I need to concatenate path string as follows, so I added the following lines to my `.emacs` file:

    (setq org_base_path &quot;~/smcho/time/&quot;)
    (setq org-default-notes-file-path (concatenate &#39;string org_base_path &quot;notes.org&quot;))
    (setq todo-file-path (concatenate &#39;string org_base_path &quot;gtd.org&quot;))
    (setq journal-file-path (concatenate &#39;string org_base_path &quot;journal.org&quot;))
    (setq today-file-path (concatenate &#39;string org_base_path &quot;2010.org&quot;))

When I do &lt;kbd&gt;C-h v&lt;/kbd&gt; `today-file-path` &lt;kbd&gt;RET&lt;/kbd&gt; to check, it has no variable assigned. 

What&#39;s wrong with my code? Is there any other way to concatenate the path string?

## EDIT
I found that the problem was caused by the wrong setup, the code actually works. Thanks for the answers which are better than my code.

Concatenate strings in elisp

Often, when I switch branches in git, if the files are open in emacs, then emacs asks if I want to revert them (as it thinks they&#39;ve changed on disk) even though the contents are identical.

Firstly I&#39;d like to find a way for emacs to not ask me about it at all if the contents on disk are identical to those in the buffer.

Secondly I&#39;d like a command that reverted (without query) all my open buffers that have no unsaved changes, and queried me about those that do have unsaved changes.

Alternatively, I&#39;d be open to suggestions about other solutions, ways of working, etc I could try.  I&#39;m fairly happy writing emacs-lisp if people can give me pointers on where to start.

PS I&#39;m using Aquamacs on OSX if that matters.

Edit:

Well, I&#39;ve found the revbuffs package to be pretty much what I need.  Certainly enough to stop me wanting to try and write anything new myself.  (I mapped revbuffs to Cmd-R which works quite nicely. Kind of similar to Cmd-R in other Mac apps).

Global-auto-revert mode would have been a perfectly fine solution, and I wish I could choose two answers.  I prefer revbuffs simply because of a, possibly irrational, feeling of wanting to be in control of what happens.

I&#39;d kind of guessed that if I accessed git from within emacs, then it could probably be handled easier, but I currently prefer accessing git through the commandline.  (I haven&#39;t quite been using emacs long enough to make it my operating system).  I will investigate magit a little more thoroughly though.

Edit2:

I&#39;ve been using magit for a year now and can highly recommend it for dealing with git from within emacs.  However I still use revbuffs whenever I do a rebase outside of emacs.

How can I get Emacs to revert all unchanged buffers when switching branches in git?

I&#39;ve switched computers a few times recently, and somewhere along the way I lost my .emacs.  I&#39;m trying to build it up again, but while I&#39;m at it, I thought I&#39;d pick up other good configurations that other people use.

So, if you use Emacs, what&#39;s in &lt;i&gt;your&lt;/i&gt; .emacs?

Mine is pretty barren right now, containing only:

1. Global font-lock-mode! `(global-font-lock-mode 1)`
2. My personal preferences with respect to indentation, tabs, and spaces.
3. Use cperl-mode instead of perl-mode.
4. A shortcut for compilation.

What do you think is useful?

What&#39;s in your .emacs?

In GNU emacs, every time I hit &lt;kbd&gt;Ctrl-x Ctrl-b&lt;/kbd&gt; to see all of my buffers, the window is split to show the buffer list, or if I have my window already split in 2 (for instance, I will have a shell running in the lower window), the buffer list appears in the other window. 

My desired behavior is for the buffer list to appear in my active window so that I can select the buffer I want and continue to working in the same window, rather than having to &lt;kbd&gt;Ctrl-x Ctrl-o&lt;/kbd&gt; to the other buffer, selecting the buffer (with &lt;kbd&gt;enter&lt;/kbd&gt;) and editing that buffer in the other window... I&#39;ve googled for it but it doesn&#39;t seem to be a common desire? I wonder if anyone has an elispy (or other) solution?

emacs list-buffers behavior

I have a non-emacs global search and replace function that causes my disk files to become more up-to-date than my emacs buffers (en masse).  Is there any way to tell emacs to refresh all the buffers from disk in one fell swoop, instead of having to do each one individually by reloading the file?

Thanks!
D

How to have Emacs auto-refresh all buffers when files have changed on disk?

Frequently, I&#39;ve dug into apropos and docs looking for something like the following only to give up to get back to the task at hand:


(repeat-last-command)

do the last C- or M- command I just executed (to be rebound to a fn key)

or sometimes the related: 


(describe-last-function)

what keystroke did I just mistakenly issue, the effect of which I&#39;d like to add to my bag of tricks. describe-key is close, but requires knowing what I typed. 


Am I simply asking too much from my trusty sidekick?

Is there a (repeat-last-command) in Emacs?

I have decided to check out Emacs, and I liked it very much. Now, I&#39;m using the [Emacs Starter Kit][1], which sort of provides better defaults and some nice customizations to default install of Emacs.

I have customized it a little, added some stuff like [yasnippet][2], [color-themes][3], [unbound][4], and other stuff. I&#39;ve set up a [github repository][5] where I keep all of the customizations so I can access them from multiple places or in case something goes bad and I lose my .emacs.d directory.

All of this is very nice, but there is a problem: Emacs takes about 1-2 seconds to load. AFAIK I can compile individual .el files with M-x byte-compile-file to .elc, and it works. But there are a lot of .el files, and I wonder if there is a way to compile them all with a simple command or something, to speed up the loading of Emacs. My Emacs is not always open, and I open and close it quite frequently, especially after I&#39;ve set it up as a default editor for edit command in Total Commander to get used to it faster (yeah, windows xp here).

My Emacs version is 22.3. And yes, the default Emacs installation without any customizations fires up instantly.

I am not sure which version is preferred when loading, the .el or compiled .elc one by the way O.o

So, is there an elisp command or Emacs command line switch to make Emacs byte-compile everything in .emacs.d directory?


  [1]: http://github.com/technomancy/emacs-starter-kit/tree/master
  [2]: http://code.google.com/p/yasnippet/
  [3]: http://www.nongnu.org/color-theme/
  [4]: http://www.emacswiki.org/emacs/unbound.el
  [5]: http://github.com/Irwin1138/emacs-starter-kit/tree/master

How do I byte-compile everything in my .emacs.d directory?

What&#39;s the best way to achieve something like code folding, or the type of cycling that org-mode uses.  What would be the best solution in elisp to create this type of behavior?

EDIT:
I&#39;m sorry I was not clear.  I want to program something in elisp that does things very similar to code folding, or actually most like org-mode with the hierarchy that can be expanded.  I am wondering the best way to achieve this effect.  I think I have heard emacs overlays are a good solution, but I don&#39;t know.

As far as folding I just use the builtin set-selective-display

EDIT NUMBER 2:

Thanks for the answers but I think I am asking the wrong question so let me try to be more clear on what I am trying to do.  I would like to create the following

When you put your point on a function and call this elisp function it will put the function definition from wherever it is (I am thinking of just using find-tag for this) and unfold it in the current buffer.  The idea is if you have to jump to a different buffer to read the function definition I feel like it&#39;s a context switch to another file.  So I would like it to behave like code folding only it pulls in code external from the buffer.  This presents some problems as it can not actually paste the code into the buffer or if someone saves it will save the pulled in code.  So I am wondering if there is a way to create an area inside a buffer that is also not part of the buffer.  I think that makes sense.

How to achieve code folding effects in Emacs?

I&#39;ve been updating my emacs config with the use of Rsense to allow for an autocomplete drop down box to appear whilst typing code.  This works well in most files except I&#39;ve found it doesn&#39;t allow me to select an answer from the table when I&#39;m editing some code in my ruby on rails project.

Here is my setup:
https://github.com/map7/simple_emacs

I&#39;m using this under Ubuntu 10.04.

For simple ruby script files it works great. I can open up a new file and type.

&lt;!-- language: lang-rb --&gt;

    &quot;test&quot;.up...

Just as I type the &#39;p&#39; character in up a list of options appear and I can go up and down the list with arrow keys and select one (eg: upcase) with the enter key.

What doesn&#39;t work is when I do the exact same test but within a rails project&#39;s base directory.

**Update:**

Found that the problem is with (require &#39;rails), so it&#39;s something in the emacs-rails plugin that the autocomplete doesn&#39;t like.

**Update:** 

It&#39;s within emacs-rails -&gt; rails-project.el. If I comment this macro out then autocomplete works, otherwise it doesn&#39;t:

&lt;!-- language: lang-rb --&gt;

    (defmacro* rails-project:with-root ((root) &amp;body body)
      &quot;If you use `rails-project:root&#39; or functions related on it
    several times in a block of code, you can optimize your code by
    using this macro. Also, blocks of code will be executed only if
    rails-root exist.
     (rails-project:with-root (root)
        (foo root)
        (bar (rails-core:file \&quot;some/path\&quot;)))
     &quot;
     `(let ((,root (rails-project:root)))
        (when ,root
          (flet ((rails-project:root () ,root))
            ,@body))))


Can someone explain why this breaks autocomplete?

Emacs Ruby autocomplete almost working

What does this do? 

    (add-hook &#39;compilation-mode-hook #&#39;my-setup-compile-mode)

...and is it different than

    (add-hook &#39;compilation-mode-hook &#39;my-setup-compile-mode)



emacs/elisp: What is the hash (pound, number sign, octothorp) symbol used for?

I need to get the full path of the file that I&#39;m editing with emacs.

 * Is there a function for that?
 * If not, what would be the elisp function for getting that?
 * How can I copy the result (path name) to a clipboard so that I can reuse it?

I&#39;m using Mac OS X and Aqumacs. 

    (setq filepath (get-fullpath-current-file)) ???
    (copy-to-clipboard &#39;filepath) ???

## ADDED
&lt;pre&gt;
(defun show-file-name ()
  &quot;Show the full path file name in the minibuffer.&quot;
  (interactive)
  (message (buffer-file-name))
  (kill-new (file-truename buffer-file-name))
)
(global-set-key &quot;\C-cz&quot; &#39;show-file-name)
&lt;/pre&gt;

Combining the two answers that I got, I could get what I want. Thanks for the answers. And some more questions.

 * What&#39;s for (file-truename)?
 * Can I copy the path name to System(OS)&#39;s clipboard, not the kill ring so that I can use the info with the other apps?

The function to show current file&#39;s full path in mini buffer

I&#39;m trying to detect the size of the screen I&#39;m starting emacs on, and adjust the size and position the window it is starting in (I guess that&#39;s the frame in emacs-speak) accordingly. I&#39;m trying to set up my &lt;tt&gt;.emacs&lt;/tt&gt; so that I always get a &quot;reasonably-big&quot; window with it&#39;s top-left corner near the top-left of my screen.

I guess this is a _big_ ask for the general case, so to narrow things down a bit I&#39;m most interested in GNU Emacs 22 on Windows and (Debian) Linux.


How do I set the size of Emacs&#39; window?

I often want to unsplit window as follows:

    +--------------+-------------+			   +--------------+-------------+
    |              |             |			   |              |   	       	|
    |              |             |			   |              |   	       	|
    |              |             |			   |              |   	       	|
    +--------------+             |     --&gt;	   |              |   	       	|
    |              |             |			   |              |   	       	|
    |              |             |			   |              |            	|
    |              |             |			   |              |             |
    +--------------+-------------+			   +--------------+-------------+



    +--------------+--------------+			   +-----------------------------+
    |              |              |			   |                             |
    |              |              |			   |                             |
    |              |              |			   |                             |
    +--------------+--------------+    --&gt; 	   +-----------------------------+
    |                             |			   |                             |
    |                             |			   |                             |
    |                             |			   |                             |
    +-----------------------------+			   +-----------------------------+

Currently, I start with &lt;kbd&gt;ctrl&lt;/kbd&gt;-&lt;kbd&gt;x&lt;/kbd&gt; &lt;kbd&gt;1&lt;/kbd&gt; and then split vertically/horizontally. but my real qustion is how can one remove a particular window split with out disturbing the other window structure? Is there any elisp function in built?

emacs, unsplit a particular window split

In Emacs Lisp, how do I check if a variable is defined?

How do I programmatically determine which OS Emacs is running under in ELisp?

I would like to run different code in `.emacs` depending on the OS.

How to determine operating system in elisp?

I have a question about Emacs Lisp. What is the difference between **setq** and **setq-default**?

Tutorials say **setq** takes effect in the *local buffer* while **setq-default** affects all buffers.  
 
For example, if I wrote **(setq a-var a-vars-value)** in **init.el**, I found after starting Emacs and opening a new buffer, the **a-var** is also there and its value is **a-vars-value**. I thought it was not supposed to be there. It seems there is no difference between **setq** and **setq-default**.  

Is there something wrong with my understanding?

For example:  

1. I wrote **(setq hello 123)** in the **init.el** file, and I run **emacs abuffer** in the shell, then I input **&quot;hello C-x C-e&quot;**, it shows &quot;123&quot;. The same happens when I run this in all new buffers.  

2. I wrote **(setq tab-width 4)** in the **init.el** file. When I run **tab-width C-x C-e**, it shows &quot;8&quot; (Current mode is &#39;Text&#39;). However, when I use **(setq-default tab-width 4)**, it show &quot;4&quot;. I can&#39;t explain this phenomenon.

The difference between setq and setq-default in Emacs Lisp

How do I close all but the current buffer in Emacs? Similar to &quot;Close other tabs&quot; feature in modern web browsers?

Close all buffers besides the current one in Emacs

I am getting a &quot;Wrong type argument: commandp, (lambda nil (forward-line 5))&quot; here.

    (global-set-key [?\M-n] (lambda () (forward-line 5)))

What is the error? I&#39;m fairly sure it&#39;s simple &amp; I&#39;m missing something obvious.

&quot;Wrong type argument: commandp&quot; error when binding a lambda to a key

I am currently using GNU Emacs 23.0.93.1 in Windows Vista SP1. In my .emacs file I make a call to &lt;code&gt;(server-start)&lt;/code&gt; and that is causing an error with the message *The directory ~/.emacs.d/server is unsafe*. Has anyone seen this and know a fix or workaround? ... other than leaving server turned off ;) 

Here is the stack trace:

    Debugger entered--Lisp error: (error &quot;The directory ~/.emacs.d/server is unsafe&quot;)
      signal(error (&quot;The directory ~/.emacs.d/server is unsafe&quot;))
      error(&quot;The directory %s is unsafe&quot; &quot;~/.emacs.d/server&quot;)
      server-ensure-safe-dir(&quot;~\\.emacs.d\\server\\&quot;)
      server-start(nil)
      call-interactively(server-start t nil)
      execute-extended-command(nil)
      call-interactively(execute-extended-command nil nil)



Emacs - Error when calling (server-start)

Is there a difference between setting things for a mode using `eval-after-load` and using the mode hook?

I&#39;ve seen some code where `define-key` is used inside a major mode hook, and some other code where `define-key` is used in `eval-after-load` form.


-------------


Update:

For better understanding, here is an example of using eval-after-load and mode hooks with org-mode. The code can run **before** `(load &quot;org&quot;)` or `(require &#39;org)` or `(package-initialize)`.


    ;; The following two lines of code set some org-mode options.
    ;; Usually, these can be outside (eval-after-load ...) and work.
    ;; In cases that doesn&#39;t work, try using setq-default or set-variable
    ;; and putting them in (eval-after-load ...), if the
    ;; doc for the variables don&#39;t say what to do.
    ;; Or use Customize interface.
    (setq org-hide-leading-stars t)
    (setq org-return-follows-link t)

    ;; &quot;org&quot; because C-h f org-mode RET says that org-mode is defined in org.el
    (eval-after-load &quot;org&quot;
      &#39;(progn
         ;; Establishing your own keybindings for org-mode.
         ;; Variable org-mode-map is available only after org.el or org.elc is loaded.
         (define-key org-mode-map (kbd &quot;&lt;C-M-return&gt;&quot;) &#39;org-insert-heading-respect-content)
         (define-key org-mode-map (kbd &quot;&lt;M-right&gt;&quot;) nil) ; erasing a keybinding.
         (define-key org-mode-map (kbd &quot;&lt;M-left&gt;&quot;) nil) ; erasing a keybinding.
                 
         (defun my-org-mode-hook ()
           ;; The following two lines of code is run from the mode hook.
           ;; These are for buffer-specific things.
           ;; In this setup, you want to enable flyspell-mode
           ;; and run org-reveal for every org buffer.
           (flyspell-mode 1)
           (org-reveal))
         (add-hook &#39;org-mode-hook &#39;my-org-mode-hook)))


eval-after-load vs. mode hook

How can I convert a symbol type into a string in Emacs lisp? 

I wasn&#39;t able to find a `symbol-to-string` function or anything similar.

Convert Symbol to a String in Elisp

Is there a builtin command to clear shell while using shell in emacs?

If not, is there an elisp function to achieve the same?

Command to clear shell while using emacs shell

In elisp, there is an &#39;if&#39; case where I would like to perform many different things:

    (if condition
        (do-something)
        (do-something-else)
        ...)

However, (do-something-else) is executed in the else-case only.  How can you specify a block of instructions to execute?  For example:

    (if condition
        (begin
            (do-something)
            (do-something-else)
            ...))

How can you write multiple statements in elisp &#39;if&#39; statement?

In vi[m] there is the [`!` command which lets me pipe text][1] through a shell command -- like sort or indent -- and get the filtered text back into the buffer. Is there an equivalent in emacs?

  [1]: http://www.softpanorama.org/Editors/Vimorama/vim_piping.shtml

Filtering text through a shell command in Emacs

I would like emacs to mark files that are generated as read-only when they&#39;re opened.  The part of the puzzle that I&#39;m missing is how to check if a file &quot;exists&quot;.  I currently have the following:

    ;;
    ;; get file extension
    ;;
    (defun get-ext (file-name)
      (car (cdr (split-string file-name &quot;\\.&quot;))))

    ;; 
    ;; get the base name of the file
    ;;
    (defun base-name (file-name)
      (car (split-string file-name &quot;\\.&quot;)))

    ;;
    ;; if an &#39;lzz&#39; file exists for this header, mark it as read only
    ;;
    (defun mark-read-only ()
      (if (string= (get-ext (cur-file)) &quot;h&quot;)
          (if ( ??file-exists??? (concat (base-name (cur-file)) &quot;.lzz&quot;) )
              (toggle-read-only))))

What can I use for &quot;???file-exists???&quot;?

Once I find this, I&#39;ll add &quot;mark-read-only&quot; to the appropriate hook (which I think is the find-file-hook).

**BACKGROUND**

We use [lzz][1] as a code generator to simplify our C/C++ development process.  Briefly, lzz takes a single input file (which looks very like C/C++) and generates header and source files as appropriate.

By default, lzz includes #line directives so that the debugger points to the original source and not the generated source, however, to reduce compilation dependencies we normally disable these directives in header files.  The result is that when debugging templates or inline functions, the debugger normally points to the generated header file and not the original source file.

This is not a big deal, however, recently I&#39;ve found that when debugging I&#39;ll make a quick modification to the displayed file and then I&#39;ll rebuild.  Of course this normally means that the change I made disappears because the file I edited is generated and so the changes are &quot;blown away&quot; during the library rebuild.

**SOLUTION**

Thanks to everyone for their help and comments.  A special thanks to [cobbal][2] for pointing out the correct function to use.

Here&#39;s the resulting code (with updates based on the other comments here too):

    (defun cur-file ()
      &quot;Return the filename (without directory) of the current buffer&quot;
      (file-name-nondirectory (buffer-file-name (current-buffer)))
      )

    (defun mark-generated-as-read-only ()
      &quot;Mark generated source files as read only.
    Mark generated files (lzz or gz) read only to avoid accidental updates.&quot;
      (if
          (or (string= (file-name-extension (cur-file)) &quot;h&quot;)
              (string= (file-name-extension (cur-file)) &quot;cpp&quot;))
          (cond
           (
            (file-exists-p (concat (file-name-sans-extension (cur-file)) &quot;.lzz&quot;))
            (toggle-read-only))
           (
            (file-exists-p (concat (file-name-sans-extension (cur-file)) &quot;.gz&quot;) )
            (toggle-read-only))
           )
        )
      )

   [1]: http://www.lazycplusplus.com/
   [2]: https://stackoverflow.com/users/73681/cobbal

How can I check if a file exists using Emacs Lisp?

How can I create an empty file from emacs, ideally from within a dired buffer?

For example, I&#39;ve just opened a Python module in dired mode, created a new directory, opened that in dired, and now need to add an empty `__init__.py` file in the directory.

If I use `C-x C-f __init__.py RET C-x C-s` then emacs doesn&#39;t create the file because no changes have been made to it.  I would have to type in the file, save it, delete my typing and then save it again for that to work.

Thanks

How do I create an empty file in emacs?

Normally the easiest way to debug is using `printf`. What can I do to debug emacs-lisp? How can I print something to emacs editor from elisp? Or *is there any way to debug elisp code?*

For example, how can I check if the following code is run in `.emacs` file?

    (load &quot;auctex.el&quot; nil t t)

How to debug elisp?

Suppose I have variables `dir` and `file` containing strings representing a directory and a filename, respectively . What is the proper way in emacs lisp to join them into a full path to the file?

For example, if `dir` is `&quot;/usr/bin&quot;` and `file` is `&quot;ls&quot;`, then I want `&quot;/usr/bin/ls&quot;`. But if instead `dir` is `&quot;/usr/bin/&quot;`, I still want the same thing, with no repeated slash.

What is the correct way to join multiple path components into a single complete path in emacs lisp?

I have tried to search Google and look in the manual, but still cannot find how to get major mode of a buffer object.  Can you help me with an example or a reference.  Thanks

only solution I could find was to query major-mode after changing the buffer and then changing back to original buffer. Is there a better way to do it?

emacs lisp, how to get buffer major mode?

I&#39;ve learned Clojure previously and really like the language. I also love Emacs and have hacked some simple stuff with Emacs Lisp. There is one thing which prevents me mentally from doing anything more substantial with Elisp though. It&#39;s the concept of dynamic scoping. I&#39;m just scared of it since it&#39;s so alien to me and smells like semi-global variables. 

So with variable declarations I don&#39;t know which things are safe to do and which are dangerous. From what I&#39;ve understood, variables set with setq fall under dynamic scoping (is that right?) What about let variables? Somewhere I&#39;ve read that let allows you to do plain lexical scoping, but somewhere else I read that let vars also are dynamically scoped. 

I quess my biggest worry is that my code (using setq or let) accidentally breaks some variables from platform or third-party code that I call or that after such call my local variables are messed up accidentally. How can I avoid this? 

Are there a few simple rules of thumb that I can just follow and know exactly what happens with the scope without being bitten in some weird, hard-to-debug way?


How to live with Emacs Lisp dynamic scoping?

What are some REPLs for Emacs Lisp?

Is there only one that is within Emacs?

Are there some that run inside terminal outside Emacs?


All Elisp Solutions on Gang of Coders

Total of 31 Elisp Solutions