module Netsys_signal:sig..end
Signal handler framework
This module defines a simple framework for setting signal handlers. When two modules want to set the handler for the same signal, the framework decides in which order the handlers are executed.
The module also defines an empty handler for Sys.sigpipe, so this
    signal is ignored by the program (and you get a
    Unix.Unix_error(EPIPE,_,_) exception instead).
If you don't like that Netsys sets the Sigpipe handler, you can undo this:
Sys.set_signal Sys.sigpipe Sys.Signal_default;;
Netsys_signal.keep_away_from Sys.sigpipe;;
    Win32: Only Sys.sigint handlers can effectively be registered. 
    Registrations for other signal types are accepted but ignored.
val register_handler : ?library:string ->
       ?priority:int ->
       ?keep_default:bool ->
       name:string -> signal:int -> callback:(int -> unit) -> unit -> unitThis function registers a handler called name for signal number
      signal. The handler function is callback. The int argument of
      the callback is the signal number.
By default, the handler is an application handler. If library is set,
      the handler is for this library. The name passed as library is the
      findlib name of the library.
By registering another handler for the same library, name, and
      signal, the old handler is overridden.
When several handlers are defined for the same signal, all handlers
      are executed that are defined for the signal (when the signal happens).
      The order of execution is given by priority. The handler functions
      are executed in ascending priority order. If the priority number is
      equal for two handlers, the order is undefined.
The priority defaults to 0 for library handlers, and to 100 for application handlers. Libraries should only use values from 0 to 99, and applications only from 100 to 199.
If all handlers for a certain signal set keep_default, then there
      will be a special action after all signal handlers have been executed.
      The special action emulates the default behavior for the signal.
      For now, there is only a simple emulation: If the signal terminates
      the process, the process is immediately exited with code 126.
      If the default behaviour is "no-op", nothing happens. We don't try
      (yet) to do better (emulate core-dumps, emulate the right process
      status) because this is difficult in the general case.
The handler definition takes place immediately.
Any exceptions occuring during the execution of a handler are caught and ignored.
val register_exclusive_handler : name:string -> signal:int -> install:(unit -> unit) -> unit -> unitAn exclusive handler for a signal is the only handler for the signal. If it is tried to register another handler when there is already an exclusive handler, the second registration fails. Also, an exclusive handler cannot be registered when there is already a normal handler for the signal. It is, however, possible to replace the registered exclusive handler by another exclusive handler for the same signal.
An exclusive handler is installed by running the install function,
      which can e.g. call Sys.set_signal to define the handler. Other
      methods (e.g. use some C wrapper) are also possible. It is assumed
      that install overrides any existing handler.
val restore_management : int -> unitrestore_management signo: Restores signal handling management for
      signo as defined by
      the handler list for this signal. Calling restore_management makes
      sense when
      the signal handler has been overridden with Sys.set_signal, but at
      some point this module is again responsible for managing the signal
      handling for this signal.
val keep_away_from : int -> unitkeep_away_from signo: This signal signo is added to the 
      "keep away list". This means that this module will never try to 
      change the signal behavior again for signo. Even restore_management
      will not restore the signal handling again. This function should only
      by called by applications wishing to do the signal handling all 
      themselves.
This function does not have any effect on the already installed
      handlers. It is nevertheless useful for applications calling
      Sys.set_signal directly to ensure that Netsys_signal will never
      again try to override the handler.
typeaction =[ `Callback of int -> unit | `Install of unit -> unit ]
`Callback is used for normal handlers, and `Install for exclusive
      handlers.
type |    | sig_number :  | 
|    | sig_library :  | 
|    | sig_priority :  | 
|    | sig_keep_default :  | 
|    | sig_name :  | 
|    | sig_action :  | 
val list : unit -> entry listReturns the list of signal handlers
val keep_away_list : unit -> int listReturns the "keep away list".
val init : unit -> unitCall this function to ensure that this module is initialized. It is also possible to call any other function. After initialization the Sigpipe handler is set.
module Debug:sig..end