TRAPxxx
          If defined and non-null, this function will be executed
          whenever  the  shell catches a signal SIGxxx, where xxx
          is a signal name as specified for the kill builtin (see
          below).   In  addition,  TRAPERR is executed whenever a
          command has a non-zero exit status, TRAPDEBUG  is  exe-
          cuted after each command, and TRAPEXIT is executed when
          the shell exits, or when the current function exits  if
          defined  inside a function.  If a function of this form
          is defined and null, the shell and processes spawned by
          it will ignore SIGxxx.