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CrtFileHdlr (3)
  • >> CrtFileHdlr (3) ( Solaris man: Библиотечные вызовы )
  • CrtFileHdlr (3) ( Разные man: Библиотечные вызовы )
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    _________________________________________________________________
    
    NAME
         Tcl_CreateFileHandler,  Tcl_DeleteFileHandler  -   associate
         procedure callbacks with files or devices (Unix only)
    
    SYNOPSIS
         #include <tcl.h>
    
         Tcl_CreateFileHandler(fd, mask, proc, clientData)             |
    
         Tcl_DeleteFileHandler(fd)                                     |
    
    ARGUMENTS
         int            fd           (in)                                   ||
                                               Unix  file  descriptor  |
                                               for an  open  file  or  |
                                               device.
    
         int            mask         (in)      Conditions under which
                                               proc should be called:
                                               OR-ed  combination  of
                                               TCL_READABLE,
                                               TCL_WRITABLE,      and
                                               TCL_EXCEPTION.  May be
                                               set  to  0   to   tem-
                                               porarily   disable   a
                                               handler.
    
         Tcl_FileProc   *proc        (in)      Procedure  to   invoke
                                               whenever  the  file or
                                               device  indicated   by
                                               file  meets the condi-
                                               tions   specified   by
                                               mask.
    
         ClientData     clientData   (in)      Arbitrary     one-word
                                               value to pass to proc.
    _________________________________________________________________
    
    
    DESCRIPTION
         Tcl_CreateFileHandler arranges for proc to be invoked in the  |
         future  whenever I/O becomes possible on a file or an excep-  |
         tional condition exists for the file.  The file is indicated  |
         by fd, and the conditions of interest are indicated by mask.
         For example, if mask is TCL_READABLE, proc  will  be  called
         when  the file is readable.  The callback to proc is made by
         Tcl_DoOneEvent, so Tcl_CreateFileHandler is only  useful  in
         programs  that  dispatch  events  through  Tcl_DoOneEvent or
         through Tcl commands such as vwait.
    
         Proc should have arguments and result that  match  the  type
         Tcl_FileProc:
              typedef void Tcl_FileProc(
                ClientData clientData,
                int mask);
         The clientData parameter to proc is a copy of the clientData
         argument  given  to  Tcl_CreateFileHandler when the callback
         was created.  Typically, clientData points to a data  struc-
         ture  containing  application-specific information about the
         file.  Mask is an  integer  mask  indicating  which  of  the
         requested  conditions actually exists for the file;  it will
         contain a subset  of  the  bits  in  the  mask  argument  to
         Tcl_CreateFileHandler.
    
         There may exist only one handler for a given file at a given
         time.   If  Tcl_CreateFileHandler  is  called when a handler
         already exists for fd, then the new  callback  replaces  the
         information that was previously recorded.
    
         Tcl_DeleteFileHandler may  be  called  to  delete  the  file
         handler  for fd;  if no handler exists for the file given by
         fd then the procedure has no effect.
    
         The purpose of file handlers is to enable an application  to
         respond  to  events  while waiting for files to become ready
         for I/O.  For this to work correctly,  the  application  may
         need  to  use  non-blocking  I/O operations on the files for
         which handlers are declared.  Otherwise the application  may
         block if it reads or writes too much data; while waiting for
         the I/O to complete the application won't be able to service
         other events. Use Tcl_SetChannelOption with -blocking to set
         the channel into blocking or nonblocking mode as required.
    
         Note that these interfaces are only supported  by  the  Unix  |
         implementation of the Tcl notifier.
    
    
    KEYWORDS
         callback, file, handler
    
    
    
    


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