ELisp: Functions on Line

Get Position of Beginning of Line

line-beginning-position

(line-beginning-position &optional N)

Return the character position of the first character on the current line.

With optional argument N, scan forward N - 1 lines first.

If the scan reaches the end of the buffer, return that position.

;; return line beginning position
(line-beginning-position)

line-end-position

(line-end-position &optional N)

return the line end position.

Move Cursor to Beginning of Line

beginning-of-line

(beginning-of-line &optional N)

• Move point to beginning of current line.
• N means move forward by N - 1 lines first. N can be negative. If point reaches the beginning or end of buffer, it stops there.

;; move cursor to beginning of current line
(beginning-of-line)
;; better than (goto-char (line-beginning-position))

end-of-line

(end-of-line &optional N)

like beginning-of-line but end of line.

💡 TIP: Do not use (search-forward "\n") for moving cursor to end of line. Because you'll have special cases if the line is at the end of buffer and doesn't have a newline char. It is also slower.

💡 TIP: Do not use move-beginning-of-line or move-end-of-line. Because these are designed for interactive use.

Move Cursor to Next Line

forward-line

(forward-line &optional N)

• Move cursor to the next line, or N lines.
• N default to 1.
• If N is negative, move in the other direction.
• Cursor ends at the beginning of line.

;; move cursor to previous line, and at the beginning
(forward-line -1)

💡 TIP: Do not use next-line or previous-line. Because these are for interactive use. Their behavior changes depending on the variable line-move-visual.

Get Current Line as String

To grab current line, use:

(setq myLine
      (buffer-substring-no-properties
       (line-beginning-position)
       (line-end-position)
       ))

💡 TIP: Do not use (thing-at-point 'line). thing-at-point normally include the newline char, but if the line is at the end of buffer, then it won't. Also, thing-at-point is complex elisp code and is slower. [see ELisp: thing-at-point]

Screen Lines

If you want to move cursor across lines as defined by the screen (wrapped at edge of screen), you can use these.

• next-line
• previous-line
• line-move-visual
• line-move-visual → A variable that controls whether next-line and previous-line move by newline char or screen.

What Character Does Emacs Use for Newline

In emacs buffer, newline char is "\n", in any operating system (Mac, Linux, Microsoft Windows ). So, you can use (search-forward "\n"). However, if you are on the last line, there may not be a ending "\n".