Recursively: Find files / Replace string ;-)

Find files with string and write results of search to text file: ()

find . -name "*" | xargs grep -i -n "string1" >> ./../results.txt

Replace string in files with another string:

1) "/" separators:
find ./ -name "*" | xargs sed -i 's/string1/string2/'

2) "," separators:
find ./ -name "*" | xargs sed -i 's,string1(with / characters),string2(with / characters),'