Emacs 26.1, Windows 10, Dired+

How to append contents of multiple files in one folder into one file?

6 Answers 6


Here's a function that appends the contents of each file under DIR and writes the results into a result.txt file in the same directory.

(defun append-file-contents (dir)
  (interactive "DDirectory: ")
  (let (contents
        (default-directory dir)
        (files (directory-files dir nil "^\\([^#.~]\\)")))
    (dolist (file files)
      (when (file-regular-p file)
        (push (with-temp-buffer
                (insert-file-contents file)
    (write-region (mapconcat #'identity contents "\n")
                   nil (concat dir "result.txt"))))
  • In folder has 50 text files. Every file with size 5MB. Is this function "append-file-contents" success process all this files? Feb 9, 2019 at 13:18
  • Can you modify your function to be "interactive" with param dir path? And store result to file,e.g. result.txt. Thanks. Feb 9, 2019 at 13:25
  • 1
    I updated the answer. See if that works for you. Maybe try with some test files first.
    – jagrg
    Feb 9, 2019 at 14:49
  • Would you like to re-indent the code so that it'll be more readable?
    – whatacold
    Feb 10, 2019 at 5:05
  • 1
    You're exceeding the number of arguments. Remove the last one. I would also suggest enabling eldoc-mode. It shows you the arglist in the minibuffer. My other solution involves GNU find but I suspect it won't work with Windows.
    – jagrg
    Mar 20, 2019 at 13:53

One way to get it done is Shell Commands in Dired, together with cat:

  1. Open the directory in dired mode with C-x d
  2. Mark the desired files with m
  3. Run a shell command by hitting ! and typing the command: cat ? >> /path/to/accumulate-file.txt

    The ? surrounded with whitespaces means running the shell command once for each marked files, with ? being replaced by the file name.

  • Did you test it with emacs26.1 on Windows 10? Does it work on Windows?
    – Tobias
    Feb 8, 2019 at 11:15
  • I get error message: The process cannot access the file because it is being used by another process. Feb 8, 2019 at 11:21
  • Haven't tested it on Windows yet :( I guess it should work if there is cat, it seems I'm wrong from OP's comment. I am trying to do it in elisp way.
    – whatacold
    Feb 8, 2019 at 11:34
  • I have added an Elsip solution.
    – Tobias
    Feb 8, 2019 at 11:55
  • @Alexei Since you have cat as you mentioned in other comment, then I don't understand why this error. Is there any other app "lock" the files? Does cat work in Git Bash?
    – whatacold
    Feb 8, 2019 at 14:04
  1. Open the buffer where you want to insert the files and put point where you want the text to be inserted.

  2. Find the directory with the files, i.e., C-x C-f. The directory is shown in a dired buffer.

  3. Mark the files with m.

    a. You can also mark with % m if you want to select the files by a regular expression.

    b. You can also use % g if you want to mark files containing matches for a given regular expression.

  4. The basic lisp code that provides you with the list of marked files is:


    The files have the same order as in the dired buffer. You can also sort in other ways with cl-sort.

  5. Insert files from the list into your target buffer. Therefore run the following lisp code with the dired buffer current:

    (dolist (fn (dired-get-marked-files)) (with-current-buffer "target-buffer-name" (insert-file fn)))


    a. You have to replace "target-buffer-name" by the name of your target buffer. Often that is the file name of your target file.

    b. For this command to work the buffer with name "target-buffer-name" must already exists.

    c. If you want to create a new buffer use (get-buffer-create "target-buffer-name") instead.

You can run the elisp expressions in the current buffer easily with the key sequence M-:. You just input the elisp expression in the minibuffer and run it by pressing the RET button.

  • 1
    The docstring of insert-file says: Don’t call it from programs! Use ‘insert-file-contents’ instead. , so maybe insert-file-contents is better?
    – whatacold
    Feb 8, 2019 at 12:11
  • (dired-get-marked-files) seem more intuitive to me to get the file lists, and it returns them as in the buffer top-down.
    – whatacold
    Feb 8, 2019 at 12:18
  • @whatacold Thanks I will replace (dired-map-over-marks ...) by (dired-get-marked-files). I know about insert-file-contents and opted for insert-files because it works and it is shorter. At this point one just needs the job to be done.
    – Tobias
    Feb 8, 2019 at 12:26
  • @whatacold Note that dired-get-marked-files is from dired+.el which is not necessarily installed. Therefore I will add my original solution again.
    – Tobias
    Feb 8, 2019 at 12:33
  • 1
    @Alexei You don't need dired-mode for that. Just use M-! if that works for you. The solution I offered is elisp only and works independently of the OS.
    – Tobias
    Feb 8, 2019 at 14:23

...And then there is the Eshell-way. It uses Elisp under the hood when needed. Therefore it is OS-independent:

  1. Open an Eshell via M-x eshell.

  2. Change directory in the Eshell to the one you want with cd YourDirectoryPath.

  3. Concatenate all files you want in Eshell with cat Pattern*Of*Source*Files > targetFile.

Note, emacs -Q uses Elisp for all above steps under Ubuntu (WSL):

~ $ which cd
eshell/cd is a compiled Lisp function in ‘em-dirs.el’.
~ $ which cat
eshell/cat is a compiled Lisp function in em-unix.el.

For completeness, as sometimes the crudest of methods is the most appropriate...

  1. Open the second file using C-x C-f (find-file)
  2. Select the entire contents using C-x h (mark-whole-buffer)
  3. Copy the text using M-w (kill-ring-save)
  4. Open the first file using C-x C-f (find-file)
  5. Move to the end of the buffer using M-> (end-of-buffer)
  6. Paste the text from the first file using C-y (yank)

At this point, you could save over the original first file using C-x C-s (save-file) or save a copy using C-x C-w (write-file). Repeat this as needed for all the files.

  • In folder I has 50 files. So I don't want to repeat 6 steps 50 times! Feb 8, 2019 at 13:47
  • And why not!? ;) Feb 8, 2019 at 13:48
  • "mark-whole-buffer" The problem that this 50 files are large. So mark whole buffer is very slow and maybe not work correct. Feb 8, 2019 at 13:49
  • By "cat" command I can add to one file content of all e.g. java files in current folder and all subfolders like this: find . -type f -name "*.java" -exec cat {} \; > result.txt Mar 19, 2019 at 16:10

Open file1.txt using C-x C-f (find-file). Press M-! to execute shell-command. The command you want to execute is copy:

copy /b file1.txt + file2.txt + file2.txt file1.txt

Reload the buffer using M-x revert-buffer to see that indeed the files were appended. Beware! The copy command will overwrite file1.txt.

If you don't have file1.txt open, then the default-directory will not be for the correct folder. You would need to either issue cd first to change the default directory for the current buffer or use absolute paths.

  • 1
    In dired mode M-!. Then use command: cat trace* > result.txt . This command copy content of all file with names trace* to ONE file result.txt Feb 8, 2019 at 13:43
  • I don't think that default Windows 10 has cat. If you have Gitbash installed, though, then you do and it's likely on the path. You could use type, though. stackoverflow.com/questions/60244/… Feb 8, 2019 at 13:48
  • 1
    I has Git. As result I has cat on my Windows machine. Feb 8, 2019 at 13:48

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