ACC SHELL

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
       defaults, or, if no sig args are present, all traps are reset.

       If  arg  is  an  empty  string,  then  the specified signals are
       ignored 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
       associated 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.

       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
       another.