emacs

||Symbols  Text a^2|| -> \norm{Symbols  Text a^2}

in Latex change I defined my own norm environment, using the \usepackage{amsmath} environment, by

\newcommand{\norm}[1]{\left\Vert#1\right\Vert}

Now I wanted to replace every pair || . || with \norm{.}, e.g.

||a^2 - b^2||^2

to

\norm{a^2 - b^2}^2

REGEXP

M-x query-replace-regexp

||\(.*?\)||

with

\\norm{\1}

The .* matches everything in a greedy way, that means a expression like

find duplicate labels

when you get the warning:

There were multiply-defined labels

you could use following reftex command within emacs

M-x reftex-find-duplicate-labels

http://tex.stackexchange.com/questions/8877/warning-there-were-multiply-...

A list of useful commands, which I learned so far in emacs

Run a shell / terminal in emacs

The most similar to the normal shell:

M-x ansi-term

There also exists:

M-x term
M-x shell
M-x eshell

for further information, see this post

To replace numbers in a document with other calculated numbers (e.g. to replace a 20 with 20-10=10, and a 43 with 33), the best is to use

M-x query-replace-regexp

which is bound to

M-C-%  (= M-C-Shift-5).

Or use

M-x replace-regepx

E.g. to subtract 8 from each number in  the string

out_11_14Small.png

do the following:

M-x query-replace-regexp

[Query replace regexp:] \([0-9][0-9]\) RET
[Query replace regexp in region \([0-9][0-9\) with:]   \,(+ -8 \#1) RET

RET = press the return key.

In short:

M-x dired-do-query-replace-regexp

Longer version:

To replace the same regexp, string or word in multiple files go into dired mode

C-x C-f RET

Then you should see a list of files.

Mark the files you want to edit with m.

To mark all files press t (M-x dired-toogle-marks).

In Emacs 24.1, there’s a command

  C-x r N (‘M-x rectangle-number-lines’)

for numbering lines.