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GNU Info File
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1995-09-11
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1,112 lines
This is Info file ../info/emacs, produced by Makeinfo-1.55 from the
input file emacs.texi.
File: emacs, Node: Shell Mode, Next: Shell History, Prev: Interactive Shell, Up: Shell
Shell Mode
----------
Shell buffer use Shell mode, which defines several special keys
attached to the `C-c' prefix. They are chosen to resemble the usual
editing and job control characters present in shells that are not under
Emacs, except that you must type `C-c' first. Here is a complete list
of the special key bindings of Shell mode:
`RET'
At end of buffer send line as input; otherwise, copy current line
to end of buffer and send it (`comint-send-input'). When a line is
copied, any text at the beginning of the line that matches the
variable `shell-prompt-pattern' is left out; this variable's value
should be a regexp string that matches the prompts that your shell
uses.
`TAB'
Complete the command name or file name before point in the shell
buffer (`comint-dynamic-complete'). TAB also completes history
references (*note History References::.) and environment variable
names.
The variable `shell-completion-fignore' specifies a list of file
name extensions to ignore in Shell mode completion. The default
setting ignores file names ending in `~', `#' or `%'. Other
related Comint modes use the variable `comint-completion-fignore'
instead.
`M-?'
Display temporarily a list of the possible completions of the file
name before point in the shell buffer
(`comint-dynamic-list-filename-completions').
`C-d'
Either delete a character or send EOF
(`comint-delchar-or-maybe-eof'). Typed at the end of the shell
buffer, `C-d' sends EOF to the subshell. Typed at any other
position in the buffer, `C-d' deletes a character as usual.
`C-c C-a'
Move to the beginning of the line, but after the prompt if any
(`comint-bol').
`C-c C-u'
Kill all text pending at end of buffer to be sent as input
(`comint-kill-input').
`C-c C-w'
Kill a word before point (`backward-kill-word').
`C-c C-c'
Interrupt the shell or its current subjob if any
(`comint-interrupt-subjob').
`C-c C-z'
Stop the shell or its current subjob if any (`comint-stop-subjob').
`C-c C-\'
Send quit signal to the shell or its current subjob if any
(`comint-quit-subjob').
`C-c C-o'
Kill the last batch of output from a shell command
(`comint-kill-output'). This is useful if a shell command spews
out lots of output that just gets in the way.
`C-c C-r'
`C-M-l'
Scroll to display the beginning of the last batch of output at the
top of the window; also move the cursor there
(`comint-show-output').
`C-c C-e'
Scroll to put the end of the buffer at the bottom of the window
(`comint-show-maximum-output').
`C-c C-f'
Move forward across one shell command, but not beyond the current
line (`shell-forward-command'). The variable
`shell-command-regexp' specifies how to recognize the end of a
command.
`C-c C-b'
Move backward across one shell command, but not beyond the current
line (`shell-backward-command').
`C-c C-l'
Display the buffer's history of shell commands in another window
(`comint-dynamic-list-input-ring').
`M-x dirs'
Ask the shell what its current directory is, so that Emacs can
agree with the shell.
`M-x send-invisible RET TEXT RET'
Send TEXT as input to the shell, after reading it without echoing.
This is useful when a shell command runs a program that asks for
a password.
Alternatively, you can arrange for Emacs to notice password prompts
and turn off echoing for them, as follows:
(add-hook `comint-output-filter-functions
`comint-watch-for-password-prompt)
`M-x comint-continue-subjob'
Continue the shell process. This is useful if you accidentally
suspend the shell process.(1)
`M-x comint-strip-ctrl-m'
Discard all control-m characters from the shell output. The most
convenient way to use this command is to make it run automatically
when you get output from the subshell. To do that, evaluate this
Lisp expression:
(add-hook 'comint-output-filter-functions
'comint-strip-ctrl-m)
`M-x comint-truncate-buffer'
This command truncates the shell buffer to a certain maximum
number of lines, specified by the variable
`comint-buffer-maximum-size'. Here's how to do this automatically
each time you get output from the subshell:
(add-hook 'comint-output-filter-functions
'comint-truncate-buffer)
Shell mode also customizes the paragraph commands so that only shell
prompts start new paragraphs. Thus, a paragraph consists of an input
command plus the output that follows it in the buffer.
Shell mode is a derivative of Comint mode, a general purpose mode for
communicating with interactive subprocesses. Most of the features of
Shell mode actually come from Comint mode, as you can see from the
command names listed above. The specialization of Shell mode in
particular include the choice of regular expression for detecting
prompts, the directory tracking feature, and a few user commands.
Other Emacs features that use variants of Comint mode include GUD
(*note Debuggers::.) and `M-x run-lisp' (*note External Lisp::.).
You can use `M-x comint-run' to execute any program of your choice
in a subprocess using unmodified Comint mode--without the
specializations of Shell mode.
---------- Footnotes ----------
(1) You should not suspend the shell process. Suspending a subjob
of the shell is a completely different matter--that is normal practice,
but you must use the shell to continue the subjob; this command won't
do it.
File: emacs, Node: Shell History, Next: Shell Options, Prev: Shell Mode, Up: Shell
Shell Command History
---------------------
Shell buffers support three ways of repeating earlier commands. You
can use the same keys used in the minibuffer; these work much as they do
in the minibuffer, inserting text from prior commands while point
remains always at the end of the buffer. You can move through the
buffer to previous inputs in their original place, then resubmit them or
copy them to the end. Or you can use a `!'-style history reference.
* Menu:
* Ring: Shell Ring. Fetching commands from the history list.
* Copy: Shell History Copying. Moving to a command and then copying it.
* History References:: Expanding `!'-style history references.
File: emacs, Node: Shell Ring, Next: Shell History Copying, Up: Shell History
Shell History Ring
..................
`M-p'
Fetch the next earlier old shell command.
`M-n'
Fetch the next later old shell command.
`M-r REGEXP RET'
`M-s REGEXP RET'
Search backwards or forwards for old shell commands that match
REGEXP.
Shell buffers provide a history of previously entered shell
commands. To reuse shell commands from the history, use the editing
commands `M-p', `M-n', `M-r' and `M-s'. These work just like the
minibuffer history commands except that they operate on the text at the
end of the shell buffer, where you would normally insert text to send
to the shell.
`M-p' fetches an earlier shell command to the end of the shell
buffer. Successive use of `M-p' fetches successively earlier shell
commands, each replacing any text that was already present as potential
shell input. `M-n' does likewise except that it finds successively
more recent shell commands from the buffer.
The history search commands `M-r' and `M-s' read a regular
expression and search through the history for a matching command. Aside
from the choice of which command to fetch, they work just like `M-p'
and `M-r'. If you enter an empty regexp, these commands reuse the same
regexp used last time.
When you find the previous input you want, you can resubmit it by
typing RET, or you can edit it first and then resubmit it if you wish.
These commands get the text of previous shell commands from a special
history list, not from the shell buffer itself. Thus, editing the shell
buffer, or even killing large parts of it, does not affect the history
that these commands access.
Some shells store their command histories in files so that you can
refer to previous commands from previous shell sessions. Emacs reads
the command history file for your chosen shell, to initialize its own
command history. The file name is `~/.bash_history' for bash,
`~/.sh_history' for ksh, and `~/.history' for other shells.
File: emacs, Node: Shell History Copying, Next: History References, Prev: Shell Ring, Up: Shell History
Shell History Copying
.....................
`C-c C-p'
Move point to the previous prompt (`comint-previous-prompt').
`C-c C-n'
Move point to the following prompt (`comint-next-prompt').
`C-c RET'
Copy the input command which point is in, inserting the copy at
the end of the buffer (`comint-copy-old-input'). This is useful
if you move point back to a previous command. After you copy the
command, you can submit the copy as input with RET. If you wish,
you can edit the copy before resubmitting it.
Moving to a previous input and then copying it with `C-c RET'
produces the same results--the same buffer contents--that you would get
by using `M-p' enough times to fetch that previous input from the
history list. However, `C-c RET' copies the text from the buffer,
which can be different from what is in the history list if you edit the
input text in the buffer after it has been sent.
File: emacs, Node: History References, Prev: Shell History Copying, Up: Shell History
Shell History References
........................
Various shells including csh and bash support "history references"
that begin with `!' and `^'. Shell mode can understands these
constructs and perform the history substitution for you. If you insert
a history reference and type TAB, this searches the input history for a
matching command, performs substitution if necessary, and places the
result in the buffer in place of the history reference. For example,
you can fetch the most recent command beginning with `mv' with `! m v
TAB'. You can edit the command if you wish, and then resubmit the
command to the shell by typing RET.
History references take effect only following a shell prompt. The
variable `shell-prompt-pattern' specifies how to recognize a shell
prompt. Comint modes in general use the variable
`comint-prompt-regexp' to specify how to find a prompt; Shell mode uses
`shell-prompt-pattern' to set up the local value of
`comint-prompt-regexp'.
Shell mode can optionally expand history references in the buffer
when you send them to the shell. To request this, set the variable
`comint-input-autoexpand' to `input'.
You can make SPC perform history expansion by binding SPC to the
command `comint-magic-space'.
File: emacs, Node: Shell Options, Next: Remote Host, Prev: Shell History, Up: Shell
Shell Mode Options
------------------
If the variable `comint-scroll-to-bottom-on-input' is non-`nil',
insertion and yank commands scroll the selected window to the bottom
before inserting.
If `comint-scroll-show-maximum-output' is non-`nil' (which is the
default), then scrolling due to arrival of output tries to place the
last line of text at the bottom line of the window, so as to show as
much useful text as possible. (This mimics the scrolling behavior of
many terminals.)
By setting `comint-scroll-to-bottom-on-output', you can opt for
having point jump to the end of the buffer whenever output arrives--no
matter where in the buffer point was before. If the value is `this',
point jumps in the selected window. If the value is `all', point jumps
in each window that shows the comint buffer. If the value is `other',
point jumps in all nonselected windows that show the current buffer.
The default value is `nil', which means point does not jump to the end.
The variable `comint-input-ignoredups' controls whether successive
identical inputs are stored in the input history. A non-`nil' value
means to omit an input that is the same as the previous input. The
default is `nil', which means to store each input even if it is equal
to the previous input.
Three variables customize file name completion. The variable
`comint-completion-addsuffix' controls whether completion inserts a
space or a slash to indicate a fully completed file or directory name
(non-`nil' means do insert a space or slash).
`comint-completion-recexact', if non-`nil', directs TAB to choose the
shortest possible completion if the usual Emacs completion algorithm
cannot add even a single character. `comint-completion-autolist', if
non-`nil', says to list all the possible completions whenever
completion is not exact.
The command `comint-dynamic-complete-variable' does variable name
completion using the environment variables as set within Emacs. The
variables controlling file name completion apply to variable name
completion too. This command is normally available through the menu
bar.
Command completion normally considers only executable files. If you
set `shell-command-execonly' to `nil', it considers nonexecutable files
as well.
You can configure the behavior of `pushd'. Variables control
whether `pushd' behaves like `cd' if no argument is given
(`shell-pushd-tohome'), pop rather than rotate with a numeric argument
(`shell-pushd-dextract'), and only add directories to the directory
stack if they are not already on it (`shell-pushd-dunique'). The
values you choose should match the underlying shell, of course.
File: emacs, Node: Remote Host, Prev: Shell Options, Up: Shell
Remote Host Shell
-----------------
Emacs provides two commands for logging in to another computer and
communicating with it through an Emacs buffer.
`M-x telnet RET HOSTNAME RET'
Set up a Telnet connection to the computer named HOSTNAME.
`M-x rlogin RET HOSTNAME RET'
Set up an Rlogin connection to the computer named HOSTNAME.
Use `M-x telnet' to set up a Telnet connection to another computer.
(Telnet is the standard Internet protocol for remote login.) It reads
the host name of the other computer as an argument with the minibuffer.
Once the connection is established, talking to the other computer
works like talking to a subshell: you can edit input with the usual
Emacs commands, and send it a line at a time by typing RET. The output
is inserted in the Telnet buffer interspersed with the input.
Use `M-x rlogin' to set up an Rlogin connection. Rlogin is another
remote login communication protocol, essentially much like the Telnet
protocol but incompatible with it, and supported only by certain
systems. Rlogin's advantages are that you can arrange not to have to
give your user name and password when communicating between two machines
you frequently use, and that you can make an 8-bit-clean connection.
(To do that in Emacs, set `rlogin-explicit-args' to `("-8")' before you
run Rlogin.)
`M-x rlogin' sets up the default file directory of the Emacs buffer
to access the remote host via FTP (*note File Names::.), and it tracks
the shell commands that change the current directory just like Shell
mode.
File: emacs, Node: Emacs Server, Next: Hardcopy, Prev: Shell, Up: Top
Using Emacs as a Server
=======================
Various programs such as `mail' can invoke your choice of editor to
edit a particular piece of text, such as a message that you are
sending. By convention, most of these programs use the environment
variable `EDITOR' to specify which editor to run. If you set `EDITOR'
to `emacs', they invoke Emacs--but in an inconvenient fashion, by
starting a new, separate Emacs process. This is inconvenient because
it takes time and because the new Emacs process doesn't share the
buffers in the existing Emacs process.
You can arrange to use your existing Emacs process as the editor for
programs like `mail' by using the Emacs client and Emacs server
programs. Here is how.
First, the preparation. Within Emacs, call the function
`server-start'. (Your `.emacs' file can do this automatically if you
add the expression `(server-start)' to it.) Then, outside Emacs, set
the `EDITOR' environment variable to `emacsclient'. (Note that some
programs use a different environment variable; for example, to make TeX
use `emacsclient', you should set the `TEXEDIT' environment variable to
`emacsclient +%d %s'.)
Then, whenever any program invokes your specified `EDITOR' program,
the effect is to send a message to your principal Emacs telling it to
visit a file. (That's what the program `emacsclient' does.) Emacs
displays the buffer immediately and you can immediately begin editing
it.
When you've finished editing that buffer, type `C-x #'
(`server-edit'). This saves the file and sends a message back to the
`emacsclient' program telling it to exit. The programs that use
`EDITOR' wait for the "editor" (actually, `emacsclient') to exit. `C-x
#' also checks for other pending external requests to edit various
files, and selects the next such file.
You can switch to a server buffer manually if you wish; you don't
have to arrive at it with `C-x #'. But `C-x #' is the only way to say
that you are "finished" with one.
If you set the variable `server-window' to a window or a frame, `C-x
#' displays the server buffer in that window or in that frame.
While `mail' or another application is waiting for `emacsclient' to
finish, `emacsclient' does not read terminal input. So the terminal
that `mail' was using is effectively blocked for the duration. In
order to edit with your principal Emacs, you need to be able to use it
without using that terminal. There are two ways to do this:
* Using a window system, run `mail' and the principal Emacs in two
separate windows. While `mail' is waiting for `emacsclient', the
window where it was running is blocked, but you can use Emacs by
switching windows.
* Use Shell mode in Emacs to run the other program such as `mail';
then, `emacsclient' blocks only the subshell under Emacs, and you
can still use Emacs to edit the file.
Some programs write temporary files for you to edit. After you edit
the temporary file, the program reads it back and deletes it. If the
Emacs server is later asked to edit the same file name, it should assume
this has nothing to do with the previous occasion for that file name.
The server accomplishes this by killing the temporary file's buffer when
you finish with the file. Use the variable `server-temp-file-regexp'
to specify which files are temporary in this sense; its value should be
a regular expression that matches file names that are temporary.
File: emacs, Node: Hardcopy, Next: Postscript, Prev: Emacs Server, Up: Top
Hardcopy Output
===============
The Emacs commands for making hardcopy let you print either an entire
buffer or just part of one, either with or without page headers. See
also the hardcopy commands of Dired (*note Misc File Ops::.) and the
diary (*note Diary Commands::.).
`M-x print-buffer'
Print hardcopy of current buffer with page headings containing the
file name and page number.
`M-x lpr-buffer'
Print hardcopy of current buffer without page headings. makes no
page headings.
`M-x print-region'
Like `print-buffer' but print only the current region.
`M-x lpr-region'
Like `lpr-buffer' but print only the current region.
The hardcopy commands (aside from the Postscript commands) pass extra
switches to the `lpr' program based on the value of the variable
`lpr-switches'. Its value should be a list of strings, each string an
option starting with `-'. For example, to use a printer named
`nearme', set `lpr-switches' like this:
(setq lpr-switches '("-Pnearme"))
The variable `lpr-header-switches' similarly specifies the extra
switches to use to make page headers.
File: emacs, Node: Postscript, Next: Sorting, Prev: Hardcopy, Up: Top
Postscript Hardcopy
===================
These commands convert buffer contents to Postscript, either
printing it or leaving it in another Emacs buffer.
`M-x ps-print-buffer'
Print hardcopy of the current buffer in Postscript form.
`M-x ps-print-region'
Print hardcopy of the current region in Postscript form.
`M-x ps-print-buffer-with-faces'
Print hardcopy of the current buffer in Postscript form, showing
the faces used in the text by means of Postscript features.
`M-x ps-print-region-with-faces'
Print hardcopy of the current region in Postscript form, showing
the faces used in the text.
`M-x ps-spool-buffer'
Generate Postscript for the current buffer text.
`M-x ps-spool-region'
Generate Postscript for the current region.
`M-x ps-spool-buffer-with-faces'
Generate Postscript for the current buffer, showing the faces used.
`M-x ps-spool-region-with-faces'
Generate Postscript for the current region, showing the faces used.
The Postscript commands, `ps-print-buffer' and `ps-print-region',
print buffer contents in Postscript form. One command prints the
entire buffer; the other, just the region. The corresponding
`-with-faces' commands, `ps-print-buffer-with-faces' and
`ps-print-region-with-faces', use Postscript features to show the faces
(fonts and colors) in the text properties of the text being printed.
All four of the commands above use the variables `ps-lpr-command'
and `ps-lpr-switches' to specify how to print the output.
`ps-lpr-command' specifies the command name to run, and
`ps-lpr-switches' specifies command line options to use. If you don't
set these variables yourself, they take their initial values from
`lpr-command' and `lpr-switches'.
The variable `ps-print-header' controls whether these commands add
header lines to each page--set it to `nil' to turn headers off. You
can turn off color processing by setting `ps-print-color-p' to `nil'.
Many other customization variables for these commands are defined and
described in the Lisp file `ps-print.el'.
The commands whose names have `spool' instead of `print' generate
the Postscript output in an Emacs buffer instead of sending it to the
printer.
File: emacs, Node: Sorting, Next: Narrowing, Prev: Postscript, Up: Top
Sorting Text
============
Emacs provides several commands for sorting text in the buffer. All
operate on the contents of the region (the text between point and the
mark). They divide the text of the region into many "sort records",
identify a "sort key" for each record, and then reorder the records
into the order determined by the sort keys. The records are ordered so
that their keys are in alphabetical order, or, for numeric sorting, in
numeric order. In alphabetic sorting, all upper case letters `A'
through `Z' come before lower case `a', in accord with the ASCII
character sequence.
The various sort commands differ in how they divide the text into
sort records and in which part of each record is used as the sort key.
Most of the commands make each line a separate sort record, but some
commands use paragraphs or pages as sort records. Most of the sort
commands use each entire sort record as its own sort key, but some use
only a portion of the record as the sort key.
`M-x sort-lines'
Divide the region into lines, and sort by comparing the entire
text of a line. A numeric argument means sort into descending
order.
`M-x sort-paragraphs'
Divide the region into paragraphs, and sort by comparing the entire
text of a paragraph (except for leading blank lines). A numeric
argument means sort into descending order.
`M-x sort-pages'
Divide the region into pages, and sort by comparing the entire
text of a page (except for leading blank lines). A numeric
argument means sort into descending order.
`M-x sort-fields'
Divide the region into lines, and sort by comparing the contents of
one field in each line. Fields are defined as separated by
whitespace, so the first run of consecutive non-whitespace
characters in a line constitutes field 1, the second such run
constitutes field 2, etc.
Specify which field to sort by with a numeric argument: 1 to sort
by field 1, etc. A negative argument means count fields from the
right instead of from the left; thus, minus 1 means sort by the
last field. If several lines have identical contents in the field
being sorted, they keep same relative order that they had in the
original buffer.
A negative argument means count fields from the right (from the
end of the line).
`M-x sort-numeric-fields'
Like `M-x sort-fields' except the specified field is converted to
an integer for each line, and the numbers are compared. `10'
comes before `2' when considered as text, but after it when
considered as a number.
`M-x sort-columns'
Like `M-x sort-fields' except that the text within each line used
for comparison comes from a fixed range of columns. See below for
an explanation.
`M-x reverse-region'
Reverse the order of the lines in the region. This is useful for
sorting into descending order by fields or columns, since those
sort commands do not have a feature for doing that.
For example, if the buffer contains this:
On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
whether the file has changed on disk since it was last visited or
saved. If it has, you are asked to confirm that you want to change
the buffer.
applying `M-x sort-lines' to the entire buffer produces this:
On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
saved. If it has, you are asked to confirm that you want to change
the buffer.
whether the file has changed on disk since it was last visited or
where the upper case `O' sorts before all lower case letters. If you
use `C-u 2 M-x sort-fields' instead, you get this:
implemented, Emacs also checks the first time you modify a buffer
saved. If it has, you are asked to confirm that you want to change
the buffer.
On systems where clash detection (locking of files being edited) is
whether the file has changed on disk since it was last visited or
where the sort keys were `Emacs', `If', `buffer', `systems' and `the'.
`M-x sort-columns' requires more explanation. You specify the
columns by putting point at one of the columns and the mark at the other
column. Because this means you cannot put point or the mark at the
beginning of the first line to sort, this command uses an unusual
definition of `region': all of the line point is in is considered part
of the region, and so is all of the line the mark is in, as well as all
the lines in between.
For example, to sort a table by information found in columns 10 to
15, you could put the mark on column 10 in the first line of the table,
and point on column 15 in the last line of the table, and then run
`sort-columns'. Equivalently, you could run it with the mark on column
15 in the first line and point on column 10 in the last line.
This can be thought of as sorting the rectangle specified by point
and the mark, except that the text on each line to the left or right of
the rectangle moves along with the text inside the rectangle. *Note
Rectangles::.
Many of the sort commands ignore case differences when comparing, if
`sort-fold-case' is non-`nil'.
File: emacs, Node: Narrowing, Next: Two-Column, Prev: Sorting, Up: Top
Narrowing
=========
"Narrowing" means focusing in on some portion of the buffer, making
the rest temporarily inaccessible. The portion which you can still get
to is called the "accessible portion". Canceling the narrowing, which
makes the entire buffer once again accessible, is called "widening".
The amount of narrowing in effect in a buffer at any time is called the
buffer's "restriction".
Narrowing can make it easier to concentrate on a single subroutine or
paragraph by eliminating clutter. It can also be used to restrict the
range of operation of a replace command or repeating keyboard macro.
`C-x n n'
Narrow down to between point and mark (`narrow-to-region').
`C-x n w'
Widen to make the entire buffer accessible again (`widen').
`C-x n p'
Narrow down to the current page (`narrow-to-page').
When you have narrowed down to a part of the buffer, that part
appears to be all there is. You can't see the rest, you can't move
into it (motion commands won't go outside the accessible part), you
can't change it in any way. However, it is not gone, and if you save
the file all the inaccessible text will be saved. The word `Narrow'
appears in the mode line whenever narrowing is in effect.
The primary narrowing command is `C-x n n' (`narrow-to-region'). It
sets the current buffer's restrictions so that the text in the current
region remains accessible but all text before the region or after the
region is inaccessible. Point and mark do not change.
Alternatively, use `C-x n p' (`narrow-to-page') to narrow down to
the current page. *Note Pages::, for the definition of a page.
The way to cancel narrowing is to widen with `C-x n w' (`widen').
This makes all text in the buffer accessible again.
You can get information on what part of the buffer you are narrowed
down to using the `C-x =' command. *Note Position Info::.
Because narrowing can easily confuse users who do not understand it,
`narrow-to-region' is normally a disabled command. Attempting to use
this command asks for confirmation and gives you the option of enabling
it; if you enable the command, confirmation will no longer be required
for it. *Note Disabling::.
File: emacs, Node: Two-Column, Next: Editing Binary Files, Prev: Narrowing, Up: Top
Two-Column Editing
==================
Two-column mode lets you conveniently edit two side-by-side columns
of text. It uses two side-by-side windows, each showing its own buffer.
There are three ways to enter two-column mode:
`C-x 6 2'
Enter two-column mode with the current buffer on the left, and on
the right, a buffer whose name is based on the current buffer's
name (`tc-two-columns'). If the right-hand buffer doesn't already
exist, it starts out empty; the current buffer's contents are not
changed.
This command is appropriate when the current buffer contains just
one column and you want to add another column.
`C-x 6 s'
Split the current buffer, which contains two-column text, into two
buffers, and display them side by side (`tc-split'). The current
buffer becomes the left-hand buffer, but the text in the right-hand
column is moved into the right-hand buffer. The current column
specifies the split point. Splitting starts with the current line
and continues to the end of the buffer.
This command is appropriate when you have a buffer that already
contains two-column text, and you wish to separate the columns
temporarily.
`C-x 6 b BUFFER RET'
Enter two-column mode using the current buffer as the left-hand
buffer, and using buffer BUFFER as the right-hand buffer
(`tc-associate-buffer').
`C-x 6 s' looks for a column separator which is a string that
appears on each line between the two columns. You can specify the width
of the separator with a numeric argument to `C-x 6 s'; that many
characters, before point, constitute the separator string. By default,
the width is 1, so the column separator is the character before point.
When a line has the separator at the proper place, `C-x 6 s' puts
the text after the separator into the right-hand buffer, and deletes the
separator. Lines that don't have the column separator at the proper
place remain unsplit; they stay in the left-hand buffer, and the
right-hand buffer gets an empty line to correspond. (This is the way
to write a line that spans both columns while in two-column mode: write
it in the left-hand buffer, and put an empty line in the right-hand
buffer.)
It's not a good idea to use ordinary scrolling commands during
two-column editing, because that separates the two parts of each split
line. Instead, use these special scroll commands:
`C-x 6 SPC'
Scroll both buffers up, in lock step (`tc-scroll-up').
`C-x 6 DEL'
Scroll both buffers down, in lock step (`tc-scroll-down').
`C-x 6 C-l'
Recenter both buffers, in lock step (`tc-recenter').
When you have edited both buffers as you wish, merge them with `C-x
6 1' (`tc-merge'). This copies the text from the right-hand buffer as
a second column in the other buffer. To go back to two-column editing,
use `C-x 6 s'.
Use `C-x 6 d' to disassociate the two buffers, leaving each as it
stands (`tc-dissociate'). If the other buffer, the one not current
when you type `C-x 6 d', is empty, `C-x 6 d' kills it.
File: emacs, Node: Editing Binary Files, Next: Saving Emacs Sessions, Prev: Two-Column, Up: Top
Editing Binary Files
====================
There is a special major mode for editing binary files: Hexl mode.
To use it, use `M-x hexl-find-file' instead of `C-x C-f' to visit the
file. This command converts the file's contents to hexadecimal and
lets you edit the translation. When you save the file, it is converted
automatically back to binary.
You can also use `M-x hexl-mode' to translate an existing buffer
into hex. This is useful if you visit a file normally and then discover
it is a binary file.
Ordinary text characters overwrite in Hexl mode. This is to reduce
the risk of accidentally spoiling the alignment of data in the file.
There are special commands for insertion. Here is a list of the
commands of Hexl mode:
`C-M-d'
Insert a byte with a code typed in decimal.
`C-M-o'
Insert a byte with a code typed in octal.
`C-M-x'
Insert a byte with a code typed in hex.
`C-x ['
Move to the beginning of a 1k-byte "page".
`C-x ]'
Move to the end of a 1k-byte "page".
`M-g'
Move to an address specified in hex.
`M-j'
Move to an address specified in decimal.
`C-c C-c'
Leave Hexl mode, going back to the major mode this buffer had
before you invoked `hexl-mode'.
File: emacs, Node: Saving Emacs Sessions, Next: Recursive Edit, Prev: Editing Binary Files, Up: Top
Saving Emacs Sessions
=====================
You can use the Desktop library to save the state of Emacs from one
session to another. Saving the state means that Emacs starts up with
the same set of buffers, major modes, buffer positions, and so on that
the previous Emacs session had.
To use Desktop, you should first add these lines to your `.emacs'
file, preferably at or near the end:
(load "desktop")
(desktop-load-default)
(desktop-read)
Then, to enable state saving in a particular Emacs session, use the
command `M-x desktop-save'. Once you have done this, the state of this
Emacs session will be saved when you exit Emacs.
In order for Emacs to recover the state from a previous session, you
must start it with the same current directory as you used when you
started the previous session.
The variable `desktop-files-not-to-save' controls which files are
excluded from state saving. Its value is a regular expression that
matches the files to exclude. By default, remote (ftp-accessed) files
are excluded; this is because visiting them again in the subsequent
session would be slow. If you want to include these files in state
saving, set `desktop-files-not-to-save' to `"^$"'.
File: emacs, Node: Recursive Edit, Next: Emulation, Prev: Saving Emacs Sessions, Up: Top
Recursive Editing Levels
========================
A "recursive edit" is a situation in which you are using Emacs
commands to perform arbitrary editing while in the middle of another
Emacs command. For example, when you type `C-r' inside of a
`query-replace', you enter a recursive edit in which you can change the
current buffer. On exiting from the recursive edit, you go back to the
`query-replace'.
"Exiting" the recursive edit means returning to the unfinished
command, which continues execution. The command to exit is `C-M-c'
(`exit-recursive-edit').
You can also "abort" the recursive edit. This is like exiting, but
also quits the unfinished command immediately. Use the command `C-]'
(`abort-recursive-edit') to do this. *Note Quitting::.
The mode line shows you when you are in a recursive edit by
displaying square brackets around the parentheses that always surround
the major and minor mode names. Every window's mode line shows this,
in the same way, since being in a recursive edit is true of Emacs as a
whole rather than any particular window or buffer.
It is possible to be in recursive edits within recursive edits. For
example, after typing `C-r' in a `query-replace', you may type a
command that enters the debugger. This begins a recursive editing level
for the debugger, within the recursive editing level for `C-r'. Mode
lines display a pair of square brackets for each recursive editing
level currently in progress.
Exiting the inner recursive edit (such as, with the debugger `c'
command) resumes the command running in the next level up. When that
command finishes, you can then use `C-M-c' to exit another recursive
editing level, and so on. Exiting applies to the innermost level only.
Aborting also gets out of only one level of recursive edit; it returns
immediately to the command level of the previous recursive edit. If you
wish, you can then abort the next recursive editing level.
Alternatively, the command `M-x top-level' aborts all levels of
recursive edits, returning immediately to the top level command reader.
The text being edited inside the recursive edit need not be the same
text that you were editing at top level. It depends on what the
recursive edit is for. If the command that invokes the recursive edit
selects a different buffer first, that is the buffer you will edit
recursively. In any case, you can switch buffers within the recursive
edit in the normal manner (as long as the buffer-switching keys have
not been rebound). You could probably do all the rest of your editing
inside the recursive edit, visiting files and all. But this could have
surprising effects (such as stack overflow) from time to time. So
remember to exit or abort the recursive edit when you no longer need it.
In general, we try to minimize the use of recursive editing levels in
GNU Emacs. This is because they constrain you to "go back" in a
particular order-from the innermost level toward the top level. When
possible, we present different activities in separate buffers so that
you can switch between them as you please. Some commands switch to a
new major mode which provides a command to switch back. These
approaches give you more flexibility to go back to unfinished tasks in
the order you choose.
File: emacs, Node: Emulation, Next: Dissociated Press, Prev: Recursive Edit, Up: Top
Emulation
=========
GNU Emacs can be programmed to emulate (more or less) most other
editors. Standard facilities can emulate these:
EDT (DEC VMS editor)
Turn on EDT emulation with `M-x edt-emulation-on'. `M-x
edt-emulation-off' restores normal Emacs command bindings.
Most of the EDT emulation commands are keypad keys, and most
standard Emacs key bindings are still available. The EDT
emulation rebindings are done in the global keymap, so there is no
problem switching buffers or major modes while in EDT emulation.
vi (Berkeley editor)
Viper is the newest emulator for vi. It implements several levels
of emulation; level 1 is closest to vi itself, while level 5
departs somewhat from strict emulation to take advantage of the
capabilities of Emacs. To invoke Viper, type `M-x viper-mode'; it
will guide you the rest of the way and ask for the emulation level.
vi (another emulator)
`M-x vi-mode' enters a major mode that replaces the previously
established major mode. All of the vi commands that, in real vi,
enter "input" mode are programmed instead to return to the
previous major mode. Thus, ordinary Emacs serves as vi's "input"
mode.
Because vi emulation works through major modes, it does not work
to switch buffers during emulation. Return to normal Emacs first.
If you plan to use vi emulation much, you probably want to bind a
key to the `vi-mode' command.
vi (alternate emulator)
`M-x vip-mode' invokes another vi emulator, said to resemble real
vi more thoroughly than `M-x vi-mode'. "Input" mode in this
emulator is changed from ordinary Emacs so you can use ESC to go
back to emulated vi command mode. To get from emulated vi command
mode back to ordinary Emacs, type `C-z'.
This emulation does not work through major modes, and it is
possible to switch buffers in various ways within the emulator.
It is not so necessary to assign a key to the command `vip-mode' as
it is with `vi-mode' because terminating insert mode does not use
it.
For full information, see the long comment at the beginning of the
source file, which is `lisp/vip.el' in the Emacs distribution.
File: emacs, Node: Dissociated Press, Next: Amusements, Prev: Emulation, Up: Top
Dissociated Press
=================
`M-x dissociated-press' is a command for scrambling a file of text
either word by word or character by character. Starting from a buffer
of straight English, it produces extremely amusing output. The input
comes from the current Emacs buffer. Dissociated Press writes its
output in a buffer named `*Dissociation*', and redisplays that buffer
after every couple of lines (approximately) so you can read the output
as it comes out.
Dissociated Press asks every so often whether to continue generating
output. Answer `n' to stop it. You can also stop at any time by
typing `C-g'. The dissociation output remains in the `*Dissociation*'
buffer for you to copy elsewhere if you wish.
Dissociated Press operates by jumping at random from one point in the
buffer to another. In order to produce plausible output rather than
gibberish, it insists on a certain amount of overlap between the end of
one run of consecutive words or characters and the start of the next.
That is, if it has just printed out `president' and then decides to jump
to a different point in the file, it might spot the `ent' in `pentagon'
and continue from there, producing `presidentagon'.(1) Long sample
texts produce the best results.
A positive argument to `M-x dissociated-press' tells it to operate
character by character, and specifies the number of overlap characters.
A negative argument tells it to operate word by word and specifies the
number of overlap words. In this mode, whole words are treated as the
elements to be permuted, rather than characters. No argument is
equivalent to an argument of two. For your againformation, the output
goes only into the buffer `*Dissociation*'. The buffer you start with
is not changed.
Dissociated Press produces nearly the same results as a Markov chain
based on a frequency table constructed from the sample text. It is,
however, an independent, ignoriginal invention. Dissociated Press
techniquitously copies several consecutive characters from the sample
between random choices, whereas a Markov chain would choose randomly for
each word or character. This makes for more plausible sounding results,
and runs faster.
It is a mustatement that too much use of Dissociated Press can be a
developediment to your real work. Sometimes to the point of outragedy.
And keep dissociwords out of your documentation, if you want it to be
well userenced and properbose. Have fun. Your buggestions are welcome.
---------- Footnotes ----------
(1) This dissociword actually appeared during the Vietnam War, when
it was very appropriate.
File: emacs, Node: Amusements, Next: Customization, Prev: Dissociated Press, Up: Top
Other Amusements
================
If you are a little bit bored, you can try `M-x hanoi'. If you are
considerably bored, give it a numeric argument. If you are very very
bored, try an argument of 9. Sit back and watch.
If you want a little more personal involvement, try `M-x gomoku',
which plays the game Go Moku with you.
`M-x blackbox' and `M-x mpuz' are two kinds of puzzles. `blackbox'
challenges you to determine the location of objects inside a box by
tomography. `mpuz' displays a multiplication puzzle with letters
standing for digits in a code that you must guess--to guess a value,
type a letter and then the digit you think it stands for.
`M-x dunnet' runs an adventure-style exploration game, which is a
bigger sort of puzzle.
When you are frustrated, try the famous Eliza program. Just do `M-x
doctor'. End each input by typing `RET' twice.
When you are feeling strange, type `M-x yow'.
File: emacs, Node: Customization, Next: Quitting, Prev: Amusements, Up: Top
Customization
*************
This chapter talks about various topics relevant to adapting the
behavior of Emacs in minor ways. See `The Emacs Lisp Reference Manual'
for how to make more far-reaching changes.
All kinds of customization affect only the particular Emacs session
that you do them in. They are completely lost when you kill the Emacs
session, and have no effect on other Emacs sessions you may run at the
same time or later. The only way an Emacs session can affect anything
outside of it is by writing a file; in particular, the only way to make
a customization `permanent' is to put something in your `.emacs' file
or other appropriate file to do the customization in each session.
*Note Init File::.
* Menu:
* Minor Modes:: Each minor mode is one feature you can turn on
independently of any others.
* Variables:: Many Emacs commands examine Emacs variables
to decide what to do; by setting variables,
you can control their functioning.
* Keyboard Macros:: A keyboard macro records a sequence of
keystrokes to be replayed with a single
command.
* Key Bindings:: The keymaps say what command each key runs.
By changing them, you can "redefine keys".
* Keyboard Translations:: If your keyboard passes an undesired code
for a key, you can tell Emacs to
substitute another code.
* Syntax:: The syntax table controls how words and
expressions are parsed.
* Init File:: How to write common customizations in the
`.emacs' file.