Answer by Kamil Maciorowski for Use multiple conditions in find regex in shell

With -regextype (GNU find)

I need to use -E for extended regex.

Invoke find . -regextype help to learn available options. GNU find in my Debian supports few. Other implementations of find may or may not support -regextype though. This works with GNU find:

find . -regextype posix-extended -regex '\./(.*~$|#.*#)'

Note I have debugged and simplified the regex a little (\./.*~$|\./#.*# would also work). Other options that work for me in this particular case: posix-egrep, egrep, posix-awk, awk, gnu-awk.

Without -regextype

This command:

find . -regex '\./#.*#\|\./.*~'

where | is escaped works for me. Credits to the other answer. Proper escaping of ( and ) makes the following work as well:

find . -regex '\./\(.*~$\|#.*#\)'

without relying on extended regular expressions.

With -o

You don't have to compact the two expressions into one. If these work:

find . -regex '\./.*~'find . -regex '\./#.*#'

then you can get files matching one regex or the other this way:

find . -regex '\./.*~' -o -regex '\./#.*#'

Be warned: Why does find in Linux skip expected results when -o is used? If you want to add more tests/actions before and/or after then you don't want this:

find . -test1 -test2 -regex '\./.*~' -o -regex '\./#.*#' -test3 …

but this:

find . -test1 -test2 '(' -regex '\./.*~' -o -regex '\./#.*#'')' -test3 …