"$" are different in basic regular expression and extend regular expression, see https://stackoverflow.com/questions/38114132/why-does-dollar-not-match-literal-dollar-when-extended-regex-ere-option-is-use.
https://www.gnu.org/software/findutils/manual/html_node/find_html/posix_002degrep-regular-expression-syntax.html#posix_002degrep-regular-expression-syntax
- posix-egrep’ regular expression syntax:
- The characters ‘^’ and ‘$’ always represent the beginning and end of a string respectively, except within square brackets. Within brackets, ‘^’ can be used to invert the membership of the character class being specified.
- ‘posix-basic’ regular expression syntax:
- The character ‘^’ only represents the beginning of a string when it appears:
- At the beginning of a regular expression
- After an open-group, signified by ‘\(’
- After the alternation operator ‘\|’
- The character ‘$’ only represents the end of a string when it appears:
- At the end of a regular expression
- Before a close-group, signified by ‘\)’
- Before the alternation operator ‘\|’
