14.3.2 The Match-any-character Operator (.)

This operator matches any single printing or nonprinting character except it won't match a:

newline

if the syntax bit RE_DOT_NEWLINE isn't set.

null

if the syntax bit RE_DOT_NOT_NULL is set.

The ‘.’ (period) character represents this operator. For example, ‘a.b’ matches any three-character string beginning with ‘a’ and ending with ‘b’.