peek-char

(peek-char &optional peek-type stream eof-error-p eof-value)

Returns the next character of stream (default: standard input) without consuming it, so the following read-char returns the same character. peek-type selects what to skip first: nil (the default) skips nothing, t skips whitespace, and a character skips input up to that character. In every case the character that is returned is left in the stream. At end of input it signals an end-of-file condition unless eof-error-p is nil, in which case it returns eof-value (default nil).