How do you pronounce the << operator

In the context of iostreams, writers often will refer to << and >> as the “put-to” or "stream insertion" and “get-from” or "stream extraction" operators, respectively* .

If you are using << for output in C++ programming then I would just call it "put-to".

(Otherwise, that would also be used as the bitwise left shift in binary operations, but I doubt that is what you meant)

Just found following in TC++PL 3rd Edition page 25, for your reference.

The << operator (“put to”) is used as an output operator; cout is the standard output stream. The >> operator (“get from”) is used as an input operator; cin is the standard input stream. The type of the righthand operand of >> determines what input is accepted and is the target of the input operation. The \n character at the end of the output string represents a newline.