Tcl_DeleteFileHandler man page on QNX

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Tcl_CreateFileHandler(3)    Tcl Library Procedures    Tcl_CreateFileHandler(3)


       Tcl_CreateFileHandler,	Tcl_DeleteFileHandler  -  associate  procedure
       callbacks with files or devices (Unix only)

       #include <tcl.h>

       Tcl_CreateFileHandler(fd, mask, proc, clientData)		       │

       int	      fd	   (in)					       │
					     Unix file descriptor for an  open │
					     file or device.

       int	      mask	   (in)	     Conditions	  under	  which	  proc
					     should be called: OR-ed  combina‐
					     tion	of	 TCL_READABLE,
					     May  be  set  to 0 to temporarily
					     disable a handler.

       Tcl_FileProc   *proc	   (in)	     Procedure to invoke whenever  the
					     file  or device indicated by file
					     meets the conditions specified by

       ClientData     clientData   (in)	     Arbitrary	one-word value to pass
					     to proc.

       Tcl_CreateFileHandler arranges for proc to be  invoked  in  the	future │
       whenever	 I/O  becomes  possible	 on a file or an exceptional 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_READ‐
       ABLE, 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.	 Typi‐
       cally,  clientData  points  to a data structure containing application-
       specific information about the file.  Mask is an integer mask  indicat‐
       ing which of the requested conditions actually exists for the file;  it
       will contain a subset of the bits in the mask argument  to  Tcl_Create‐

       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

       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

       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 opera‐
       tions  on  the  files  for  which handlers are declared.	 Otherwise the
       application may block if it reads or writes too much data; while	 wait‐
       ing  for	 the  I/O to complete the application won't be able to service
       other events. Use Tcl_SetChannelOption with -blocking to set the	 chan‐
       nel into blocking or nonblocking mode as required.

       Note  that  these interfaces are only supported by the Unix implementa‐ │
       tion of the Tcl notifier.

       callback, file, handler

Tcl				      8.0	      Tcl_CreateFileHandler(3)
                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
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