READ

(READ [<stream> [<eof-error-p> [<eof-value>]]])

Reads an S-expression from the given <stream>, or from the standard input
if no arguments are given.

<eof-error-p> (true by default) determines whether end-of-file should be
considered error. Specify NIL if you think it is a correct situation. If
you do so and the function encounters the end of file, it returns either a
special unique EOF value, or <eof-value>, if it is given.

NOTE: this function doesn't protect your program from syntax errors in the
incoming stream, and therefore should be considered dangerous and
deprecated. Consider using SAFEREAD instead.