mg - Man Page

• Open a file for editing: mg path/to/file

• Open a file at a specified line number: mg +line_number path/to/file

• Open files in a read-only mode: mg -R path/to/file1 path/to/file2 ...

• Disable ~ backup files while editing: mg -n path/to/file

tldr.sh

mg is intended to be a small, fast, and portable editor for people who can't (or don't want to) run emacs for one reason or another, or are not familiar with the vi(1) editor. It is compatible with emacs because there shouldn't be any reason to learn more editor types than emacs or vi(1).

The options are as follows:

+number

Go to the line specified by number (do not insert a space between the ‘+’ sign and the number). If a negative number is specified, the line number counts backwards from the end of the file i.e. +-1 will be the last line of the file, +-2 will be second last, and so on.

-b file

Turn on batch mode and execute the mg commands found in the specified file and then terminate.

-f mode

Run the mode command for all buffers created from arguments on the command line, including the scratch buffer and all files.

-n

Turn off backup file generation.

-R

Files specified on the command line will be opened read-only.

-u file

Use file as the startup file, instead of the default ~/.mg.

When a file is loaded into mg, it is stored in a buffer. This buffer may be displayed on the screen in more than one window. At present, windows may only be split horizontally, so each window is delineated by a modeline at the bottom. If changes are made to a buffer, it will be reflected in all open windows.

If a file is changed outside mg and its buffer is about to be changed, mg prompts if the change should go ahead (y), not go ahead (n) or if the buffer should be reverted (r) to the latest file on disk.

If a buffer name begins and ends with an asterisk, the buffer is considered throwaway; i.e. the user will not be prompted to save changes when the buffer is killed.

The current cursor location in mg is called the point (or dot). It is possible to define a window-specific region of text by setting a second location, called the mark. The region is the text between point and mark inclusive. Deleting the character at the mark position leaves the mark at the point of deletion.

Note: The point and mark are window-specific in mg, not buffer-specific, as in other emacs flavours.

Backup files have a ‘~’ character appended to the file name and are created in the current working directory by default. Whether to create backup files or not can be toggled with the make-backup-files command. The backup file location can either be in the current working directory, or all backups can be moved to a ~/.mg.d directory where files retain their path name to retain uniqueness. Use the backup-to-home-directory command to alternate between these two locations. Further, if any application creates backup files in /tmp, these can be left with the leave-tmpdir-backups command.

mg supports tag files created by ctags(1), allowing the user to quickly locate various object definitions. Note though that emacs uses etags, not ctags.

mg supports navigating source code using cscope. However, mg requires cscope and cscope-indexer executables to be present in PATH for it to work.

Normal editing commands are very similar to GNU Emacs. In the following examples, C-x means Control-x, and M-x means Meta-x, where the Meta key may be either a special key on the keyboard or the ALT key; otherwise ESC followed by the key X works as well.

For a complete description of mg commands, see MG Commands. To see the active keybindings at any time, type “M-x describe-bindings”.

Commands are invoked by “M-x”, or by binding to a key. Many commands take an optional numerical parameter, n. This parameter is set either by M-<n> (where n is the numerical argument) before the command, or by one or more invocations of the universal argument, usually bound to C-u. When invoked in this manner, the value of the numeric parameter to be passed is displayed in the minibuffer before the M-x. One common use of the parameter is in mode toggles (e.g. make-backup-files). If no parameter is supplied, the mode is toggled to its alternate state. If a positive parameter is supplied, the mode is forced to on. Otherwise, it is forced to off.

apropos

Help Apropos. Prompt the user for a string, open the *help* buffer, and list all mg commands that contain that string.

audible-bell

Toggle the audible system bell.

auto-execute

Register an auto-execute hook; that is, specify a filename pattern (conforming to the shell's filename globbing rules) and an associated function to execute when a file matching the specified pattern is read into a buffer.

auto-fill-mode

Toggle auto-fill mode (sometimes called mail-mode) in the current buffer, where text inserted past the fill column is automatically wrapped to a new line. Can be set globally with set-default-mode.

auto-indent-mode

Toggle indent mode in the current buffer, where indentation is preserved after a newline. Can be set globally with set-default-mode.

back-to-indentation

Move the dot to the first non-whitespace character on the current line.

backup-to-home-directory

Save backup copies to a ~/.mg.d directory instead of working directory. Requires make-backup-files to be on.

backward-char

Move cursor backwards one character.

backward-kill-word

Kill text backwards by n words.

backward-paragraph

Move cursor backwards n paragraphs. Paragraphs are delimited by <NL><NL> or <NL><TAB> or <NL><SPACE>.

backward-word

Move cursor backwards by the specified number of words.

beginning-of-buffer

Move cursor to the top of the buffer. If set, keep mark's position, otherwise set at current position. A numeric argument n will move n/10th of the way from the top.

beginning-of-line

Move cursor to the beginning of the line.

blink-and-insert

Self-insert a character, then search backwards and blink its matching delimiter. For delimiters other than parenthesis, brackets, and braces, the character itself is used as its own match. Can be used in the startup file with the global-set-key command.

bsmap-mode

Toggle bsmap mode, where DEL and C-h are swapped.

c-mode

Toggle a KNF-compliant mode for editing C program files.

call-last-kbd-macro

Invoke the keyboard macro.

capitalize-word

Capitalize n words; i.e. convert the first character of the word to upper case, and subsequent letters to lower case.

cd

Change the global working directory. See also global-wd-mode.

column-number-mode

Toggle whether the column number is displayed in the modeline.

copy-region-as-kill

Copy all of the characters in the region to the kill buffer, clearing the mark afterwards. This is a bit like a kill-region followed by a yank.

count-matches

Count the number of lines matching the supplied regular expression.

count-non-matches

Count the number of lines not matching the supplied regular expression.

cscope-find-this-symbol

List the matches for the given symbol.

cscope-find-global-definition

List global definitions for the given literal.

cscope-find-called-functions

List functions called from the given function.

cscope-find-functions-calling-this-function

List functions calling the given function.

cscope-find-this-text-string

List locations matching the given text string.

cscope-find-egrep-pattern

List locations matching the given extended regular expression pattern.

cscope-find-this-file

List filenames matching the given filename.

cscope-find-files-including-file

List files that #include the given filename.

cscope-next-symbol

Navigate to the next match.

cscope-prev-symbol

Navigate to the previous match.

cscope-next-file

Navigate to the next file.

cscope-prev-file

Navigate to the previous file.

cscope-create-list-of-files-to-index

Create cscope's List and Index in the given directory.

define-key

Prompts the user for a named keymap (mode), a key, and an mg command, then creates a keybinding in the appropriate map.

delete-backward-char

Delete backwards n characters. Like delete-char, this actually does a kill if presented with an argument.

delete-blank-lines

Delete blank lines around dot. If dot is sitting on a blank line, this command deletes all the blank lines above and below the current line. Otherwise, it deletes all of the blank lines after the current line.

delete-char

Delete n characters forward. If any argument is present, it kills rather than deletes, saving the result in the kill buffer.

delete-horizontal-space

Delete any whitespace around the dot.

delete-leading-space

Delete leading whitespace on the current line.

delete-trailing-space

Delete trailing whitespace on the current line.

delete-matching-lines

Delete all lines after dot that contain a string matching the supplied regular expression.

delete-non-matching-lines

Delete all lines after dot that don't contain a string matching the supplied regular expression.

delete-other-windows

Make the current window the only window visible on the screen.

delete-window

Delete current window.

describe-bindings

List all global and local keybindings, putting the result in the *help* buffer.

describe-key-briefly

Read a key from the keyboard, and look it up in the keymap. Display the name of the function currently bound to the key.

diff-buffer-with-file

View the differences between buffer and its associated file.

digit-argument

Process a numerical argument for keyboard-invoked functions.

dired-jump

Open a dired buffer containing the current buffer's directory location.

downcase-region

Set all characters in the region to lower case.

downcase-word

Set characters to lower case, starting at the dot, and ending n words away.

emacs-version

Return an mg version string.

end-kbd-macro

Stop defining a keyboard macro.

end-of-buffer

Move cursor to the end of the buffer. If set, keep mark's position, otherwise set at current position. A numeric argument n will move n/10th of the way from the end.

end-of-line

Move cursor to the end of the line.

enlarge-window

Enlarge the current window by shrinking either the window above or below it.

eval-current-buffer

Evaluate the current buffer as a series of mg commands. Useful for testing mg startup files.

eval-expression

Get one line from the user, and run it. Useful for testing expressions in mg startup files.

exchange-point-and-mark

Swap the values of "dot" and "mark" in the current window. Return an error if no mark is set.

execute-extended-command

Invoke an extended command; i.e. M-x. Call the message line routine to read in the command name and apply autocompletion to it. When it comes back, look the name up in the symbol table and run the command if it is found, passing arguments as necessary. Print an error if there is anything wrong.

fill-paragraph

Justify a paragraph, wrapping text at the current fill column.

find-file

Select a file for editing. First check if the file can be found in another buffer; if it is there, just switch to that buffer. If the file cannot be found, create a new buffer, read in the file from disk, and switch to the new buffer.

find-file-read-only

Same as find-file, except the new buffer is set to read-only.

find-alternate-file

Replace the current file with an alternate one. Semantics for finding the replacement file are the same as find-file, except the current buffer is killed before the switch. If the kill fails, or is aborted, revert to the original file.

find-file-other-window

Opens the specified file in a second buffer. Splits the current window if necessary.

find-tag

Jump to definition of tag at dot.

forward-char

Move cursor forwards (or backwards, if n is negative) n characters. Returns an error if the end of buffer is reached.

forward-paragraph

Move forward n paragraphs. Paragraphs are delimited by <NL><NL> or <NL><TAB> or <NL><SPACE>.

forward-word

Move the cursor forward by the specified number of words.

global-set-key

Bind a key in the global (fundamental) key map.

global-unset-key

Unbind a key from the global (fundamental) key map; i.e. set it to 'rescan'.

global-wd-mode

Toggle global working-directory mode. When enabled, mg defaults to opening files (and executing commands like compile and grep) relative to the global working directory. When disabled, a working directory is set for each buffer.

goto-line

Go to a specific line. If an argument is present, then it is the line number, else prompt for a line number to use.

help-help

Prompts for one of (a)propos, (b)indings, des(c)ribe key briefly.

insert

Insert a string, mainly for use from macros.

insert-buffer

Insert the contents of another buffer at dot.

insert-file

Insert a file into the current buffer at dot.

insert-with-wrap

Insert the bound character with word wrap. Check to see if we're past the fill column, and if so, justify this line.

isearch-backward

Use incremental searching, initially in the reverse direction. isearch ignores any explicit arguments. If invoked during macro definition or evaluation, the non-incremental search-backward is invoked instead.

isearch-forward

Use incremental searching, initially in the forward direction. isearch ignores any explicit arguments. If invoked during macro definition or evaluation, the non-incremental search-forward is invoked instead.

join-line

Join the current line to the previous. If called with an argument, join the next line to the current one.

just-one-space

Delete any whitespace around dot, then insert a space.

keyboard-quit

Abort the current action.

kill-buffer

Dispose of a buffer, by name. If the buffer name does not start and end with an asterisk, prompt the user if the buffer has been changed.

kill-line

Kill line. If called without an argument, it kills from dot to the end of the line, unless it is at the end of the line, when it kills the newline. If called with an argument of 0, it kills from the start of the line to dot. If called with a positive argument, it kills from dot forward over that number of newlines. If called with a negative argument it kills any text before dot on the current line, then it kills back abs(n) lines.

kill-paragraph

Delete n paragraphs starting with the current one.

kill-region

Kill the currently defined region.

kill-word

Delete forward n words.

leave-tmpdir-backups

Modifies the behaviour of backup-to-home-directory. Backup files that would normally reside in /tmp are left there and not moved to the ~/.mg.d directory.

line-number-mode

Toggle whether the line number is displayed in the modeline.

list-buffers

Display the list of available buffers. The first column in the output indicates which buffer is active with a '>' character. The second column indicates which buffers are modified. The third column indicates which buffers are read-only. The remaining columns are self-explanatory.

load

Prompt the user for a filename, and then execute commands from that file.

local-set-key

Bind a key mapping in the local (topmost) mode.

local-unset-key

Unbind a key mapping in the local (topmost) mode.

make-backup-files

Toggle generation of backup files. Enabled by default.

make-directory

Prompt the user for a path or directory name which is then created.

mark-paragraph

Mark n paragraphs.

mark-whole-buffer

Marks whole buffer as a region by putting dot at the beginning and mark at the end of buffer.

meta-key-mode

When disabled, the meta key can be used to insert extended-ascii (8-bit) characters. When enabled, the meta key acts as usual.

negative-argument

Process a negative argument for keyboard-invoked functions.

newline

Insert a newline into the current buffer.

newline-and-indent

Insert a newline, then enough tabs and spaces to duplicate the indentation of the previous line, respecting no-tab-mode and the buffer tab width.

next-line

Move forward n lines.

no-tab-mode

Toggle notab mode. In this mode, spaces are inserted rather than tabs. Can be set globally with set-default-mode.

not-modified

Turn off the modified flag in the current buffer.

open-line

Open up some blank space. Essentially, insert n newlines, then back up over them.

other-window

The command to make the next (down the screen) window the current window. There are no real errors, although the command does nothing if there is only 1 window on the screen.

overwrite-mode

Toggle overwrite mode in the current buffer, where typing overwrites existing characters rather than inserting them. Can be set globally with set-default-mode.

prefix-region

Inserts a prefix string before each line of a region. The prefix string is settable by using set-prefix-string or by invoking this command with a prefix argument.

previous-line

Move backwards n lines.

previous-window

This command makes the previous (up the screen) window the current window. There are no errors, although the command does not do a lot if there is only 1 window.

pop-tag-mark

Return to position where find-tag was previously invoked.

push-shell

Suspend mg and switch to alternate screen, if available.

pwd

Display current (global) working directory in the status area.

query-replace

Query Replace. Search and replace strings selectively, prompting after each match.

replace-regexp

Replace regular expression globally without individual prompting.

replace-string

Replace string globally without individual prompting.

query-replace-regexp

Replace strings selectively. Does a search and replace operation using regular expressions for both patterns.

quoted-insert

Insert the next character verbatim into the current buffer; i.e. ignore any function bound to that key.

re-search-again

Perform a regular expression search again, using the same search string and direction as the last search command.

re-search-backward

Search backwards using a regular expression. Get a search string from the user, and search, starting at dot and proceeding toward the front of the buffer. If found, dot is left pointing at the first character of the pattern [the last character that was matched].

re-search-forward

Search forward using a regular expression. Get a search string from the user and search for it starting at dot. If found, move dot to just after the matched characters. display does all the hard stuff. If not found, it just prints a message.

recenter

Reposition dot in the current window. By default, the dot is centered. If given a positive argument (n), the display is repositioned to line n. If n is negative, it is that line from the bottom.

redraw-display

Refresh the display. Recomputes all window sizes in case something has changed.

revert-buffer

Revert the current buffer to the latest file on disk.

save-buffer

Save the contents of the current buffer if it has been changed, optionally creating a backup copy.

save-buffers-kill-emacs

Offer to save modified buffers and quit mg.

save-some-buffers

Look through the list of buffers, offering to save any buffer that has been changed. Buffers that are not associated with files (such as *scratch*, *grep*, *compile*) are ignored.

scroll-down

Scroll backwards n pages. A two-line overlap between pages is assumed. If given a repeat argument, scrolls back lines, not pages.

scroll-one-line-down

Scroll the display down n lines without changing the cursor position.

scroll-one-line-up

Scroll the display n lines up without moving the cursor position.

scroll-other-window

Scroll the next window in the window list window forward n pages.

scroll-up

Scroll forward one page. A two-line overlap between pages is assumed. If given a repeat argument, scrolls back lines, not pages.

search-again

Search again, using the same search string and direction as the last search command.

search-backward

Reverse search. Get a search string from the user, and search, starting at dot and proceeding toward the front of the buffer. If found, dot is left pointing at the first character of the pattern (the last character that was matched).

search-forward

Search forward. Get a search string from the user, and search for it starting at dot. If found, dot gets moved to just after the matched characters, if not found, print a message.

self-insert-command

Insert a character.

sentence-end-double-space

Toggle double or single spaces for end of sentences. Double is the default. Currently only affects fill-paragraph.

set-case-fold-search

Set case-fold searching, causing case not to matter in regular expression searches. This is the default.

set-case-replace

Preserve the case of the replaced string. This is the default.

set-default-mode

Append the supplied mode to the list of default modes used by subsequent buffer creation. Built in modes include: fill, indent, notab and overwrite.

set-fill-column

Prompt the user for a fill column. Used by auto-fill-mode.

set-mark-command

Sets the mark in the current window to the current dot location.

set-prefix-string

Sets the prefix string to be used by the prefix-region command.

set-tab-width

Set the tab width for the current buffer, or the default for new buffers if called with a prefix argument or from the startup file.

shell-command

Execute external command from mini-buffer. With an universal argument it inserts the command output into the current buffer.

shell-command-on-region

Provide the text in region to the shell command as input. With an universal argument it replaces the region with the command output.

shrink-window

Shrink current window by one line. The window immediately below is expanded to pick up the slack. If only one window is present, this command has no effect.

space-to-tabstop

Insert enough spaces to reach the next tab-stop position. By default, tab-stops occur every 8 characters.

split-window-vertically

Split the current window. A window smaller than 3 lines cannot be split.

start-kbd-macro

Start defining a keyboard macro. Macro definition is ended by invoking end-kbd-macro.

suspend-emacs

Suspend mg and switch back to alternate screen, if in use.

switch-to-buffer

Prompt and switch to a new buffer in the current window.

switch-to-buffer-other-window

Switch to buffer in another window.

toggle-read-only

Toggle the read-only flag on the current buffer.

toggle-read-only-all

Toggle the read-only flag on all non-ephemeral buffers. A simple toggle that switches a global read-only flag either on or off.

transpose-chars

Transpose the two characters in front of and under dot, then move forward one character. Treat newline characters the same as any other.

transpose-paragraphs

Transpose adjacent paragraphs. If multiple iterations are requested, the current paragraph will be moved n paragraphs forward.

transpose-words

Transpose adjacent words.

undo

Undo the most recent action. If invoked again without an intervening command, move the undo pointer to the previous action and undo it.

undo-boundary

Add an undo boundary. This is not usually done interactively.

undo-boundary-toggle

Toggle whether undo boundaries are generated. Undo boundaries are often disabled before operations that should be considered atomically undoable.

undo-enable

Toggle whether undo information is kept.

undo-list

Show the undo records for the current buffer in a new buffer.

universal-argument

Repeat the next command 4 times. Usually bound to C-u. This command may be stacked; e.g. C-u C-u C-f moves the cursor forward 16 characters.

upcase-region

Upper case region. Change all of the lower case characters in the region to upper case.

upcase-word

Move the cursor forward by the specified number of words. As it moves, convert any characters to upper case.

visible-bell

Toggle the visible bell. If this toggle is on, the modeline will flash.

visit-tags-table

Load tags file to be used for subsequent find-tag.

what-cursor-position

Display a bunch of useful information about the current location of dot. The character under the cursor (in octal), the current line, row, and column, and approximate position of the cursor in the file (as a percentage) is displayed. The column position assumes an infinite position display; it does not truncate just because the screen does.

write-file

Ask for a file name and write the contents of the current buffer to that file. Update the remembered file name and clear the buffer changed flag.

yank

Yank text from kill-buffer. Unlike emacs, the mg kill buffer consists only of the most recent kill. It is not a ring.

zap-to-char

Ask for a character and delete text from the current cursor position until the next instance of that character, including it.

zap-up-to-char

Like zap-to-char but doesn't delete the target character.

Specific key bindings are available in dired mode.

The following are a list of the commands specific to dired mode:

dired-create-directory

Create a directory.

dired-do-copy

Copy the file listed on the current line of the dired buffer.

dired-do-flagged-delete

Delete the files that have been flagged for deletion.

dired-do-rename

Rename the file listed on the current line of the dired buffer.

dired-find-alternate-file

Replace the current dired buffer with an alternate one as specified by the position of the cursor in the dired buffer.

dired-find-file

Open the file on the current line of the dired buffer. If the cursor is on a directory, it will be opened in dired mode.

dired-flag-file-deletion

Flag the file listed on the current line for deletion. This is indicated in the buffer by putting a D at the left margin. No files are actually deleted until the function dired-do-flagged-delete is executed.

dired-find-file-other-window

Open the file on the current line of the dired buffer in a different window.

dired-goto-file

Move the cursor to a file name in the dired buffer.

dired-next-line

Move the cursor to the next line.

dired-other-window

This function works just like dired, except that it puts the dired buffer in another window.

dired-previous-line

Move the cursor to the previous line.

dired-revert

Refresh the dired buffer while retaining any flags.

dired-scroll-down

Scroll down the dired buffer.

dired-scroll-up

Scroll up the dired buffer.

dired-shell-command

Pipe the file under the current cursor position through a shell command.

dired-unmark

Remove the deletion flag for the file on the current line.

dired-unmark-backward

Remove the deletion flag from the file listed on the previous line of the dired buffer, then move up to that line.

dired-up-directory

Open a dired buffer in the parent directory.

quit-window

Close the current dired buffer.

There are two configuration files, .mg and .mg-TERM. Here, TERM represents the name of the terminal type; e.g. if the terminal type is set to “vt100”, mg will use .mg-vt100 as a startup file. The terminal type startup file is used first.

The startup file format is a list of commands, one per line, as used for interactive evaluation. Strings that are normally entered by the user at any subsequent prompts may be specified after the command name; e.g.:

global-set-key ")" self-insert-command
global-set-key "\^x\^f" find-file
global-set-key "\e[Z" backward-char
set-default-mode fill
set-fill-column 72
auto-execute *.c c-mode

Comments can be added to the startup files by placing ‘;’ or ‘#’ as the first character of a line.

~/.mg

normal startup file

~/.mg-TERM

terminal-specific startup file

~/.mg.d

alternative backup file location

/usr/share/doc/mg/tutorial

concise tutorial

ctags(1), vi(1)

Since it is written completely in C, there is currently no language in which extensions can be written; however, keys can be rebound and certain parameters can be changed in startup files.

In order to use 8-bit characters (such as German umlauts), the Meta key needs to be disabled via the meta-key-mode command.

Multi-byte character sets, such as UTF-8, are not supported.

editline(7), oksh(1).