regex expression or in batch

Question

How can I write a regex expression with OR in batch. I have a file and I want to find "aa" or "bb". The file contains these lines:

aa
bb
cc

This is the command I have tryed:

findstr /I /R /C:"aa\|bb" temp.txt

and

findstr /I /R /C:"aa|bb" temp.txt

Can anyone help me with the OR syntax in batch for writing regular expressions.

Thanks.

Answer 1

Quoted from the doc:

FINDSTR does not support alternation with the pipe character (|) multiple Regular Expressions can be separated with spaces, just the same as separating multiple words (assuming you have not specified a literal search with /C) but this may not be useful if the regex itself contains spaces.

Reference: http://ss64.com/nt/findstr.html