Emacs and Unix Tips

To run single shell command, press “Alt+!” (Alt+x shell-command). This is under the menu “Tools‣Shell Command...”.

To remove the resulting split panes, press “Ctrl+x 1” (Alt+x delete-other-windows).

It is very useful to run shell commands while in emacs. For example, suppose you are writing a document or programing, and you need a list of a particular directory's content. Normally, you would switch to a x-term, do ls, copy the result (probably with the mouse), then switch back to emacs, then paste. But with emacs's shell facilities, you can do all these within emacs.

Select a region, then press “Alt+|” (or “Alt+x shell-command-on-region”). For example, select a region, then press “Alt+| wc -w RET”. This will return the number of words in your selection.

You can have the result replace the selected region. To do that, press “Ctrl+u” before the “Alt+|”.

Start the shell by “Alt+x shell”. To run the previous command, press “Alt+p”. (next is “Alt+n”). To start a second shell, type “Ctrl+u Alt+x shell”.

If you use shell often, you can create a alias (defalias 'sh 'shell) or a keyboard shortcut.

You can run ssh inside emacs with emacs's terminal emulator. To start it, press “Alt+x term”. Then, you can run for example telnet, ssh, top, vi. You can even start another emacs. To exit term, press “Ctrl+d”.

In practice, it's better to run these processes outside of emacs in a “real” system-console or terminal-emulator software. Because, once inside a terminal emulator inside emacs, normal emacs keystroke convention won't work because you told emacs to pretend it is a terminal emulator. This makes the user interface complicated.

Note to those curious: besides the commands “shell” and “term”, there are also “terminal-emulator”, and “eshell”. The commands “term” and “terminal-emulator” seem to be similar but are independent. The “eshell” is similar in purpose to “shell”, but written entirely in elisp, so that, if you are on a non-unix system, you can still run unix-like commands with emacs.

Get this lisp code by Tsuchiya Masatoshi at http://namazu.org/~tsuchiya/elisp/shell-command.el

“Alt+x man”. If you want it in color, use “Alt+x woman”.

The “man” relies the unix “man” utility, while “woman” is completely written in elisp.

Press “Ctrl+h i” (Alt+x info). Use mouse or arrow keys to move cursor to a link. Press enter or click to enter that node. Press u for going to the parent node. n for next node, p for previous node, and press l (lower case L) for the last node you visited (like the Back button in browsers). Press TAB to move cursor to the next link. Press q to quit info.

To call the unix grep command, do “ Alt+! grep xyz filename”.

Or, in Emacs, you can use “Alt+x list-matching-lines” or delete-matching-lines. “list-matching-lines” starts from the beginning of file (regardless if there's a region). “delete-matching-lines” works on the region if there is one, else it starts at the cursor point.

To call the unix command: “Alt+! grep -r mySearchStr dir_name”.

To call emacs version, type: “Alt+x grep”.

The difference between calling the unix grep inside emacs and calling emacs's grep, is this: the result of Emac's grep will be nicely colored and linked. Your search string are highlighted, and you can jump to the file by clicking on the file name or press return when the cursor is on the file name.

“Alt+x grep-find”.

The grep-find command will invoke find . -type f -exec grep -nH -e MySearchStr {} /dev/null \;, by first prompting you in minibuffer, and let you modify it if you want, then it'll place the output in a formated and linked way in another pane.

If you use the command often, you can creat a alias or keyboard shortcut. Here's the code to put in your emacs init file:

(defalias 'gf 'grep-find)
(global-set-key (kbd "<f8>") 'grep-find) ; the F8 key

Normally, you would hack up a shell script, or use a combination of find xargs sed awk perl. Or, you can do it with Emacs. The advantage with Emacs is that you can do it interactively. For example, if you want the replacement happen on a case-by-case basis.

Basically, you want to use find-dired to mark the target files. Then, use dired-do-query-replace-regexp to do the actual find and replace. For detail, See Interactively Find and Replace String Patterns on Multiple Files .

“Alt+x find-dired”.

Explanation: In unix, there's a very useful command that list files in a directory with a particular property. For example, if you want to list all files ending in “.html” in a directory and all subdirectories under it, you can do find /Users/jane/ -name "*.html" -print.

However, the result is a textual output. Let's say you want to run a word count “wc” command on all such files. You can use “find”'s option “-exec”, or in combination with “xargs” command. For example: find . -name "*.html" -print | xargs -l -i wc {}.

However, sometimes you want to do several complicated things with this set of files, and you want to do them interactively. For example, some of such files you want to word count, some of them you want to run another command on, and some of them you need to rename, and what to do depends on the previous commands. In this case, it will be useful, to have this list of files shown in emacs's dired mode, then you can use all emacs dired power to manipulate these files.

Type “Alt+`” (tmm-menubar).