       TRAPxxx
              If defined and non-null, this function will be exe-
              cuted whenever the shell catches a  signal  SIGxxx,
              where  xxx  is  a  signal name as specified for the
              kill builtin (see below).  The signal  number  will
              be  passed  as the first parameter to the function.
              In addition, TRAPZERR is executed whenever  a  com-
              mand  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.
