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Mi-Shell Reference Manual Jean Michel Version 2.10 --- 19 August 1992 Introduction: MSH is a ``shell'' which provides a convenient and configurable way to browse through directories and execute commands on files and sets of files by a ``point and shoot'' interface. In contrast to many popular shells, MSH is designed to be particularly useful to a ``power user;'' there is no limit to the number of shortcuts in everyday work she can implement with it: an arbitrary sequence of actions (which is written as an ``MSH script'') may be assigned to each keyboard key, and may depend on the environment (like the file currently pointed to, or its extension, etc...). Of course, MSH is also useful to the average user. Installation: Installation of MSH is simple. You only have to copy MSH.EXE to some directory in your PATH (the directories which are scanned by MS-DOS1 to look for commands), and copy the script files (with extension .MSH) to the same directory. You should then modify the file CONFIG.MSH to indicate your display type, the drives you can access, whether you own The Berkeley Utilities or not, which directory to use for swap files, which editor and browser you want to use, etc... In the file there is a series of lines of the form: | in the line below, replace "c_blue.msh" by the name | of one of the available files describing attributes: | c_mda.msh for monochrome displays | c_pcga.msh for plasma cga displays | c_blue.msh, c_blue1.msh, | c_blue2.msh, c_white.msh various possibilities | for color displays | "c_blue.msh"loaddefs | load blue color | set attributes you should do at it says, e.g. replace c_blue by c_mda if you have a monochrome display. You can define your own colors for MSH; see the appendix on attributes. You now modify the following two lines to define your available drives: "CD" fixed_drives! | define your fixed drives "AB"floppy_drives! | define your floppy drives Similarly, there are these 3 lines in the file: true delta! true berk! true berk_cpmvrm! ---------------------------- 1 MS-DOS is a trademark of Microsoft Corporation If you do not own DELTA, you should replace true by false on the first line and similarly for the second and third if you do not own The Berkeley Utilities. The third line refers to whether you want to use cp, mv and rm or DOS's copy and delete commands for these functions. Finally, there are lines reading: | next line defines the place for "magic" swap files (prog_dir)tmp_dir! | put swap files in same directory as MSH.EXE They specify the directory to use for swap files (see ``Technical highlight no. 2''; used when MSH cannot swap itself to extended memory). This should be a virtual disk or a fast hard disk if you have one. You can set tmp_dir to the empty string ("") to disable swapping to disk. Also, MSH does not provide a built-in editor: the idea is rather to let you use your own. If you do not have one, we include MWE.EXE, a multi-window editor which was developed as a demo of the power of TextLib, a keyboard and screen management C Library distributed by OPENetwork. Similarly, you may use your own browser instead of the built-in one (it will be slower). Of course, you must specify what it is to MSH; so, in CONFIG.MSH you must adapt the lines which say: "mwe "editor! "more "browser! to specify what is your editor and browser; for instance, if you use the mediocre but widespread Wordstar as an editor, and the excellent public-domain browser list by V.Buerg, you may change the above lines to: "ws "editor! "list "browser! Some people have such a good editor, or like their bad one so much, that they will use it as their browser. If your editor or browser does not work with the simple syntax ``edit filename'' or needs extra arguments or parameters after the filename, you can still manage, but you will have to make more complex modifications to CONFIG.MSH. Starting to use the default configuration You can then start MSH just by typing its name. The initial display you get should be: a menu bar at the top above two panels, each containing a display of the files in your current directory, and a list of available drives. All this is completely configurable. We describe here the behavior of MSH when you don't modify the CONFIG.MSH file. We support extended video modes and extended versions of ANSI.SYS. The initial number of lines of a panel will be half the number of total lines of your display(e.g. in 43-lines EGA mode, you will get 21 lines, and 25 in the 50-lines VGA mode instead of the usual 12 in a 25-lines mode; if you have a 132-columns mode you will get 3 panels, and 1 panel in a 40-columns mode). If you have a VGA or EGA card, you can ask MSH to first switch the screen to given number n of lines by giving the option -ln on the command line (the letter ell); for instance msh -l50 asks MSH to switch the screen to 50-line mode before starting. The only values of n currently understood are 25, 43 and 50. The first line of a panel contains a ``pattern'', i.e. a wildcard describing all files in the current directory at the left (e.g. c:\dos\*.*). This is highlighted if the panel is the active panel. At the bottom of a panel are titles for the various columns of the display (Name.ext, size, time) which are highlighted according to the current sort order of the panel. Most of your interaction with MSH is via what you type on the command line. MSH monitors all your keystrokes and decides what to do with them according to your own instructions given via the CONFIG.MSH file (the default configuration sets things so that you can also execute Mi-Shell script instructions directly from the command line with the key AltX). MSH when started always tries to locate the file CONFIG.MSH in the directory where MSH.EXE is located, unless you give it an explicit filename as argument. Two tutorials are on-line when you hit the F1 key to help you get started. The Mi-Shell script language: The configuration of MSH is done by its reading upon start the file CONFIG.MSH. This file is entirely in the MSH script language. Any text following a non-quoted | up to the end of a line is a comment and is ignored. The rest of the text represents instructions in the MSH script language, which is a small Forth-like stack language. As we proceed to describe the language, you can find some useful examples which might help in the section ``quick start at modifying CONFIG.MSH''. The only elements of the language are " which delimits character strings, brackets () which delimit blocks of code, and identifiers which are either words formed from the characters a--z A--Z 0--9 or dot (.) or underscore (_) or dollar ($), or symbols constituted by any other single character. Identifiers represent primitive or user-defined actions (their value is then a block of code), or variables holding character strings, excepted that identifiers starting with a digit are interpreted as character strings as if they were quoted. This is to allow you to write numbers without having to surround them with " (negative numbers like "-1" still have to be quoted). A number is just a particular string whose content is interpretable as a number, and all string operation apply to it; only the arithmetic operations try to interpret their string arguments as numbers. Below are some strings: "abc", "you can put '\"' in a string", 3, "3". The last 2 strings are the same. Below are some identifiers foo, bar, foo_bar, +, !, f31. The language is a stack language like FORTH. The stack contains either character strings or pieces (blocks) of code. In the subsequent descriptions [top] represents the stack top, [top+1] the next element, etc...; push something is the action of pushing something onto the stack. Actions typically read one or more values by popping them from the stack (reading [top] always unstacks it) and return possible results by pushing them on the stack. Some actions are predicate-like: the logical value false is represented by the empty string and true by any other string. The variables false and true are primitives and contain the values "" and "true" respectively. Variables which hold the value true or false will be called boolean in what follows. A character string is written "string" where internal `"' must be quoted by preceding them with \; a character string may span several lines and contain embedded carriage returns. Merely writing a character string pushes it onto the stack. Other identifiers cause their corresponding actions to be executed or their value to be pushed when encountered, except that a sequence of actions (or character string denotations) between `()' is pushed onto the stack as a piece of code instead. A character string or a piece of code may be assigned to an identifier by the action !; e.g., "hello" "H"! or ("")"false"!. In BASIC, this would be written as H = "hello" or as false = "". As a special syntactic convention, the form name! is equivalent to "name"!, so the above examples may be written "hello"H! and ("")false!. We should mention that some variables are ``system variables'': like primitives, they are defined by the system. Some of them can be set by the system as well as the user, and when the user sets them some sytem-defined action results. An example is cwd, the current working directory: setting its value will change the current directory. Also, as a special facility, a variable name beginning with a `$' represents a MS-DOS system variable (such as PATH or COMSPEC); the name must be in uppercase letters to be recognized as a system variable. Assigning to such variables will modify the MS-DOS environment. For instance: $PATH ";\mydir"& $PATH! can be used to modify the PATH. Beware! Only the local copy of the environment owned by MSH will be modified (which means that you will lose your modifications to the environment when leaving MSH; we might provide a way around that in future versions). Some identifiers represent the name of keys, and they are called whenever the corresponding key is pressed. The definable keys and their names are: Function keys F1--F10 ShiftF1--ShiftF10 CtrlF1--CtrlF10 AltF1--AltF10 Control keys CtrlA--CtrlZ Ctrl Break is always a ``break'' key, used to interrupt actions (like get out of loops) ``Alt'' keys AltA--AltZ Alt0--Alt9 AltMinus AltEqual Other keys Home End Left Right PgDn PgUp Down Up Delete Insert BackSpace CtrlHome CtrlEnd CtrlLeft CtrlRight CtrlPgDn CtrlPgUp ShiftDown ShiftUp ShiftLeft ShiftRight Esc Tab BackTab Enter CtrlEnter GreyPlus GreyMinus GreyStar CtrlPrint We now proceed to list the primitive actions, arranged by category. ``Language'' functions: drop Do nothing with [top] (and so just unstack it). dup Duplicate [top]. pick [top] should be some number n. If these are the objects on the stack, starting from the bottom: O(n), O(n-1) ... O(2) O(1) n then after the command the stack will look like: O(n) O(n-1) ... O(2) O(1) O(n) so that 1 pick is equivalent to dup. swap Exchange [top] and [top+1]. roll [top] should be some number n. If objects on top of stack are: O(n), O(n-1) ... O(2) O(1) n after the command they will be: O(n-1) ... O(2) O(1) O(n) so that 2 roll is equivalent to swap. stack_size push as a number the size of the stack. not Push false if [top] is not false, true otherwise. = If [top]=[top+1], push [top] else push false. & push the catenation of [top] and [top+1]. match If [top] matches [top+1], push [top] else push false. cutfirst Cuts [top+1] at [top], that is look for first occurence of string [top] in [top+1], and replace [top] and [top+1] by the part of [top+1] after [top] and the part of [top+1] before [top] (the first may be empty if [top] does not occur in [top+1]). cutlast Like cutfirst, but looks for last occurence of [top] in [top+1]. length push the length of the string [top]. substring extract from [top+2] the substring which starts with the [top+1]th character and ends with the [top]th character, and push it on the stack. if If [top+1] is not false execute [top] else do nothing. ifnot If [top+1] is false execute [top] else do nothing. ifelse If [top+2] is false execute [top] else execute [top+1]. while While execution of [top+1] does not yield false, execute [top]. # Interpret the string [top] as a piece of code and execute it. @ Interpret [top] as an identifier name and replace it by its value. If the value is a piece of code, it is ``uncompiled'' as a character string. isdefined Interpret [top] as an identifier name. Push true if this identifier has been assigned a value, false otherwise. ! Interpret [top] as an identifier name and assign [top+1] to it. + Push [top+1]+[top](interpreted as numbers). - Push [top+1]-[top](interpreted as numbers). * Push [top+1]*[top](interpreted as numbers). / Push [top+1]/[top](interpreted as numbers). < Push true if [top+1]<[top](interpreted as numbers), false otherwise. le Push true if [top+1]<=[top](interpreted as numbers), false otherwise. > Push "true" if [top+1]>[top](interpreted as numbers), false otherwise. ge Push "true" if [top+1]>=[top](interpreted as numbers), false otherwise. debug System variable. If "true", MSH is in ``debug'' mode: before any identifier is executed, a window pops up showing it and the current state of the stack. Panels, menus, windows and mouse support: MSH lets you manipulate several kinds of windows: - Panels, wich are ``directory browsers''. You get two of them in the default configuration. You can move them around, change their attributes, what they display, keys associated to them, etc...These are ``permanent'' windows (they don't disappear when you have finished interacting with them). Permanent windows have numbers (``handles'') associated with them on creation. You may use these numbers to reactivate them (put them in front, ready to receive your keystrokes) later (windows can also be activated by clicking on them with the mouse). - Menus, which are actually general ``hypertext'' windows where fields in the window have actions associated to them. They can be either permanent (they have then numbers associated to them) or temporary (they disappear when you make a choice). - Message, choice and dialog windows. The error windows that the system displays sometimes are of a similar kind. These are temporary windows. A message just displays some text. A dialog window displays some text and waits for your input. A choice window allows you to give a Yes/No answer. A menu could do the same job but this provides a simpler solution. At present, mouse support is limited to actions done on clicks and double clicks. More complex interaction (like drags) are not yet implemented, mostly because of the complexity of the necessary language support to describe them. Panels functions: panel.install Creates a new panel. Only one panel displaying nothing (with number 1) exists at the start. Other panels must be created with this command. One argument must be given on [top], the initial selection pattern of the newly created panel. The current panel is set to the created panel. Other attributes of a panel are set/modified with the following system variables. panel.install pushes one result, the number assigned to the panel. panel.pattern System variable. Represents the `pattern' of the current panel (the selection pattern displayed at the top of the panel). Setting this variable causes the panel to be refreshed by reading from disk the list of files matching the pattern (the father and subdirectories of the current directory are always displayed). As a special facility, this can be assigned a pathname composed of the pathname of a ``.zip'' or ``.arj'' archive file + a pattern. The panel will then display the list of all files inside that archive which correspond to the given pattern. We might add support for other kinds of archives (.lzh, .arc, .zoo) in the future. panel.type Returns the type of the current panel: "" for ordinary panels, ".zip" for a zip archive, ".arj" for an arj archive. panel.sort System variable. Represents the sort order of the current panel. It can be assigned the following values: "N" --- sort the panel by name; "S" --- sort the panel by size; "T" --- sort the panel by date; "E" --- sort the panel by extension. Sorting by extension keeps as a secondary key the previous sort, whatever it was. This is reflected in the highlighted titles at the bottom of the panel.It also means that in the case of an extension sort, the value of panel.sort is actually one of "EN", "ES" or "ET". panel.size Boolean system variable which controls whether the file size is displayed for each file of the current panel. panel.attrs Like panel.size, controls whether the read/write/system-- /hidden attributes are displayed. panel.date Like panel.size, controls whether the last modified date is displayed. panel.time Like panel.size, controls whether the last modified time is displayed. panel.sec Like panel.size, controls whether the last modified time is displayed up to the second. panel.on Boolean system variable. Controls whether the current panel is on. When off, the panel won't be displayed; this is useful to have temporarily an unimpeded view of the screen behind the panel (in addition to the panels, the menu bar can be shut off by uninstalling it; this allows the use of MSH as a ``silent'' background task). panel.rc System variable representing the number of rows and columns of the current panel. When read causes 2 values to be pushed on the stack, first the number of lines and then the number of columns. Similarly it should be set by pushing 2 values on the stack (e.g. 12 40 panel.rc!). panel.startrc System variable. Represents the start row and start column of the current panel (the coordinates of the top left corner). panel.nbfiles push the total number of entries of the current panel. panel.att Function taking 4 arguments representing the video attributes used to display the pattern. They should be given in ANSI format and represent: Normal --- the normal attribute for files in a panel; Current --- the attribute of current name, the file pointed to by the cursor; Selected --- the attribute of selected files; Selected + Current --- the attribute of current name when it happens to be a selected file. current.name push the filename of the entry pointed by the cursor in the current panel (this entry will be called `current name' in the subsequent descriptions). current.isdir push false if current name is not a directory, otherwise push current name (usable as a predicate). current.size push the size (in bytes) of current name. current.time push the last modified time of current name. This time is encoded as an integer by the formula: 2x(seconds+ 32x(minutes+ 64x(hours+ 32x(days+ 32x(months+ 16x(years-1980)))))) current.selected System variable whose value is true or false. Setting it to true selects current name; this highlights it and marks it as ``selected'' which means that current.selected will return true until it is again deselected by setting current.selected to false. current.pos System variable which represents the position of the cursor in the current panel relative to the total number of files. Setting this variable moves the cursor. Values outside of the interval [0,panel.nb- files-1] are mapped to 0 or panel.nbfiles-1. Mouse actions: User-defined mouse actions on a panel are provided as follows: when a mouse event on the panel is detected: - It is activated if it was not active (and panel.on_activate (which should contain an action) is executed). - A two-part name is built and is executed (it should contain an action); - The first part of the name describes the event: LeftClick, LeftDbleClick, RightClick, RightDbleClick, MiddleClick, MiddleDbleClick. - The end part of the name describes the area of the panel where the event occured: N --- On the word ``name'' at the bottom of the panel. E --- On the word ``ext''. S --- On the word ``size''. T --- On the word ``time''. UA --- On the up arrow of the scroll bar. DA --- On the down arrow of the scroll bar. Entry --- On an entry. In that case before executing the name the number of the entry is pushed. Menu functions: The only function proper to menus is menu.install. The way a menu works is by executing actions (pieces of code) associated to fields in its window (``menu selections''). When a menu is active, the cursor keys move between menu selections. The currently highlighted selection is executed when pressing the key Enter or when clicking with the mouse on it. An Escape or clicking outside a selection field quits the menu without any selection being done. The arguments to menu.install describe completely the menu. They are in order: - A list of actions (pieces of code) to be executed for various menu selections. - A string, the text of the menu window. Fields which should operate as menu selections are delimited by % in that string (a % can be put in the menu by doubling it: %%). The fields are matched to actions in order. There should be exactly as many actions as there are fields. - An action which is executed when the menu is exited without any selection made (often the empty action () is suitable). This will occur when the user has activated a menu and then hits ESC. - The coordinates of where to put the upper left corner of the menu window (a "-1" means center the menu in that direction). - Three video attributes given as ANSI strings, to use for displaying the menu: Normal --- the attribute for normal text in the menu window; Selection --- the attribute of a menu selection; Highlighted --- the attribute of the highlighted menu selection; - A string which determines what kind of border the menu should have, and if it should have a title: "" --- no border. ":" --- single line border. "v:" --- single line horizontal / double line vertical border. "h:" --- single line vertical /double line horizontal border. "vh:" --- double line vertical /double line horizontal border. To specify a title add it to the string. For example, "v:Hello" specifies a border with double vertical lines, and single horizontal lines, with 'Hello' as title. - A boolean value wich determines if the menu should be permanent. For a permanent menu, menu.install returns a value, the number assigned to the menu. Permanent Windows Control: Two functions control permanent windows: window.activate Takes as argument the number of the window to activate (panel or menu). An active menu is recognized by having a higlighted selection. An active panel has a highlighted title (and if any files are displayed, current name is highlighted). When activating a panel, the action panel.on_activate is executed. This can be set by the user; in the default configuration what it does is attach to the directory of the panel. An active window is put on top of the others. window.uninstall Takes as argument the number of the window to delete; deletes that window (menu or panel). It is sometimes convenient to give consecutive numbers to a series of panels or menus (the functions next_panel and previous_panel of the default configuration do that). The number given to a newly created window is the first available number, so this can be arranged by just creating the windows consecutively when there has been no deletions. Other Windows: message Display [top] as a message with title [top+1]. This message is left displayed until any key is typed. If the text of the message does not fit on the screen, it is shown screenful by screenful until the end. This can provide a primitive kind of browser. flash Display [top] as a message with title [top+1]. This message is left displayed for the number of milliseconds specified by [top+2]. ok Display [top] as a message and ask confirmation with a Yes No choice. Replaces [top] by false in case of non confirmation (so may be used as a predicate). input Display [top+1] as a message and ask for input in a field of length [top]. The input is pushed on the stack. get_key Display [top] as a message with title [top+1]. Return as a character string the name of the first key typed. alert_att System variable whose value represents (in ANSI format) the color attribute to be used for the message, flash, ok, input and get_key windows. (``alert'' refers to the temporary ``pop-up'' windows of MSH: the ones mentioned above, the warnings and the debug window). Command line: cmd.del Delete the current character in the command line. cmd.pos System variable representing the position of the cursor in the command line (first position is 0). cmd.wordleft Go one word left in the command line. cmd.wordright Go one word right in the command line. cmd.clear Reset to zero the command line. cmd System variable representing the command line. Reading it pushes the command line contents. Setting it writes [top] to the command line; but note that the text is added to the command line where the cursor is in it. Call cmd.clear first to replace the command line contents by new contents. cmd.imode Boolean system variable representing if the command line is in insert mode. Other: read Read the file whose name is [top] and push as a string its contents. write Writes (creates or appends) to the file whose name is [top+1] the string [top]. unlink removes file whose name is [top]. rename renames file whose name is [top+1] to name given by [top]. As for the DOS call, it is possible to rename empty directories, and to move files between directories of the same drive with this call. pushes [top] if successful, false otherwise (e.g. target exists or is in a different drive). copy copies file whose name is [top+1] to name given by [top]. [top] will be overwritten if it exists; copy works across different drives. pushes [top] if successful, false otherwise (e.g. if there was a disk full on the target drive). testfile Returns false if there exists no file with name [top] (which includes the case when a directory with name [top] exists), otherwise pushes the size and last modified time (see format in current.time) of found file. This routine can test if a file exists inside a supported archive type. tempname Creates a temporary file name (a name guaranteed to be a non existent file) in the directory specified by [top]. disk_stats pushes the following information on the drive whose letter is given by [top] (if [top] is "" returns information on current drive): size of a cluster in bytes, number of available clusters, total number of clusters. capture_screenGrabs the contents of the screen as a string and push it on the stack. Takes one boolean argument: if true, makes a graphic capture, encoding video attributes as ansi escape sequences, which allows to redisplay the screen colors using the built-in browser of MSH or MS-DOS's ANSI.SYS. prog_pathname push the pathname of msh.exe. cwd System variable holding the name of the current directory. Setting it attaches to the directory whose name is [top]. linescols System variable holding the total number of lines and columns on the screen. It may be used in conjunction with panel.rc and panel.startrc to program a setup for the screen. execute Send [top] to command.com to be executed. magic System variable. If not false, should specify a directory where MSH will swap itself out of memory before sending any command to MS-DOS for execution if it cannot swap itself to extended memory. As a special convention, if it starts with a `*', it means that swapping to XMS is not desired. See ``Technical highlight no. 2''. page Call the built-in browser. It takes 9 arguments: the name of the file to browse followed by the coordinates of the window for the browser (start row, start column, number of rows, number of colums) and by the list of video attributes to use in the browser: Browser window --- the attribute of the window of the browser. Browser highlight --- the attribute of the status line and of highlighted text in the browser. Empty --- the attribute used when showing empty space in the browser. Tab --- the attribute used when showing tabs in the browser. beep As its name says. time push the current time (in the same format as current.time). timer MSH has a ``timer'' which allows you to do some actions at regular times (which may be used to show a clock) or after some delay (which may be used to set an alarm). [top] should contain the action to do (as a piece of code) and [top+1] a number specifying how many ticks (1=17 sec.) from now this action should be done. To do an action repeatedly, you can write an action which contains a call to set the timer with itself, e.g. after (f 1000 (g)timer)g! a call to g will execute f repeatedly every 1000 ticks. reinit_mouse With some versions of the Microsoft mouse driver and some mouse programs, the mouse driver in MSH may become inactivated when returning from execute. This command reinitializes it (it is not done systematically since it takes 1 to 2 seconds). mouse.click System variable. Holds the interval between the 2 clicks of a mouse double click. By default its value is 3 which means 3 ticks (ie 3 seventeenths of asec.). You may want this to be a bit slower if you are not a Mac user ... quit Quit MSH. A quick start at modifying .MSH files: The first thing you might want to do is add to EXT.MSH instructions to deal with other types of files, recognized by their extension. For instance, I use Knuth's TeX text-processing language, which produces device-independent output files ready to be printed or viewed on the screen; what I want to do when I point to such a file, say foo.dvi, and order MSH to act by pressing the Enter key, is to see what's in it, i.e. call my previewer (called view) with a command such as view foo.dvi. What I did in order to get this is add a line to the series of lines in EXT.MSH which end by extension_something (a typical one: (current.name pager)extension_cfg!) saying: ("view "current.name & execute)extension_dvi! how does this work? When enter is pressed, by a mechanism described below, MSH sees that the command line is empty and decides to execute the identifier extension_xxx where xxx is the extension of current name. It is the line above which gives a definition to the identifier extension_dvi. The final ! is the assignment operator which assigns to extension_dvi what's on the stack. What is there is the code in brackets at the beginning of the line, which has been pushed by the simple virtue of appearing there. What does this code do? First, it pushes the string "view " on the stack, then current name, then catenates [top] and [top+1](operator &); now [top] contains "view foo.dvi"; finally execute sends that string to MS-DOS to be executed; you can watch the whole thing in action by doing the following steps: - Position cursor on foo.dvi and make sure the command line is empty. - Press AltD. If your configuration is the default one, this make MSH enter debug mode. - Press Enter. You will then see the debugger window, which includes a view of the stack. Press s to step through the code of extension_dvi. - Press g (go) when in debug window to leave debug mode. Let us now have a more elaborate text explanation by looking at the code which is executed when pressing Enter. The code is the following lines in KEYBIND.MSH: (cmd (execsave) (act_on_cur) ifelse )Enter! We first put the contents of the command line on the stack (cmd). To understand what happens next you have to notice that the rest consists of 2 blocks of code followed by ifelse. That's a perfectly ordinary if construct, excepted that control structures don't always look nice in reverse polish notation. The way ifelse works is: it expects 2 blocks of code on the stack, and, above that, a value which is false (empty string) or not (non-empty string), and execute one or the other piece of code based on that value. The net effect here is to execute the first piece of code if the command line is non-empty and the second otherwise. The first piece is a definition: (cmd dup cmdlist nl&swap&cmdlist!execute cmd.clear refresh)execsave! it recalls again the command line, duplicates it, uses one copy to store in the circular list of commands cmdlist (where previously typed commands are kept, separated by newlines (the content of the variable nl), for reuse if recalled by the user), and executes the other copy; then clears the command line and calls refresh; this last is itself a definition that you can find in STDDEFS.MSH: (cwd panel.pattern filepart makename panel.pattern!) refresh! The purpose is to refresh the display in the current panel, which might be necessary since the executed command may have destroyed files and/or changed directories. To do that, we first get the current directory's name on the stack, then catenate to it the filename part of the wildcard of the current panel (usually "*.*", but it may be set to something else), then put that as the pattern to select files in the current panel. filepart and makename are also definitions that we don't show here. Let's look now at what we do if the command line is empty: (current.isdir (current.name cwd! refresh) ("extension_" current.name extension&#) ifelse )act_on_cur! We have again an if which tests if current name is a directory or not. current.isdir is a predicate, which as all predicates, by convention returns one of the strings "" (false) or "true". If current name is a directory, we attach to it (current.name cwd!) and refresh. Otherwise, we construct an identifier extension_xxx where xxx is the extension of current name and execute that (#). extension is defined as follows: ("."cutlast swap drop)extension! we cut the name into its part before the "." and after it, and drop the part before it. The other thing I want to do with dvi files is turn them into HP LaserJet output, which I do with dvihp.exe, and that second type of action was associated with the CtrlEnter key. Technical highlight number one: long command lines and The Berkeley Utili- ties: MSH supports (almost) arbitrarily long command lines for programs which recognize its conventions (like The Berkeley Utilities). For instance, if you use the BERK.MSH configuration with cp, mv, rm enabled, and select a lot of files and press F6 (move), you will be asked to confirm a very long command starting with mv, and if you agree mv will correctly move the whole list to the next panel. This is quite advantageous compared to looping on mv of each file, since mv is loaded only once, so the job is done much faster. You may wonder how this is possible, since MS-DOS limits any command line to 127 characters. We do this by a simple trick, which is understood by all The Berkeley Utilities, and which you may make your own programs understand! When the command line is greater than 127 characters, we send only the first 127 to dos; but before that we put the rest in a buffer, preceded by its length as a 2-byte integer, and we add to the MS-DOS environment a variable CMD@=xx, where xx is the adress (as a long decimal integer) of the buffer. The called program has just to check if that variable exists, and if it is the case catenate to its command line the rest of the command line gotten from the address that variable holds. Here is some sample code which does just that; this should help you write your own. #include <stddef.h> #include <stdlib.h> #include <string.h> #include <malloc.h> #include <dos.h> /* this program prints the command line under MSH, adding the extra part at the end of the normal command. This version gets the psp by the TURBO C built-in variable _psp. You have to get it another way if you use another compiler. */ int main() { unsigned cmdlen=*(char far *)((((long)_psp)<<16)+0x80), extralen=0; char *com; int far *extra; char *s=getenv("CMD@"); if(NULL!=s && (extra=(int far *)atol(s))) extralen=*extra; com=malloc(cmdlen+extralen+1); movedata(_psp,0x81, FP_SEG((char far *)com), FP_OFF((char far *)com),cmdlen); if(extralen) { extra++; movedata(FP_SEG(extra),FP_OFF(extra), FP_SEG((char far *)(com+cmdlen)), FP_OFF((char far *)(com+cmdlen)), extralen); } com[cmdlen+extralen]=0; printf("command=<%s>\n",com); return 0; } Technical highlight number two: large memory for your commands: MSH, like a few advanced products, can let your commands use almost all available memory in the system when executing. In order to do that, MSH swaps itself out of memory, writing most of its image to disk or to extended memory (if available) and leaving only a small (8K) image in memory. If you have no (or not enough) extended memory and cannot swap to a virtual disk (in low or expanded memory) this swapping takes some time so you may want to disable it. It is under control of the variable magic: if magic is false (the empty string), its default value, no swapping to disk is done. Otherwise magic must contain the name of the directory to be used for swapping (you may specify ``.'' for the current directory, but we don't recommend it since you will then have problems on a diskette; you should specify some directory on your hard disk or a virtual disk). If you want to run a program which requires the use of all your extended memory (this happens to be the case for Borland's BC++3.0 on my machine which has only 2megs), you may want to disable swapping to XMS: this is done by the special convention of starting the variable magic with a `*'. Command line options: In addition to the -l option explained above, there is another possible option on the command line: -m Disables mouse. If for some reason, you have a mouse but want MSH not to use it, use this option. How to add your own primitives coded in C to msh: Read the file TOOLKIT.DOC which is in the toolkit.