— Command: delete-horizontal-space &optional backward-only

This function deletes all spaces and tabs around point. It returns nil.

If backward-only is non-nil, the function deletes spaces and tabs before point, but not after point.

In the following examples, we call delete-horizontal-space four times, once on each line, with point between the second and third characters on the line each time.

          ---------- Buffer: foo ----------
          I -!-thought
          I -!-     thought
          We-!- thought
          Yo-!-u thought
          ---------- Buffer: foo ----------
          
          (delete-horizontal-space)   ; Four times.
               ⇒ nil
          
          ---------- Buffer: foo ----------
          Ithought
          Ithought
          Wethought
          You thought
          ---------- Buffer: foo ----------

— Command: delete-indentation &optional join-following-p

This function joins the line point is on to the previous line, deleting any whitespace at the join and in some cases replacing it with one space. If join-following-p is non-nil, delete-indentation joins this line to the following line instead. The function returns nil.

If there is a fill prefix, and the second of the lines being joined starts with the prefix, then delete-indentation deletes the fill prefix before joining the lines. See Margins.

In the example below, point is located on the line starting ‘events’, and it makes no difference if there are trailing spaces in the preceding line.

          ---------- Buffer: foo ----------
          When in the course of human
          -!-    events, it becomes necessary
          ---------- Buffer: foo ----------
          
          (delete-indentation)
               ⇒ nil
          
          ---------- Buffer: foo ----------
          When in the course of human-!- events, it becomes necessary
          ---------- Buffer: foo ----------

After the lines are joined, the function fixup-whitespace is responsible for deciding whether to leave a space at the junction.

— Command: fixup-whitespace

This function replaces all the horizontal whitespace surrounding point with either one space or no space, according to the context. It returns nil.

At the beginning or end of a line, the appropriate amount of space is none. Before a character with close parenthesis syntax, or after a character with open parenthesis or expression-prefix syntax, no space is also appropriate. Otherwise, one space is appropriate. See Syntax Class Table.

In the example below, fixup-whitespace is called the first time with point before the word ‘spaces’ in the first line. For the second invocation, point is directly after the ‘(’.

          ---------- Buffer: foo ----------
          This has too many     -!-spaces
          This has too many spaces at the start of (-!-   this list)
          ---------- Buffer: foo ----------
          
          (fixup-whitespace)
               ⇒ nil
          (fixup-whitespace)
               ⇒ nil
          
          ---------- Buffer: foo ----------
          This has too many spaces
          This has too many spaces at the start of (this list)
          ---------- Buffer: foo ----------

— Command: just-one-space &optional n

This command replaces any spaces and tabs around point with a single space, or n spaces if n is specified. It returns nil.

— Command: delete-blank-lines

This function deletes blank lines surrounding point. If point is on a blank line with one or more blank lines before or after it, then all but one of them are deleted. If point is on an isolated blank line, then it is deleted. If point is on a nonblank line, the command deletes all blank lines immediately following it.

A blank line is defined as a line containing only tabs and spaces.

delete-blank-lines returns nil.

— Command: delete-trailing-whitespace &optional start end

Delete trailing whitespace in the region defined by start and end.

This command deletes whitespace characters after the last non-whitespace character in each line in the region.

If this command acts on the entire buffer (i.e., if called interactively with the mark inactive, or called from Lisp with end nil), it also deletes all trailing lines at the end of the buffer if the variable delete-trailing-lines is non-nil.