I am slightly confused by the difference between keys and key-bindings in emacs after reading the first chapter of "Writing GNU Emacs Extensions" (O'Reilly book).
The chapter starts by noting that in some emacs version the keys backspace and DEL, invoke the help menu instead of deleting. In other words, they invoke what is invoked by C-h.
The chapter then goes on to show how to change this behaviour using Lisp code. This is done by binding the keystroke C-h to the delete command.
This is a bit confusing to me. In my mind DEL, Backspace and C-h are three different keystrokes (the first two consisting of a single key).
Why does remapping C-h effect what DEL and Backspace does?
I would have thought to change what backspace does for example, you would remap backspace to another command, not the keystroke C-h.
Unless remapped by a low-level keybord driver, the effect of the Backspace key is to send the character with numeric code 8, which, in certain operating systems, is exactly the same code generated by pressing Control-h. You can verify this fact by simply writing anything on a unix (or linux) shell and then pressing Backspace and Control-h: both of them have the effect of erasing the previous character, since the character with numeric code 8 is interpreted by the operating system as the control character BS, backspace, used either to erase the last character printed or to overprint it (see wikipedia). Analogously, Control-J is equivalent to the RETURN key, etc.
The same Wikipedia page describe DEL as “originally intended to be an ignored character, but now used in some systems to erase a character”.
So, when you assign a command to a keystroke you are actually assigning a command to a character code, and if two or more keys generate the same code, by pressing them you are invoking the same command.
#Renzo answered your question about how these keys are related and how binding one can seem to affect another. Here is some more information about what's going on in this particular case.
See the Emacs manual, node DEL Does Not Delete.
There you will see this, following an explanation of the problem/confusion:
To fix the problem in every Emacs session, put one of the following
lines into your initialization file (*note Init File::). For the first
case above, where BACKSPACE deletes forwards instead of backwards, use
this line to make BACKSPACE act as DEL:
(normal-erase-is-backspace-mode 0)
For the other two cases, use this line:
(normal-erase-is-backspace-mode 1)
Another way to fix the problem for every Emacs session is to
customize the variable normal-erase-is-backspace: the value t
specifies the mode where BS or BACKSPACE is DEL, and nil
specifies the other mode. *Note Easy Customization::.
See also the GNU Emacs FAQ question about Backspace invoking help. There you will see, in addition to information similar to that above, information about how to remap DEL on UNIX - use this:
stty erase '^?'
Wrt C-j and RET (not mentioned in the question, but mentioned in #Renzo's answer): The default behavior of Emacs changed in most programming modes, in Emacs 24.4.
Starting with that release, electric--indent-mode is turned on by default, which means that RET inserts a newline character and indents, whereas C-j just inserts a newline character. Prior to that release, these keys had the opposite behaviors. If you prefer the old behavior then do this, to turn off electric-indent-mode:
(when (fboundp 'electric-indent-mode)
(electric-indent-mode -1)) ; Use classic `C-j' and `RET'.
Related
In the graphical mode, RET does the same as C-m, namely newline.
However, when I use M-a or M-e, they seem to distinguish between them. The newline produced by RET, they skip all to a double-RET point, and with the newline produced by C-m, they move the cursor line by line. Why so?
Description (C-h k) for both keys shows the same.
If it matters, it is Emacs23.3.1 on Ubuntu 12.04.
The answer could be dependent on the mode you're in as well as in the key codes generated by your operating system. When I hit Ctrl-h k Ctrl-m in the *scratch* buffer on my Windows box, I'll get the info for (newline) with the information that it is bound to RET. Theoretically, in some other mode, C-m and RET could be set to different functions. This requires, of course, that the OS doesn't generate the same key code.
What Emacs writes as RET (or as <RET>) is, yes, the same character as C-m - it is the ASCII control character 13. This is so regardless of what keyboard etc. you have.
However, the logical key (aka "key sequence") that Emacs sees when you hit the phisical (keyboard) key named Enter or Return might be different from RET (aka C-m). To see what key Emacs recognizes when you hit that keyboard key, use C-h k and hit the key. If Emacs says RET then this is the typical case, and yes, hitting that key is then identical to pressing Control and hitting m (assuming the key labeled Control does what it does typically).
In the graphical mode, the answer is yes (unless keys are redefined, of course).
Careful examination of my file showed that the effect I observed was a coincidence. It was exactly in those paragraphs which I C-m'ed that all lines would end in a dot (it was a poem).
Actually, C-h k key description says the same thing for both keys. Thanks to schaueho's answer for pushing me in this direction.
My problem is that I want to bind Control + Backspace combination to backward-delete-word function. However, it doesn't seem possible because emacs doesn't detect the Control key in combination with backspace.
I detected that by looking at the "logger" (C-h l). So if I press Backspace, it shows DEL. If I press Control + Backspace, it still shows DEL.
Is there any way to achieve that?
I have read and tried other questions, but couldn't fix it.
As #phils pointed out, if you are using Emacs in a terminal (e.g. emacs -nw) instead of as a GUI (no -nw command-line option), and if you are not on MS Windows, then by default certain key sequences are not available to you.
However, it might still be possible for you to configure the terminal (e.g., xterm) so that it in fact supports some such key sequences for Emacs. See this comment by the Emacs maintainer in the discussion of Emacs bug #10387.
(That said, you might find it simpler to just use a different key sequence. Or switch to the GUI version of Emacs.)
In emacs (ver. 24.3), I have my forward-paragraph and backward-paragraph mapped to M-p and M-n instead of M-{ and M-}. It is easier for me to remember and use fluidly with C-p and C-n. I've recently started using multi-term to run most of my terminal work. However, when I switch to line-mode my custom bindings for forward and backward paragraph no longer work. It says 'empty input ring'. Oddly when I'm in char-mode, the C-p and C-n do what they are supposed to do (bringing up previous prompt entries), but my paragraph movements work.
So in short, my custom forward and backward paragraph bindings work in char-mode (where I don't really need them), but not in line-mode. Any ideas?
See term-bind-key-alist, which includes C-p, C-n, M-p, and M-n by default. See also these passages from the EmacsWiki page MultiTerm. The second especially seems relevant to your problem. These do not mention term-line-mode or term-char-mode, but I think they might give you a place to start.
Note 1
‘term-unbind-key-list’ is a list of keys which emacs keeps for itself. By default it contains (“C-z” “C-c” “C-x” “C-h” “C-y” “”)
‘term-bind-key-alist’ is a list of keys and functions which you can use, for example to use Emacs style cursor movement to the multi-terminal. The default is long, so I’ll let you look it up yourself.
Note 2
Because C-r is default keystroke for isearch-backward, for avoid conflict with C-r, i binding M-r to send “C-r” character to shell.
You can use option term-bind-key-alist/term-unbind-key-list to binding/unbinding special keystroke in multi-term.el, and don’t use term-mode-hook. ☺ –- AndyStewart
Also, I don't see term-line-mode anywhere in multi-term.el. It looks as if it makes use only of term-char-mode. See, for instance, multi-term-keystroke-setup.
Can anyone advise how I can move forward (or back) by n commas in emacs?
I am trying to navigate my way through a CSV file
I am aware I can do something like:
C-u 100 M-f
but being able to do something more reg-exp like specifically on commas would be more accurate
The other thing I tried was combining C-u # and C-s , but that didn't work
It will with a keyboard macro, which you can define interactively.
C-x( -- start recording
C-s,RET -- search for a comma (the RET is important; see below)
C-x) -- stop recording
You can now execute that macro again with C-xe (and then just e for continued single repetitions), or use a prefix argument to repeat it a given number of times:
C-u 100 C-xe
Keyboard macros are tremendously useful, and can be easily bound to keys, or even added to your .emacs file in elisp form if you want to keep one for future use. See the manual for details.
edit:
More seamlessly for ad-hoc macros, you can supply the prefix argument when you stop the recording to get exactly that many repetitions, including the one used to record it:
C-x(C-s,RETC-u 100 C-x)
I was seeing some unexpected behaviour with that sequence before I added the RET to explicitly invoke isearch-exit before stopping recording. It behaved as if it was only recording and repeating the comma key (leading to the comma being inserted many times instead of being searched for many times).
Using edit-last-kbd-macro after recording, I could see there was a quirk when using isearch in a macro, such that the C-x typed when stopping the recording is actually included in the macro definition, which was presumably causing the problem for this particular method of invocation. Similarly with the alternate F3 and F4 bindings (in that case, F4 ends up in the definition). I don't know whether this is a bug or a feature, but apparently it pays to exit the isearch before stopping the macro recording!
p.s. Although the two sets of macro recording bindings aren't identical in all respects, everything here also works with F3 and F4, so for this example you could slightly more concisely use F3C-s,RETC-u 100 F4
With
iy-go-to-char you
can do M-3C-cf, to go to
the third comma.
Use CSV mode which will give you convenient functions to do what you want and more
You could record a macro with C-u C-u M-f or C-u C-u C-f and use that. If it's infrequently used, record it using PF3 and play it back by pressing PF4.
In GNU screen, I want to change the default command binding to Alt-s (by tweaking .screenrc) instead of the default C-a, the reason is I use emacs hence GNU screen binds the C-a key, sending "C-a" to the emacs becomes tedious (as #Nils said, to send "C-a" I should type "C-a a"), as well as "C-a" in bash shell, and I could change the escape to C- but some of them are already mapped in emacs and other combinations are not as easy as ALT-s . If anyone has already done a ALT key mapping, please do let me know.
It is possible to work around :escape command limitations using registers and :bindkey command. Just put this in .screenrc:
# reset escape key to the default
escape ^Aa
# auxiliary register
register S ^A
# Alt + x produces ^A and acts as an escape key
bindkey "^[x" process S
## Alt + space produces ^A and acts as an escape key
# bindkey "^[ " process S
See http://adb.cba.pl/gnu-screen-tips-page-my.html#howto-alt-key-as-escape
From my reading of man screen it seems like the only meta character that screen can use for the command binding is CTRL:
escape xy
Set the command character to x and the character generating a literal
command character (by triggering the "meta" command) to y (similar to
the -e option). Each argument is either a single character, a two-character
sequence of the form "^x" (meaning "C-x"), a backslash followed by an octal
number (specifying the ASCII code of the character), or a backslash followed
by a second character, such as "\^" or "\\". The default is "^Aa".
If there is some mapping that you don't use in emacs, even if it's inconvenient, like C-|, then you could use your terminal input manager to remap ALT-X to that, letting you use the ALT binding instead. That would be a little hackish though.
I'm an Emacs and screen user as well. Although I rarely use Emacs in a terminal -- and as such in a screen session -- I didn't want to give up C-a for the shell either (which uses Emacs key bindings). My solution was to use C-j as the prefix key for screen, which I was willing to sacrifice. In Emacs programming modes it is bound to (newline-and-indent) which I bound to RET as well, so I really don't miss it.
By the way: I know this is an advise rather than an answer, but I felt this would be valuable enough to post nevertheless.
To make Alt+X the default prefix for commands and free C-a, add the following lines to .screenrc:
escape ^||
bindkey "^[x" command
As a side effect C-| will be command prefix too. If you need this keys to be free too, then fix "escape ^||" accordingly.
Screen doesn't have any shorthand syntax for alt bindings, but you can give it the octal code directly. For instance on my machine, Alt-x has the hex code F8, or 370 octal, so putting
escape \370x
in my screenrc changed the escape code to alt-X
Tested and works with screen 4.00.03 on Linux.
You may have to change the escape, since I think this may depend on things like your language and codeset, etc: how I found out what my escape code was was to type
$ echo -n ^QM-x | perl -ne 'printf "%lo\n", ord($_)'
^Q is the quoted-insert command for readline (it inserts what you type directly without trying to interpret it) and M-x was a literal Alt-X.
Fellow emacs user here.
The best solution I've found is a ~/.screenrc file with the following:
# C-a :source .screenrc
escape ^gg
Live updated here: https://gist.github.com/1058111
See also: http://ubuntuforums.org/showthread.php?t=498675
Something I have had for years in my .screenrc:
escape ^Zz
which is now hardwired in muscle memory for me.
Somehow I ended up having to share a screen with someone else's config, and now I keep stopping processes all the time (bash ^Z)... Not funny...