one. You can change any of the special characters in incremental search via the normal keybinding mechanism: simply add a binding to the `isearch-mode-map'. For example, to make the character `C-b' mean "search backwards" while in isearch-mode, do this: (define-key isearch-mode-map "\C-b" 'isearch-repeat-backward) These are the default bindings of isearch-mode: `DEL' Delete a character from the incremental search string (`isearch-delete-char'). `RET' Exit incremental search (`isearch-exit'). `C-q' Quote special characters for incremental search (`isearch-quote-char'). `C-s' Repeat incremental search forward (`isearch-repeat-forward'). `C-r' Repeat incremental search backward (`isearch-repeat-backward'). `C-y' Pull rest of line from buffer into search string (`isearch-yank-line'). `C-w' Pull next word from buffer into search string (`isearch-yank-word'). `C-g' Cancels input back to what has been found successfully, or aborts the isearch (`isearch-abort'). `M-p' Recall the previous element in the isearch history ring (`isearch-ring-retreat'). `M-n' Recall the next element in the isearch history ring (`isearch-ring-advance'). `M-' Do completion on the elements in the isearch history ring (`isearch-complete'). Any other character which is normally inserted into a buffer when typed is automatically added to the search string in isearch-mode. Slow Terminal Incremental Search -------------------------------- Incremental search on a slow terminal uses a modified style of display that is designed to take less time. Instead of redisplaying the buffer at each place the search gets to, it creates a new single-line window and uses that to display the line the search has found. The single-line window appears as soon as point gets outside of the text that is already on the screen. When the search is terminated, the single-line window is removed. Only at this time the window in which the search was done is redisplayed to show its new value of point. The three dots at the end of the search string, normally used to indicate that searching is going on, are not displayed in slow style display. The slow terminal style of display is used when the terminal baud rate is less than or equal to the value of the variable `search-slow-speed', initially 1200. The number of lines to use in slow terminal search display is controlled by the variable `search-slow-window-lines'. Its normal value is 1.  File: xemacs.info, Node: Non-Incremental Search, Next: Word Search, Prev: Incremental Search, Up: Search Non-Incremental Search ====================== Emacs also has conventional non-incremental search commands, which require you type the entire search string before searching begins. `C-s STRING ' Search for STRING. `C-r STRING ' Search backward for STRING. To do a non-incremental search, first type `C-s ' (or `C-s C-m'). This enters the minibuffer to read the search string. Terminate the string with to start the search. If the string is not found, the search command gets an error. By default, `C-s' invokes incremental search, but if you give it an empty argument, which would otherwise be useless, it invokes non-incremental search. Therefore, `C-s ' invokes non-incremental search. `C-r ' also works this way. Forward and backward non-incremental searches are implemented by the commands `search-forward' and `search-backward'. You can bind these commands to keys. The reason that incremental search is programmed to invoke them as well is that `C-s ' is the traditional sequence of characters used in Emacs to invoke non-incremental search. Non-incremental searches performed using `C-s ' do not call `search-forward' right away. They first check if the next character is `C-w', which requests a word search. *Note Word Search::.  File: xemacs.info, Node: Word Search, Next: Regexp Search, Prev: Non-Incremental Search, Up: Search Word Search =========== Word search looks for a sequence of words without regard to how the words are separated. More precisely, you type a string of many words, using single spaces to separate them, and the string is found even if there are multiple spaces, newlines or other punctuation between the words. Word search is useful in editing documents formatted by text formatters. If you edit while looking at the printed, formatted version, you can't tell where the line breaks are in the source file. Word search, allows you to search without having to know the line breaks. `C-s C-w WORDS ' Search for WORDS, ignoring differences in punctuation. `C-r C-w WORDS ' Search backward for WORDS, ignoring differences in punctuation. Word search is a special case of non-incremental search. It is invoked with `C-s C-w' followed by the search string, which must always be terminated with another . Being non-incremental, this search does not start until the argument is terminated. It works by constructing a regular expression and searching for that. *Note Regexp Search::. You can do a backward word search with `C-r C-w'. Forward and backward word searches are implemented by the commands `word-search-forward' and `word-search-backward'. You can bind these commands to keys. The reason that incremental search is programmed to invoke them as well is that `C-s C-w' is the traditional Emacs sequence of keys for word search.  File: xemacs.info, Node: Regexp Search, Next: Regexps, Prev: Word Search, Up: Search Regular Expression Search ========================= A "regular expression" ("regexp", for short) is a pattern that denotes a (possibly infinite) set of strings. Searching for matches for a regexp is a powerful operation that editors on Unix systems have traditionally offered. To gain a thorough understanding of regular expressions and how to use them to best advantage, we recommend that you study `Mastering Regular Expressions, by Jeffrey E.F. Friedl, O'Reilly and Associates, 1997'. (It's known as the "Hip Owls" book, because of the picture on its cover.) You might also read the manuals to *Note (gawk)Top::, *Note (ed)Top::, `sed', `grep', *Note (perl)Top::, *Note (regex)Top::, *Note (rx)Top::, `pcre', and *Note (flex)Top::, which also make good use of regular expressions. The XEmacs regular expression syntax most closely resembles that of `ed', or `grep', the GNU versions of which all utilize the GNU `regex' library. XEmacs' version of `regex' has recently been extended with some Perl-like capabilities, described in the next section. In XEmacs, you can search for the next match for a regexp either incrementally or not. Incremental search for a regexp is done by typing `M-C-s' (`isearch-forward-regexp'). This command reads a search string incrementally just like `C-s', but it treats the search string as a regexp rather than looking for an exact match against the text in the buffer. Each time you add text to the search string, you make the regexp longer, and the new regexp is searched for. A reverse regexp search command `isearch-backward-regexp' also exists, bound to `M-C-r'. All of the control characters that do special things within an ordinary incremental search have the same functionality in incremental regexp search. Typing `C-s' or `C-r' immediately after starting a search retrieves the last incremental search regexp used: incremental regexp and non-regexp searches have independent defaults. Non-incremental search for a regexp is done by the functions `re-search-forward' and `re-search-backward'. You can invoke them with `M-x' or bind them to keys. You can also call `re-search-forward' by way of incremental regexp search with `M-C-s '; similarly for `re-search-backward' with `M-C-r '.  File: xemacs.info, Node: Regexps, Next: Search Case, Prev: Regexp Search, Up: Search Syntax of Regular Expressions ============================= Regular expressions have a syntax in which a few characters are special constructs and the rest are "ordinary". An ordinary character is a simple regular expression that matches that character and nothing else. The special characters are `.', `*', `+', `?', `[', `]', `^', `$', and `\'; no new special characters will be defined in the future. Any other character appearing in a regular expression is ordinary, unless a `\' precedes it. For example, `f' is not a special character, so it is ordinary, and therefore `f' is a regular expression that matches the string `f' and no other string. (It does _not_ match the string `ff'.) Likewise, `o' is a regular expression that matches only `o'. Any two regular expressions A and B can be concatenated. The result is a regular expression that matches a string if A matches some amount of the beginning of that string and B matches the rest of the string. As a simple example, we can concatenate the regular expressions `f' and `o' to get the regular expression `fo', which matches only the string `fo'. Still trivial. To do something more powerful, you need to use one of the special characters. Here is a list of them: `. (Period)' is a special character that matches any single character except a newline. Using concatenation, we can make regular expressions like `a.b', which matches any three-character string that begins with `a' and ends with `b'. `*' is not a construct by itself; it is a quantifying suffix operator that means to repeat the preceding regular expression as many times as possible. In `fo*', the `*' applies to the `o', so `fo*' matches one `f' followed by any number of `o's. The case of zero `o's is allowed: `fo*' does match `f'. `*' always applies to the _smallest_ possible preceding expression. Thus, `fo*' has a repeating `o', not a repeating `fo'. The matcher processes a `*' construct by matching, immediately, as many repetitions as can be found; it is "greedy". Then it continues with the rest of the pattern. If that fails, backtracking occurs, discarding some of the matches of the `*'-modified construct in case that makes it possible to match the rest of the pattern. For example, in matching `ca*ar' against the string `caaar', the `a*' first tries to match all three `a's; but the rest of the pattern is `ar' and there is only `r' left to match, so this try fails. The next alternative is for `a*' to match only two `a's. With this choice, the rest of the regexp matches successfully. Nested repetition operators can be extremely slow if they specify backtracking loops. For example, it could take hours for the regular expression `\(x+y*\)*a' to match the sequence `xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz'. The slowness is because Emacs must try each imaginable way of grouping the 35 `x''s before concluding that none of them can work. To make sure your regular expressions run fast, check nested repetitions carefully. `+' is a quantifying suffix operator similar to `*' except that the preceding expression must match at least once. It is also "greedy". So, for example, `ca+r' matches the strings `car' and `caaaar' but not the string `cr', whereas `ca*r' matches all three strings. `?' is a quantifying suffix operator similar to `*', except that the preceding expression can match either once or not at all. For example, `ca?r' matches `car' or `cr', but does not match anything else. `*?' works just like `*', except that rather than matching the longest match, it matches the shortest match. `*?' is known as a "non-greedy" quantifier, a regexp construct borrowed from Perl. This construct is very useful for when you want to match the text inside a pair of delimiters. For instance, `/\*.*?\*/' will match C comments in a string. This could not easily be achieved without the use of a non-greedy quantifier. This construct has not been available prior to XEmacs 20.4. It is not available in FSF Emacs. `+?' is the non-greedy version of `+'. `??' is the non-greedy version of `?'. `\{n,m\}' serves as an interval quantifier, analogous to `*' or `+', but specifies that the expression must match at least N times, but no more than M times. This syntax is supported by most Unix regexp utilities, and has been introduced to XEmacs for the version 20.3. Unfortunately, the non-greedy version of this quantifier does not exist currently, although it does in Perl. `[ ... ]' `[' begins a "character set", which is terminated by a `]'. In the simplest case, the characters between the two brackets form the set. Thus, `[ad]' matches either one `a' or one `d', and `[ad]*' matches any string composed of just `a's and `d's (including the empty string), from which it follows that `c[ad]*r' matches `cr', `car', `cdr', `caddaar', etc. The usual regular expression special characters are not special inside a character set. A completely different set of special characters exists inside character sets: `]', `-' and `^'. `-' is used for ranges of characters. To write a range, write two characters with a `-' between them. Thus, `[a-z]' matches any lower case letter. Ranges may be intermixed freely with individual characters, as in `[a-z$%.]', which matches any lower case letter or `$', `%', or a period. To include a `]' in a character set, make it the first character. For example, `[]a]' matches `]' or `a'. To include a `-', write `-' as the first character in the set, or put it immediately after a range. (You can replace one individual character C with the range `C-C' to make a place to put the `-'.) There is no way to write a set containing just `-' and `]'. To include `^' in a set, put it anywhere but at the beginning of the set. `[^ ... ]' `[^' begins a "complement character set", which matches any character except the ones specified. Thus, `[^a-z0-9A-Z]' matches all characters _except_ letters and digits. `^' is not special in a character set unless it is the first character. The character following the `^' is treated as if it were first (thus, `-' and `]' are not special there). Note that a complement character set can match a newline, unless newline is mentioned as one of the characters not to match. `^' is a special character that matches the empty string, but only at the beginning of a line in the text being matched. Otherwise it fails to match anything. Thus, `^foo' matches a `foo' that occurs at the beginning of a line. When matching a string instead of a buffer, `^' matches at the beginning of the string or after a newline character `\n'. `$' is similar to `^' but matches only at the end of a line. Thus, `x+$' matches a string of one `x' or more at the end of a line. When matching a string instead of a buffer, `$' matches at the end of the string or before a newline character `\n'. `\' has two functions: it quotes the special characters (including `\'), and it introduces additional special constructs. Because `\' quotes special characters, `\$' is a regular expression that matches only `$', and `\[' is a regular expression that matches only `[', and so on. *Please note:* For historical compatibility, special characters are treated as ordinary ones if they are in contexts where their special meanings make no sense. For example, `*foo' treats `*' as ordinary since there is no preceding expression on which the `*' can act. It is poor practice to depend on this behavior; quote the special character anyway, regardless of where it appears. For the most part, `\' followed by any character matches only that character. However, there are several exceptions: characters that, when preceded by `\', are special constructs. Such characters are always ordinary when encountered on their own. Here is a table of `\' constructs: `\|' specifies an alternative. Two regular expressions A and B with `\|' in between form an expression that matches anything that either A or B matches. Thus, `foo\|bar' matches either `foo' or `bar' but no other string. `\|' applies to the largest possible surrounding expressions. Only a surrounding `\( ... \)' grouping can limit the grouping power of `\|'. Full backtracking capability exists to handle multiple uses of `\|'. `\( ... \)' is a grouping construct that serves three purposes: 1. To enclose a set of `\|' alternatives for other operations. Thus, `\(foo\|bar\)x' matches either `foox' or `barx'. 2. To enclose an expression for a suffix operator such as `*' to act on. Thus, `ba\(na\)*' matches `bananana', etc., with any (zero or more) number of `na' strings. 3. To record a matched substring for future reference. This last application is not a consequence of the idea of a parenthetical grouping; it is a separate feature that happens to be assigned as a second meaning to the same `\( ... \)' construct because there is no conflict in practice between the two meanings. Here is an explanation of this feature: `\DIGIT' matches the same text that matched the DIGITth occurrence of a `\( ... \)' construct. In other words, after the end of a `\( ... \)' construct. the matcher remembers the beginning and end of the text matched by that construct. Then, later on in the regular expression, you can use `\' followed by DIGIT to match that same text, whatever it may have been. The strings matching the first nine `\( ... \)' constructs appearing in a regular expression are assigned numbers 1 through 9 in the order that the open parentheses appear in the regular expression. So you can use `\1' through `\9' to refer to the text matched by the corresponding `\( ... \)' constructs. For example, `\(.*\)\1' matches any newline-free string that is composed of two identical halves. The `\(.*\)' matches the first half, which may be anything, but the `\1' that follows must match the same exact text. `\(?: ... \)' is called a "shy" grouping operator, and it is used just like `\( ... \)', except that it does not cause the matched substring to be recorded for future reference. This is useful when you need a lot of grouping `\( ... \)' constructs, but only want to remember one or two - or if you have more than nine groupings and need to use backreferences to refer to the groupings at the end. Using `\(?: ... \)' rather than `\( ... \)' when you don't need the captured substrings ought to speed up your programs some, since it shortens the code path followed by the regular expression engine, as well as the amount of memory allocation and string copying it must do. The actual performance gain to be observed has not been measured or quantified as of this writing. The shy grouping operator has been borrowed from Perl, and has not been available prior to XEmacs 20.3, nor is it available in FSF Emacs. `\w' matches any word-constituent character. The editor syntax table determines which characters these are. *Note Syntax::. `\W' matches any character that is not a word constituent. `\sCODE' matches any character whose syntax is CODE. Here CODE is a character that represents a syntax code: thus, `w' for word constituent, `-' for whitespace, `(' for open parenthesis, etc. *Note Syntax::, for a list of syntax codes and the characters that stand for them. `\SCODE' matches any character whose syntax is not CODE. The following regular expression constructs match the empty string--that is, they don't use up any characters--but whether they match depends on the context. `\`' matches the empty string, but only at the beginning of the buffer or string being matched against. `\'' matches the empty string, but only at the end of the buffer or string being matched against. `\=' matches the empty string, but only at point. (This construct is not defined when matching against a string.) `\b' matches the empty string, but only at the beginning or end of a word. Thus, `\bfoo\b' matches any occurrence of `foo' as a separate word. `\bballs?\b' matches `ball' or `balls' as a separate word. `\B' matches the empty string, but _not_ at the beginning or end of a word. `\<' matches the empty string, but only at the beginning of a word. `\>' matches the empty string, but only at the end of a word. Here is a complicated regexp used by Emacs to recognize the end of a sentence together with any whitespace that follows. It is given in Lisp syntax to enable you to distinguish the spaces from the tab characters. In Lisp syntax, the string constant begins and ends with a double-quote. `\"' stands for a double-quote as part of the regexp, `\\' for a backslash as part of the regexp, `\t' for a tab and `\n' for a newline. "[.?!][]\"')]*\\($\\|\t\\| \\)[ \t\n]*" This regexp contains four parts: a character set matching period, `?' or `!'; a character set matching close-brackets, quotes or parentheses, repeated any number of times; an alternative in backslash-parentheses that matches end-of-line, a tab or two spaces; and a character set matching whitespace characters, repeated any number of times.  File: xemacs.info, Node: Search Case, Next: Replace, Prev: Regexps, Up: Search Searching and Case ================== All searches in Emacs normally ignore the case of the text they are searching through; if you specify searching for `FOO', `Foo' and `foo' are also considered a match. Regexps, and in particular character sets, are included: `[aB]' matches `a' or `A' or `b' or `B'. If you want a case-sensitive search, set the variable `case-fold-search' to `nil'. Then all letters must match exactly, including case. `case-fold-search' is a per-buffer variable; altering it affects only the current buffer, but there is a default value which you can change as well. *Note Locals::. You can also use Case Sensitive Search from the Options menu on your screen.  File: xemacs.info, Node: Replace, Next: Other Repeating Search, Prev: Search Case, Up: Search Replacement Commands ==================== Global search-and-replace operations are not needed as often in Emacs as they are in other editors, but they are available. In addition to the simple `replace-string' command which is like that found in most editors, there is a `query-replace' command which asks you, for each occurrence of a pattern, whether to replace it. The replace commands all replace one string (or regexp) with one replacement string. It is possible to perform several replacements in parallel using the command `expand-region-abbrevs'. *Note Expanding Abbrevs::. * Menu: * Unconditional Replace:: Replacing all matches for a string. * Regexp Replace:: Replacing all matches for a regexp. * Replacement and Case:: How replacements preserve case of letters. * Query Replace:: How to use querying.  File: xemacs.info, Node: Unconditional Replace, Next: Regexp Replace, Prev: Replace, Up: Replace Unconditional Replacement ------------------------- `M-x replace-string STRING NEWSTRING ' Replace every occurrence of STRING with NEWSTRING. `M-x replace-regexp REGEXP NEWSTRING ' Replace every match for REGEXP with NEWSTRING. To replace every instance of `foo' after point with `bar', use the command `M-x replace-string' with the two arguments `foo' and `bar'. Replacement occurs only after point: if you want to cover the whole buffer you must go to the beginning first. By default, all occurrences up to the end of the buffer are replaced. To limit replacement to part of the buffer, narrow to that part of the buffer before doing the replacement (*note Narrowing::). When `replace-string' exits, point is left at the last occurrence replaced. The value of point when the `replace-string' command was issued is remembered on the mark ring; `C-u C-' moves back there. A numeric argument restricts replacement to matches that are surrounded by word boundaries.  File: xemacs.info, Node: Regexp Replace, Next: Replacement and Case, Prev: Unconditional Replace, Up: Replace Regexp Replacement ------------------ `replace-string' replaces exact matches for a single string. The similar command `replace-regexp' replaces any match for a specified pattern. In `replace-regexp', the NEWSTRING need not be constant. It can refer to all or part of what is matched by the REGEXP. `\&' in NEWSTRING stands for the entire text being replaced. `\D' in NEWSTRING, where D is a digit, stands for whatever matched the D'th parenthesized grouping in REGEXP. For example, M-x replace-regexp c[ad]+r \&-safe would replace (for example) `cadr' with `cadr-safe' and `cddr' with `cddr-safe'. M-x replace-regexp \(c[ad]+r\)-safe \1 would perform exactly the opposite replacements. To include a `\' in the text to replace with, you must give `\\'.  File: xemacs.info, Node: Replacement and Case, Next: Query Replace, Prev: Regexp Replace, Up: Replace Replace Commands and Case ------------------------- If the arguments to a replace command are in lower case, the command preserves case when it makes a replacement. Thus, the following command: M-x replace-string foo bar replaces a lower-case `foo' with a lower case `bar', `FOO' with `BAR', and `Foo' with `Bar'. If upper-case letters are used in the second argument, they remain upper-case every time that argument is inserted. If upper-case letters are used in the first argument, the second argument is always substituted exactly as given, with no case conversion. Likewise, if the variable `case-replace' is set to `nil', replacement is done without case conversion. If `case-fold-search' is set to `nil', case is significant in matching occurrences of `foo' to replace; also, case conversion of the replacement string is not done.  File: xemacs.info, Node: Query Replace, Prev: Replacement and Case, Up: Replace Query Replace ------------- `M-% STRING NEWSTRING ' `M-x query-replace STRING NEWSTRING ' Replace some occurrences of STRING with NEWSTRING. `M-x query-replace-regexp REGEXP NEWSTRING ' Replace some matches for REGEXP with NEWSTRING. If you want to change only some of the occurrences of `foo' to `bar', not all of them, you can use `query-replace' instead of `M-%'. This command finds occurrences of `foo' one by one, displays each occurrence, and asks you whether to replace it. A numeric argument to `query-replace' tells it to consider only occurrences that are bounded by word-delimiter characters. Aside from querying, `query-replace' works just like `replace-string', and `query-replace-regexp' works just like `replace-regexp'. The things you can type when you are shown an occurrence of STRING or a match for REGEXP are: `' to replace the occurrence with NEWSTRING. This preserves case, just like `replace-string', provided `case-replace' is non-`nil', as it normally is. `' to skip to the next occurrence without replacing this one. `, (Comma)' to replace this occurrence and display the result. You are then prompted for another input character. However, since the replacement has already been made, and are equivalent. At this point, you can type `C-r' (see below) to alter the replaced text. To undo the replacement, you can type `C-x u'. This exits the `query-replace'. If you want to do further replacement you must use `C-x ESC' to restart (*note Repetition::). `' to exit without doing any more replacements. `. (Period)' to replace this occurrence and then exit. `!' to replace all remaining occurrences without asking again. `^' to go back to the location of the previous occurrence (or what used to be an occurrence), in case you changed it by mistake. This works by popping the mark ring. Only one `^' in a row is allowed, because only one previous replacement location is kept during `query-replace'. `C-r' to enter a recursive editing level, in case the occurrence needs to be edited rather than just replaced with NEWSTRING. When you are done, exit the recursive editing level with `C-M-c' and the next occurrence will be displayed. *Note Recursive Edit::. `C-w' to delete the occurrence, and then enter a recursive editing level as in `C-r'. Use the recursive edit to insert text to replace the deleted occurrence of STRING. When done, exit the recursive editing level with `C-M-c' and the next occurrence will be displayed. `C-l' to redisplay the screen and then give another answer. `C-h' to display a message summarizing these options, then give another answer. If you type any other character, Emacs exits the `query-replace', and executes the character as a command. To restart the `query-replace', use `C-x ', which repeats the `query-replace' because it used the minibuffer to read its arguments. *Note C-x ESC: Repetition.  File: xemacs.info, Node: Other Repeating Search, Prev: Replace, Up: Search Other Search-and-Loop Commands ============================== Here are some other commands that find matches for a regular expression. They all operate from point to the end of the buffer. `M-x occur' Print each line that follows point and contains a match for the specified regexp. A numeric argument specifies the number of context lines to print before and after each matching line; the default is none. The buffer `*Occur*' containing the output serves as a menu for finding occurrences in their original context. Find an occurrence as listed in `*Occur*', position point there, and type `C-c C-c'; this switches to the buffer that was searched and moves point to the original of the same occurrence. `M-x list-matching-lines' Synonym for `M-x occur'. `M-x count-matches' Print the number of matches following point for the specified regexp. `M-x delete-non-matching-lines' Delete each line that follows point and does not contain a match for the specified regexp. `M-x delete-matching-lines' Delete each line that follows point and contains a match for the specified regexp.  File: xemacs.info, Node: Fixit, Next: Files, Prev: Search, Up: Top Commands for Fixing Typos ************************* This chapter describes commands that are especially useful when you catch a mistake in your text just after you have made it, or when you change your mind while composing text on line. * Menu: * Kill Errors:: Commands to kill a batch of recently entered text. * Transpose:: Exchanging two characters, words, lines, lists... * Fixing Case:: Correcting case of last word entered. * Spelling:: Apply spelling checker to a word, or a whole file.  File: xemacs.info, Node: Kill Errors, Next: Transpose, Prev: Fixit, Up: Fixit Killing Your Mistakes ===================== `' Delete last character (`delete-backward-char'). `M-' Kill last word (`backward-kill-word'). `C-x ' Kill to beginning of sentence (`backward-kill-sentence'). The character (`delete-backward-char') is the most important correction command. When used among graphic (self-inserting) characters, it can be thought of as canceling the last character typed. When your mistake is longer than a couple of characters, it might be more convenient to use `M-' or `C-x '. `M-' kills back to the start of the last word, and `C-x ' kills back to the start of the last sentence. `C-x ' is particularly useful when you are thinking of what to write as you type it, in case you change your mind about phrasing. `M-' and `C-x ' save the killed text for `C-y' and `M-y' to retrieve. *Note Yanking::. `M-' is often useful even when you have typed only a few characters wrong, if you know you are confused in your typing and aren't sure exactly what you typed. At such a time, you cannot correct with except by looking at the screen to see what you did. It requires less thought to kill the whole word and start over.