Exclude multiple lines from in Bash (Version: 3.2.48) - regex

Question

The idea is to calculate SHA256 hashes for all files in a directory (including all subdirectories), but exclude some files specified in another text file.
The problem is if I specify the following files (see below the code) to exclude, only one of them is excluded, not both.
Here is my code:
while read line
do
if [ $line_count -eq 0 ]
then
exclude_files=".*/$line$"
else
exclude_files="${exclude_files}\|.*/$line$"
fi
line_count=$(( $line_count + 1 ))
done < exclude-files.txt
find . -type f -print0 | xargs -0 shasum -a 256 | grep -v -P "${exclude_files}" > ~/out.txt
Contents of the file exclude-files.txt:
Icon\\r
.DS_Store
--- empty line ---
The file Icon\r is a special file for changing a folder's icon, its name contains a CR. (I'm on Mac OS X 10.7.4)

Answer 1

This is because in your variable \ is recognized as escape symbol for |:
exclude_files="${exclude_files}\|.*/$line$"
you need to add anothers \ to escape \ to get it work:
exclude_files="${exclude_files}\\|.*/$line$"
Also you're using -P option in grep. In this case you don't need to escape |. Therefore you use it without backslash at all.
You should to chose which way you will use: escape or -P. Both together they won't work.

Answer 2

grep would not be safe if filenames contain character with a special meaning, maybe this can help
cmd=(find . -type f \( )
while read line;do cmd=("${cmd[#]}" \! -name "$line" -a);done < exclude-files.txt
cmd[${#cmd[*]}-1]=\)
echo "${cmd[#]}" | cat -v
"${cmd[#]}" -print0 | xargs -0 shasum -a 256