How remove whitespaces in the beginning of lines?

Question

Emacs 26.1

I has the next text:

I need to remove all whitespaces in the beginning of the lines. Every line has different count of whitespaces. The result must be like this:

Answer 1

Another way is just to mark the region and call delete-whitespace-rectangle!

Answer 2

IMHO the standard way is:

1. Go to the top of your buffer.
2. Type C-M-% for query-replace-regexp.
3. Input ^\s-+ as regular expression and RET. (See explanation below.)
4. Leave the replacement string empty, i.e., press RET again.
5. You are prompted by query-replace-regexp in the minibuffer.
   Press ! to perform all replacements at once.

Explanation of the regular expression:

1. The caret ^ stands for the beginning of line.
2. The \s- stands for any character designated as space by the current modes syntax table.
3. The + stands for one or more contiguous matches.

Answer 3

You can use regex inside emacs (C-M-s). Check here emacs regex. By using regex you can write a rule that matches all the blanks that are at the beginning.

Answer 4

Another thing you can do: use M-xalign-regex, then use SPC as input to this command (i.e. align on space), then use rectangle-editing commands: C-x r k for example to delete rectangle before the lines.

This is not terribly efficient, but it's how I do it because I use both commands very often and they are, sort of, automatic for me (muscle memory, or w/e you call it).