Elisp: Functions on Line

Get Position of Beginning of Line

pos-bol

(pos-bol &optional N)

return beginning of line position.

new in Emacs 29 (date 2023)

pos-eol

(pos-eol &optional N)

return end of line position.

new in Emacs 29 (date 2023)

line-beginning-position

(line-beginning-position &optional N)

return beginning of line position, but stop at fields.

(fields are text regions that have Text Property of field. Used for things such as minibuffer prompt text.)

If N is 1, it means current line. 2 means next line. -1 means last line, etc.

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 end of line position, but stop at fields.

Move Cursor to Beginning of Line

beginning-of-line

(beginning-of-line &optional N)

Move point to beginning of current line, but stop at fields. To ignore field, use (forward-line 0)

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, Previous 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 the beginning of previous line
(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.

Check If Cursor is at Beginning of Line, End of Line

bolp

Return t if point is at the beginning of a line.

eolp

Return t if point is at the end of a line.

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 ).