emacs - working with lines

Table of Contents

Emacs keep or remove lines matching regex
Joining lines in emacs
Sorting lines alphabetically
Delete duplicate lines
Delete empty lines
- To do it in a region or on the whole buffer.
- Clean up empty lines specifically where you want it but not on a region or not on the whole buffer

Emacs keep or remove lines matching regex

You can use keep-lines to get what you want, copy them, and then undo.

For the opposite, there is also flush-lines to get rid of lines you don’t want.

Joining lines in emacs

How to join lines into one in emacs?

There are several ways to do this.

~Meta ^~

Either visually select and call Meta ^ to join the visually selected lines. Or place the point anywhere on the last line of the group of lines that need joining and call Meta ^ repeatedly until all the lines are merged. It leaves one space between all of the now joined lines.
~Meta join-line~ : This will join two lines. Bind it to a convenient keystroke.
Select paragraph/lines by ~Meta h~ or ~Ctrl SPC~. Press ~Meta q~
Multiple Cursors combined with ~Meta ^~ will collapse all selected lines into one with all extraneous white-space removed.

For example to select an entire buffer, invoke multiple cursors mode, collapse into one line, and then disable multiple cursors mode:
```
C-x h
M-x mc/edit-lines
M-^
C-g
```

Sorting lines alphabetically

Imagine you’re working in emacs. You come across this code:

gem 'clearance', '1.0.0.rc4'
gem 'neat'
gem 'stripe'
gem 'pg'
gem 'thin'
gem 'rails', '3.2.11'
gem 'bourbon'
gem 'simple_form'
gem 'strong_parameters'

If you want to sort the list alphabetically, select the lines visually and run: M-x sort-lines

That will result in this:

gem 'bourbon'
gem 'clearance', '1.0.0.rc4'
gem 'neat'
gem 'pg'
gem 'rails', '3.2.11'
gem 'simple_form'
gem 'stripe'
gem 'strong_parameters'
gem 'thin'

Delete duplicate lines

M-x delete-duplicate-lines

this works on a region, not a buffer, so select the desired text first
it maintains the relative order of the originals, killing the duplicates

Delete empty lines

To do it in a region or on the whole buffer.

M-x flush-lines (delete lines containing matches for REGEXP)
For regex for empty lines, enter this: ^$

^ represents the beginning text of the line $ represents the ending text of the line

Clean up empty lines specifically where you want it but not on a region or not on the whole buffer

C-x C-o

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