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Summary of Differences between Vi and Xvi Chris Downey John Downey Xvi (pronounced _e_c_k_s-_v_e_e-_e_y_e) is a free, portable, multi-window implementation of the popular UNIX|- editor vi. This document summarises the differences between the ``real'' vi and xvi. These differences are divided into three groups: _u_n_i_m_p_l_e_m_e_n_t_e_d _f_e_a_t_u_r_e_s, _d_i_f_f_e_r_e_n_c_e_s and _e_n_h_a_n_c_e_m_e_n_t_s, and each of these is described in the following sections. _1. _U_n_i_m_p_l_e_m_e_n_t_e_d _F_e_a_t_u_r_e_s _1._1. _E_x _M_o_d_e The main area in which xvi is lacking is vi's _e_x mode, which is not implemented at all (and neither are edit, e, and open modes). However, many of the ex commands are available in xvi as colon commands; the colon commands that have not been implemented are mostly those which offer the same functionality as other commands in vi mode. Specifically, the following ex commands are not implemented, and probably never will be within xvi: _i_n_s_e_r_t _u_n_d_o _e_x _c_h_a_n_g_e _o_p_e_n | _a_p_p_e_n_d _z while these ex commands, although not currently implemented, may be added as colon commands at some time in the future: _a_b_b_r_e_v_i_a_t_e _r_e_c_o_v_e_r _w_r_i_t_e>> _u_n_a_b_b_r_e_v_i_a_t_e _j_o_i_n _________________________ |- UNIX is a trademark of Bell Laboratories. _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _P_a_g_e _1 _2 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _1._2. _V_i _c_o_m_m_a_n_d_s The following vi mode commands are not implemented, although there is no real reason why they shouldn't be: _U = while this one is inappropriate in the context of xvi, since there is no _e_x mode: _Q _1._3. _P_a_r_a_m_e_t_e_r_s The following parameters have not been implemented, and probably won't be: _a_d_a _l_i_s_p _r_e_d_r_a_w _a_d_a_p_a_t_h _m_e_s_g _s_l_o_w_o_p_e_n _a_u_t_o_p_r_i_n_t _m_o_d_e_l_i_n_e _t_e_r_m _b_e_a_u_t_i_f_y _o_p_e_n _t_e_r_s_e _d_i_r_e_c_t_o_r_y _o_p_t_i_m_i_z_e _t_t_y_t_y_p_e _e_d_c_o_m_p_a_t_i_b_l_e _p_r_o_m_p_t _w_i_n_d_o_w _h_a_r_d_t_a_b_s while these parameters may well be implemented at some point: _a_u_t_o_w_r_i_t_e _s_c_r_o_l_l _w_a_r_n _e_r_r_o_r_b_e_l_l_s _s_o_u_r_c_e_a_n_y _w_r_i_t_e_a_n_y _1._4. _M_i_s_c_e_l_l_a_n_e_o_u_s Some features of certain commands do not work as they should. Specifically: o+ Repeat counts before insertions don't work. o+ Appending to named buffers is not yet implemented. o+ Typing ^Q in input mode does not mean the same as ^V; it just inserts a `^Q', assuming it gets as far as the editor at all. o+ Typing ^W in insert mode does not back up one word as in vi. o+ It is not possible to interrupt the editor while it is performing certain operations. If you start off a big global command, you have to wait for it to finish. o+ Flags and counts after colon commands are not supported. _P_a_g_e _2 _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _3 o+ It is not possible to read the output of a system command using :r !_c_o_m_m_a_n_d or to write into a command using :w !_c_o_m_m_a_n_d o+ The :substitute command does not support splitting of lines. o+ Regular expressions, although implemented (see later for more details), do not support the ~ character; also, the \u and \l escape sequences are not supported on the right-hand side of a substitute replacement pattern. o+ The :global command only supports the commands [lps&~d]. o+ Undo does not work properly when applied to macros (either @ or :map); it should undo all the changes made by the macro, but in fact only the last command within the macro is undone. _2. _E_n_h_a_n_c_e_m_e_n_t_s The following extensions are available in xvi. _2._1. _P_a_r_a_m_e_t_e_r _H_a_n_d_l_i_n_g Xvi supports 5 types of parameter: as well as vi's _n_u_m_e_r_i_c, _s_t_r_i_n_g and _b_o_o_l_e_a_n, it also has _e_n_u_m_e_r_a_t_e_d and _l_i_s_t types. The former is used for e.g. format and regextype, while the latter is currently only used for tags. The advantage of the _e_n_u_m_e_r_a_t_e_d type is that if you try to set an illegal value, the set of correct values will be displayed, which is very useful if you have forgotten what the values may be. (Try :set preserve to see an example of this.) _2._2. _W_i_n_d_o_w_s Xvi supports multiple _b_u_f_f_e_r_s and _w_i_n_d_o_w_s. A _b_u_f_f_e_r is the object which holds a file in memory, while a _w_i_n_d_o_w is an area of the screen which shows part of a buffer. Note that every window references a buffer, even if no file is being edited. The following commands are available for operating on buffers and windows: :buffer create a new buffer in a new window; can be followed by a filename, which will be edited in the new buffer. :split create a new window onto the current buffer by splitting the current window in half. The two _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _P_a_g_e _3 _4 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i resulting windows are similar to _v_i_e_w_p_o_r_t_s on to a single editing buffer, in that changes made in one window are reflected in the other one. :close close the current window; will also close the buffer if this is the last window onto it. :x / ZZ close only the current window. If the window is the only one onto the buffer, the buffer will be closed as well, writing it first if it is modified. Hence, for a single window, this command does the same as in vi. g move to the next window. This is normally the window directly below the current one on the screen, or the top window on the screen if the current window is the bottom one. ^W increase the size of the current window (may be given a numeric prefix, default is one line). ^T decrease the size of the current window (may be given a numeric prefix, default is one line). ^O make the current window as large as possible. ^] as for vi, but creates a new buffer window if appropriate (and if autosplit allows). Note that the :quit command quits out of the editor, not out of a window. The :close command is thus the equivalent of :quit for windows. There is no equivalent of :x or ZZ for the whole editor; these have been hijacked for operations on windows. Also the numeric autosplit parameter specifies the maximum number of buffer windows that will be created automatically whenever you either edit more than one file, or use tags to edit a different file. Undo works per buffer, as do marks; yank/put and redo (the . command) work over all buffers, i.e. you can delete from one buffer and put the text into a different buffer. The minrows parameter specifies the minimum number of rows to which a window may be shrunk, including the status line. The default value is 2; 0 and 1 may also be useful. _2._3. _N_a_m_e_d _B_u_f_f_e_r_s As well as the normal named (conjugate) buffers, and the default one named @, several extra buffers named :, /, ? and ! contain the last command lines entered for each of the command types. So for instance, @: will re-execute the last colon command, or you can insert it into your buffer, edit it and then re-execute it (e.g. with _d_d@@). _P_a_g_e _4 _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _5 _2._4. _F_i_l_e _F_o_r_m_a_t_s Xvi will handle different file formats, via the format parameter, which may be set to e.g. "unix", "msdos", etc. This means you can edit MS-DOS files under UNIX, etc. _2._5. _R_e_g_u_l_a_r _E_x_p_r_e_s_s_i_o_n_s Vi's magic parameter is replaced by the regextype parameter, which can take the following values: tags only ^ and $ are significant (used for tags). grep like _g_r_e_p(1), but with _\< and _\> added. egrep like _e_g_r_e_p(1), but with _\< and _\> added. The default is _g_r_e_p. The sections and paragraphs parameters define _e_g_r_e_p-style patterns to search for, rather than _v_i's simplistic (and _t_r_o_f_f- dependent) character pairs. The sentences parameter is also implemented in this fashion, but this is not completely satisfactory at the moment. Note that it is possible to set or unset the magic parameter as in vi; this will simply result in the regextype parameter being set as appropriate. _2._6. _C_o_l_o_u_r Xvi has a minimal amount of support for colours. Basically, there are considered to be four settable colours, each with a numeric parameter to say what its value is: colour colour used for text statuscolour colour used for status lines roscolour as statuscolour, but for readonly files systemcolour colour used for system mode (i.e. subshells and after termination). The actual values of these parameters are system-dependent; on PC versions, they are hardware-dependent video attributes, while on UNIX they are indexes into the entries ``c0'' to ``c9'' in the _t_e_r_m_c_a_p(5) database, which are assumed to be colour-setting escape sequences if they are present. If they are not present, "so" (begin standout mode) and "se" (end standout mode) are used instead. Values of 0 and 1 give normal text, 2 to 9 give standout mode. _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _P_a_g_e _5 _6 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i The default colour for the roscolour parameter will usually involve red if colours are available; this is intended to provide a warning to the user that writing the file may not be possible. The colour values may be entered in decimal, octal or hexadecimal form. This may be convenient for PC versions where the numbers actually represent colour bitmaps; for example, on MS-DOS, :_s_e_t _c_o=_0_x_1_f gives bright white text on a blue background. _2._7. _R_e_p_l_a_c_e _M_o_d_e Xvi's _r_e_p_l_a_c_e mode (entered by the R command) acts more intelligently when you press the return key - it leaves the rest of the current line alone, and just starts replacing text on the next line, starting at the screen column where you first typed R. _2._8. _P_r_e_s_e_r_v_e Rather than use vi's UNIX-specific method for preservation, xvi does periodic preservation of all files currently being edited into a temporary file in the same directory. Xvi tries to do this when you are not typing, so that you won't notice the short delay when the temporary file is written out. Obviously, only changed files are preserved in this way, and the temporary file is normally removed once the real file has been successfully written. As an additional safety measure, when a file is explicitly saved and it appears not to have been preserved recently, it is normally preserved first. This ensures that, even if the operating system crashes while the real file is being created, there should always be at least one recent copy of it in the filesystem. The :preserve command is available as in vi to preserve a specific buffer manually. The level of safety provided by the preservation facility may be configured by changing the values of the _p_r_e_s_e_r_v_e and _p_r_e_s_e_r_v_e_t_i_m_e parameters. The following values are available for _p_r_e_s_e_r_v_e: unsafe Never preserve any buffer before an explicit save. This can be useful on old, slow, floppy-only systems, but is not generally recommended. standard The default value. Only preserve a buffer before an explicit save if it appears not to have been preserved recently. safe Always preserve buffers before they are written. paranoid As for safe, but the preserve file is never removed, even after the file has been successfully written. In all cases, all modified buffers are preserved automatically _P_a_g_e _6 _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _7 after no user events have been received for _p_r_e_s_e_r_v_e_t_i_m_e seconds, if a minimum number of events (currently 60) have been received since the last automatic preservation. This behaviour can be more or less disabled by setting _p_r_e_s_e_r_v_e_t_i_m_e to a very high value. (For example, one of the authors sets it to 600 on the machine he uses at home, which is an 8088-based PC with no hard disk; by way of contrast, on the SparcStation IPX which he uses at work, he sets it to 2.) The names given to preserve files are system-dependent, but are generally of the form "_f_i_l_e_n_a_m_e.tmp", or "_f_i_l_e_n_a_m_e.001" to "_f_i_l_e_n_a_m_e.999". If a preserve file already exists, it will not be overwritten; instead, a new filename will be generated. The -r command line option is not supported. _2._9. _H_e_l_p A primitive help facility is available; the command :help, also mapped to the HELP or F1 keys on many systems, simply creates a new buffer window onto a standard help file. The name of the file which is edited is given by the helpfile string parameter; the default on Unix versions is "/usr/lib/xvi.help". _2._1_0. _S_c_r_o_l_l_i_n_g The _j_u_m_p_s_c_r_o_l_l enumerated parameter controls the editor's behaviour when the cursor moves beyond the limits of the current window. If its value is _o_f_f, and the new position is still reasonably close to the current window, the window will be scrolled so that the new cursor position is at the top or bottom of it. Typically, the window will be scrolled one line at a time as the cursor is moved up or down. This behaviour may not always be desirable; for example, terminals without real scrolling regions may force the editor to do a lot of screen updating, possibly over a slow telephone line or overloaded network. Also, on LCD screens or other displays with a long image persistence, it may make the text more difficult to read. If _j_u_m_p_s_c_r_o_l_l is set to _o_n, scrolling behaviour is modified so that, whenever the cursor moves beyond the limits of the current window, the window is redrawn so as to place the cursor as centrally as possible in it; thus, the window appears to _j_u_m_p to the new position. The default value for _j_u_m_p_s_c_r_o_l_l is auto, which causes the editor to jump instead of scrolling only if it can't scroll the affected window efficiently. In all cases, if the distance from the top or bottom of the window to the new position is more than half the window size, the editor will jump instead of scrolling. Explicit scroll commands (e.g. ^D) are not affected by the jumpscroll parameter. _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _P_a_g_e _7 _8 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _2._1_1. _8-_b_i_t _C_h_a_r_a_c_t_e_r_s Characters with the top bit set may be displayed, although it is not yet possible to have null ('\0') bytes in a file buffer. How the characters are displayed varies between systems; on UNIX, they will be shown as an octal escape sequence, while on MS-DOS, OS/2 and QNX they will be shown as the actual character in the PC character set. This can be controlled by setting the cchars and mchars variables; if these parameters are set, control- and meta-characters (respectively) are shown directly, otherwise they are shown as some sequence of printable characters. You can use the ^_ (control-underscore) command to flip the top bit of the character the cursor is on. This may be useful on systems where it is otherwise impossible to enter 8-bit characters. Tabs are normally displayed as a series of spaces of the appropriate length (according to the tabstops parameter); setting list mode will cause them to be displayed as a control character, as will unsetting the tabs parameter. How the tab character is displayed is then under the control of the cchars parameter. _2._1_2. _M_o_u_s_e _S_u_p_p_o_r_t Some mouse support is available for micro-based systems and workstations. Clicking the mouse button on: any line outside current window changes current window to the one indicated by the mouse (can be used instead of g). top line of any window scrolls window downwards (same as ^Y). bottom line of any window scrolls window upwards (same as ^E). status line of any window shows current file and lines (same as ^G). any text line of any window moves text cursor as near as possible to mouse cursor. Also, windows can be resized by "dragging" the appropriate status line up or down with the mouse. _2._1_3. _M_i_s_c_e_l_l_a_n_e_o_u_s o+ The :wn (write file and edit next) command is provided, as per PC-vi. o+ There is no limit to the number or size of maps which may be defined, nor is there any fixed limit to the number of lines _P_a_g_e _8 _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i _9 in a buffer. o+ The edit parameter controls whether a buffer can be modified. This may be used, together with the _r_e_a_d_o_n_l_y parameter, to implement a nicer version of _v_i_e_w(1) than vi's version, since it won't fool you into thinking that editing the buffer is in any way safe. Be warned: once having set noedit, it is not possible to do a :set edit. It's a one- way street. o+ The timeout parameter is implemented as a numeric value, specifying the number of milliseconds after which to assume that no further input is available to continue with the parsing of a map sequence. This replaces vi's boolean parameter of the same name. o+ The vbell parameter may be used to specify use of a visual, rather than audible, bell, if this is available. o+ The :echo command is available; it simply echoes its arguments, after expansion of % and # characters. o+ In insert and replace modes, ^_A has the same meaning as ^@ in vi, except that it works at any time, not just for the first character. Also, typing ^B_x, where _x is the name of a conjugate buffer, inserts the contents of that buffer into the input stream at that point. The buffer named < always contains the last thing inserted, so that ^_B< is the same as ^_A. _3. _D_i_f_f_e_r_e_n_c_e_s o+ Argument handling is somewhat different; for instance, -_R is not supported, but "-s parameter=value" is, which is much more useful anyway. o+ The _X_V_I_N_I_T environment variable is read instead of _E_X_I_N_I_T. Whilst no files are sourced automatically, users who wish to have a startup file can arrange it very easily. _s_h(1) or _k_s_h(1) users should add this line to their $_H_O_M_E/._p_r_o_f_i_l_e: _X_V_I_N_I_T='_s_o_u_r_c_e _x_v_i-_s_t_a_r_t_u_p-_f_i_l_e'; _e_x_p_o_r_t _X_V_I_N_I_T _c_s_h(1) users should add this to their $_H_O_M_E/._l_o_g_i_n: _s_e_t_e_n_v _X_V_I_N_I_T '_s_o_u_r_c_e _x_v_i-_s_t_a_r_t_u_p-_f_i_l_e' and MS-DOS users should add this to their _a_u_t_o_e_x_e_c._b_a_t: _s_e_t _X_V_I_N_I_T=_s_o_u_r_c_e _x_v_i-_s_t_a_r_t_u_p-_f_i_l_e o+ The tags parameter can be used to specify multiple tags files; these can be separated by either "\ " (backslash space) or "," (comma). _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2 _P_a_g_e _9 _1_0 _S_u_m_m_a_r_y _o_f _D_i_f_f_e_r_e_n_c_e_s _b_e_t_w_e_e_n _V_i _a_n_d _X_v_i o+ Alternate files are handled slightly differently, owing to the presence of buffer and window handling. Essentially, when you close a buffer, its filename is remembered as the alternate file; when you invoke the ^^ or :e # commands, this filename is re-edited. Note that ^^ edits the alternate file in a new buffer window. o+ Hitting the escape key while in the command line does not terminate input; instead, it cancels input, returning the prompt to the beginning of the line. This applies to input for :, /, ? and !. o+ Character-based yanks (or deletes) which span line boundaries are handled correctly (vi gets this wrong). _P_a_g_e _1_0 _2_5_t_h _S_e_p_t_e_m_b_e_r _1_9_9_2