How to append contents of multiple files into one file?

Question

Emacs 26.1, Windows 10, Dired+

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

Answer 1

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)
                (buffer-string))
              contents)))
    (write-region (mapconcat #'identity contents "\n")
                   nil (concat dir "result.txt"))))

Answer 2

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.

Answer 3

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:

   (dired-get-marked-files)
   

   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)))
   

   Note:

   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.

Answer 4

...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.

Answer 5

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.

Answer 6

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.