Tcl_Main man page on QNX

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Tcl_Main(3)		    Tcl Library Procedures		   Tcl_Main(3)


       Tcl_Main,  Tcl_SetMainLoop - main program and event loop definition for
       Tcl-based applications

       #include <tcl.h>

       Tcl_Main(argc, argv, appInitProc)


       int		 argc		(in)	  Number of elements in argv.

       char		 *argv[]	(in)	  Array of strings  containing
						  command-line arguments.

       Tcl_AppInitProc	 *appInitProc	(in)	  Address  of  an application-
						  specific initialization pro‐
						  cedure.   The value for this
						  argument     is      usually

       Tcl_MainLoopProc	 *mainLoopProc	(in)	  Address  of  an application-
						  specific event  loop	proce‐

       Tcl_Main	 can  serve  as	 the main program for Tcl-based shell applica‐
       tions.  A ``shell application'' is a program like tclsh	or  wish  that
       supports	 both  interactive  interpretation  of Tcl and evaluation of a
       script contained in a file given as a command line argument.   Tcl_Main
       is  offered  as	a  convenience to developers of shell applications, so
       they do not have to reproduce all of the code for proper initialization
       of  the	Tcl  library and interactive shell operation.  Other styles of
       embedding Tcl in an application are not supported by  Tcl_Main.	 Those
       must  be	 achieved  by calling lower level functions in the Tcl library

       The Tcl_Main function has been offered by the Tcl library since release
       Tcl  7.4.   In  older releases of Tcl, the Tcl library itself defined a
       function main, but that lacks flexibility of embedding style and having
       a  function  main  in  a library (particularly a shared library) causes
       problems on many systems.  Having main in the Tcl  library  would  also
       make  it	 hard to use Tcl in C++ programs, since C++ programs must have
       special C++ main functions.

       Normally each shell application contains a  small  main	function  that
       does  nothing  but invoke Tcl_Main.  Tcl_Main then does all the work of
       creating and running a tclsh-like application.

       Tcl_Main is not provided by the public interface of Tcl's stub library.
       Programs	 that  call  Tcl_Main  must be linked against the standard Tcl
       library.	 Extensions (stub-enabled or not) are  not  intended  to  call

       Tcl_Main is not thread-safe.  It should only be called by a single mas‐
       ter thread of a multi-threaded application.  This restriction is not  a
       problem with normal use described above.

       Tcl_Main	 and therefore all applications based upon it, like tclsh, use
       Tcl_GetStdChannel to initialize the standard channels to their  default
       values. See Tcl_StandardChannels for more information.

       Tcl_Main	 supports  two	modes of operation, depending on the values of
       argc and argv.  If argv[1] exists and does not begin with the character
       -,  it  is  taken to be the name of a file containing a startup script,
       which Tcl_Main will attempt  to	evaluate.   Otherwise,	Tcl_Main  will
       enter an interactive mode.

       In  either mode, Tcl_Main will define in its master interpreter the Tcl
       variables argc, argv, argv0, and tcl_interactive, as described  in  the
       documentation for tclsh.

       When  it	 has  finished its own initialization, but before it processes
       commands, Tcl_Main calls the procedure given by the  appInitProc	 argu‐
       ment.   This  procedure provides a ``hook'' for the application to per‐
       form its own initialization of the  interpreter	created	 by  Tcl_Main,
       such  as	 defining  application-specific	 commands.  The procedure must
       have an interface that matches the type Tcl_AppInitProc:
	      typedef int Tcl_AppInitProc(Tcl_Interp *interp);

       AppInitProc is almost always a pointer to Tcl_AppInit; for more details
       on this procedure, see the documentation for Tcl_AppInit.

       When the appInitProc is finished, Tcl_Main enters one of its two modes.
       If a startup script has been provided, Tcl_Main	attempts  to  evaluate
       it.   Otherwise,	 interactive mode begins with examination of the vari‐
       able tcl_rcFileName in the master interpreter.  If that variable exists
       and  holds  the	name of a readable file, the contents of that file are
       evaluated in  the  master  interpreter.	 Then  interactive  operations
       begin, with prompts and command evaluation results written to the stan‐
       dard output channel, and commands read from the standard input  channel
       and then evaluated.  The prompts written to the standard output channel
       may be  customized  by  defining	 the  Tcl  variables  tcl_prompt1  and
       tcl_prompt2  as	described in the documentation for tclsh.  The prompts
       and command evaluation results are written to the standard output chan‐
       nel  only if the Tcl variable tcl_interactive in the master interpreter
       holds a non-zero integer value.

       Tcl_SetMainLoop allows setting an event loop procedure to be run.  This │
       allows,	for  example,  Tk  to  be dynamically loaded and set its event │
       loop.  The event loop will run following the startup  script.   If  you │
       are in interactive mode, setting the main loop procedure will cause the │
       prompt to become fileevent based and then the loop procedure is called. │
       When the loop procedure returns in interactive mode, interactive opera‐ │
       tion will continue.  The main loop procedure  must  have	 an  interface │
       that matches the type Tcl_MainLoopProc:				       │
	      typedef void Tcl_MainLoopProc(void);			       │

       Tcl_Main	 does  not  return.  Normally a program based on Tcl_Main will
       terminate when the exit command is evaluated.  In interactive mode,  if
       an  EOF	or channel error is encountered on the standard input channel,
       then Tcl_Main itself will evaluate the exit command after the main loop
       procedure  (if  any)  returns.  In non-interactive mode, after Tcl_Main
       evaluates the startup script, and the  main  loop  procedure  (if  any)
       returns, Tcl_Main will also evaluate the exit command.

       tclsh(1),	 Tcl_GetStdChannel(3),	      Tcl_StandardChannels(3),
       Tcl_AppInit(3), exit(n)

       application-specific initialization, command-line arguments, main  pro‐

Tcl				      8.4			   Tcl_Main(3)
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