trap [ arg ] [ sig ... ]
       arg is a series of commands (usually quoted to protect  it  from
       immediate  evaluation by the shell) to be read and executed when
       the shell receives any of the signals specified by one  or  more
       sig  args.  Each sig can be given as a number, or as the name of
       a signal either with or without the string SIG in front (e.g. 1,
       HUP, and SIGHUP are all the same signal).

       If arg is `-', then the specified signals are reset to their de-
       faults, or, if no sig args are present, all traps are reset.

       If arg is an empty string, then the specified  signals  are  ig-
       nored by the shell (and by the commands it invokes).

       If  arg  is  omitted but one or more sig args are provided (i.e.
       the first argument is a valid signal number or name), the effect
       is the same as if arg had been specified as `-'.

       The trap command with no arguments prints a list of commands as-
       sociated with each signal.

       If sig is ZERR then arg will be executed after each command with
       a nonzero exit status.  ERR is an alias for ZERR on systems that
       have no SIGERR signal (this is the usual case).

       If sig is DEBUG then arg will be executed before each command if
       the  option  DEBUG_BEFORE_CMD is set (as it is by default), else
       after each command.  Here, a `command' is what is described as a
       `sublist'  in the shell grammar, see the section SIMPLE COMMANDS
       & PIPELINES in zshmisc(1).  If DEBUG_BEFORE_CMD is  set  various
       additional  features  are  available.   First, it is possible to
       skip the next command by setting the option  ERR_EXIT;  see  the
       description  of the ERR_EXIT option in zshoptions(1).  Also, the
       shell parameter ZSH_DEBUG_CMD is set to the string corresponding
       to  the  command  to  be executed following the trap.  Note that
       this string is reconstructed from the internal  format  and  may
       not be formatted the same way as the original text.  The parame-
       ter is unset after the trap is executed.

       If sig is 0 or EXIT and the trap statement  is  executed  inside
       the  body  of a function, then the command arg is executed after
       the function completes.  The value of $? at the start of  execu-
       tion is the exit status of the shell or the return status of the
       function exiting.  If sig is 0 or EXIT and the trap statement is
       not executed inside the body of a function, then the command arg
       is executed when the shell terminates; the trap runs before  any
       zshexit hook functions.

       ZERR, DEBUG, and EXIT traps are not executed inside other traps.
       ZERR and DEBUG traps are  kept  within  subshells,  while  other
       traps are reset.

       Note  that traps defined with the trap builtin are slightly dif-
       ferent from those defined as `TRAPNAL () { ... }', as the latter
       have  their  own function environment (line numbers, local vari-
       ables, etc.) while the former use the environment of the command
       in which they were called.  For example,

              trap 'print $LINENO' DEBUG

       will  print  the  line number of a command executed after it has
       run, while

              TRAPDEBUG() { print $LINENO; }

       will always print the number zero.

       Alternative signal names are allowed  as  described  under  kill
       above.   Defining a trap under either name causes any trap under
       an alternative name to be removed.  However, it  is  recommended
       that  for consistency users stick exclusively to one name or an-
       other.