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Tcl_CreateObjCommand(3)	    Tcl Library Procedures     Tcl_CreateObjCommand(3)


       Tcl_CreateObjCommand,   Tcl_DeleteCommand,  Tcl_DeleteCommandFromToken,
       Tcl_GetCommandInfo, Tcl_SetCommandInfo, Tcl_GetCommandName -  implement
       new commands in C

       #include <tcl.h>

       Tcl_CreateObjCommand(interp, cmdName, proc, clientData, deleteProc)

       Tcl_DeleteCommand(interp, cmdName)

       Tcl_DeleteCommandFromToken(interp, token)

       Tcl_GetCommandInfo(interp, cmdName, infoPtr)

       Tcl_SetCommandInfo(interp, cmdName, infoPtr)

       char *
       Tcl_GetCommandName(interp, token)

       Tcl_Interp	*interp	      (in)	Interpreter in which to create
						a new command or that contains
						a command.

       char		*cmdName      (in)	Name of command.

       Tcl_ObjCmdProc	*proc	      (in)	Implementation of the new com‐
						mand:  proc  will  be	called
						whenever cmdName is invoked as
						a command.

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

       Tcl_CmdDeleteProc	      *deleteProc(in)
						Procedure  to call before cmd‐
						Name  is  deleted   from   the
						interpreter;  allows  for com‐
						mand-specific	cleanup.    If
						NULL,  then  no	 procedure  is
						called before the  command  is

       Tcl_Command	token	      (in)	Token for command, returned by
						previous call to Tcl_CreateOb‐
						jCommand.   The	 command  must
						not have been deleted.

       Tcl_CmdInfo	*infoPtr      (in/out)	Pointer to structure  contain‐
						ing  various information about
						a Tcl command.

       Tcl_CreateObjCommand defines a new command in interp and associates  it
       with procedure proc such that whenever name is invoked as a Tcl command
       (e.g., via a call to Tcl_EvalObj) the Tcl interpreter will call proc to
       process the command.

       Tcl_CreateObjCommand  will  delete  any command name already associated
       with the interpreter.  It returns a token that may be used to refer  to
       the  command  in	 subsequent calls to Tcl_GetCommandName.  If name con‐
       tains any :: namespace qualifiers, then the command  is	added  to  the
       specified  namespace;  otherwise	 the  command  is  added to the global
       namespace.  If Tcl_CreateObjCommand is called for an  interpreter  that
       is  in the process of being deleted, then it does not create a new com‐
       mand and it returns NULL.  proc should have arguments and  result  that
       match the type Tcl_ObjCmdProc:
	      typedef int Tcl_ObjCmdProc(
		ClientData clientData,
		Tcl_Interp *interp,
		int objc,
		Tcl_Obj *CONST objv[]);					       │
       When  proc  is  invoked,	 the  clientData and interp parameters will be │
       copies of the clientData and interp arguments given  to	Tcl_CreateObj‐ │
       Command.	  Typically, clientData points to an application-specific data │
       structure that describes what to	 do  when  the	command	 procedure  is │
       invoked. Objc and objv describe the arguments to the command, objc giv‐ │
       ing the number of argument objects (including  the  command  name)  and │
       objv  giving  the values of the arguments.  The objv array will contain │
       objc values, pointing to the argument objects.  Unlike argv[argv]  used │
       in a string-based command procedure, objv[objc] will not contain NULL.  │

       Additionally,  when proc is invoked, it must not modify the contents of │
       the objv array by assigning new pointer values to any  element  of  the │
       array  (for  example, objv[2] = NULL) because this will cause memory to │
       be lost and the runtime stack to be corrupted.  The CONST in the decla‐ │
       ration  of  objv will cause ANSI-compliant compilers to report any such │
       attempted assignment as an error.  However, it is acceptable to	modify │
       the  internal  representation  of  any individual object argument.  For │
       instance, the user may call Tcl_GetIntFromObject on objv[2]  to	obtain │
       the  integer  representation  of	 that object; that call may change the │
       type of the object that objv[2] points at, but will  not	 change	 where │
       objv[2] points.

       proc  must  return  an  integer	code that is either TCL_OK, TCL_ERROR,
       TCL_RETURN, TCL_BREAK, or TCL_CONTINUE.	See the Tcl overview man  page
       for  details  on what these codes mean.	Most normal commands will only
       return TCL_OK or TCL_ERROR.  In addition, if proc  needs	 to  return  a
       non-empty result, it can call Tcl_SetObjResult to set the interpreter's
       result.	In the case of a TCL_OK return code this gives the  result  of
       the  command, and in the case of TCL_ERROR this gives an error message.
       Before invoking a command  procedure,  Tcl_EvalObj  sets	 interpreter's
       result  to  point  to an object representing an empty string, so simple
       commands can return an empty result by doing nothing at all.

       The contents of the objv array belong to Tcl and are not guaranteed  to
       persist once proc returns: proc should not modify them.	Call Tcl_SetO‐
       bjResult if you want to return something from the objv array.

       DeleteProc will be invoked when (if) name is deleted.  This  can	 occur
       through	a  call	 to  Tcl_DeleteCommand, Tcl_DeleteCommandFromToken, or
       Tcl_DeleteInterp, or by replacing name in another call to Tcl_CreateOb‐
       jCommand.   DeleteProc  is  invoked  before the command is deleted, and
       gives the application an opportunity to release any structures  associ‐
       ated  with  the	command.   DeleteProc should have arguments and result
       that match the type Tcl_CmdDeleteProc:
	      typedef void Tcl_CmdDeleteProc(ClientData clientData);
       The clientData argument will be the same	 as  the  clientData  argument
       passed to Tcl_CreateObjCommand.

       Tcl_DeleteCommand  deletes  a command from a command interpreter.  Once
       the call completes, attempts to invoke cmdName in interp will result in
       errors.	  If   cmdName	isn't  bound  as  a  command  in  interp  then
       Tcl_DeleteCommand does nothing and returns -1;  otherwise it returns 0.
       There  are no restrictions on cmdName:  it may refer to a built-in com‐
       mand, an application-specific command, or a  Tcl	 procedure.   If  name
       contains	 any  :: namespace qualifiers, the command is deleted from the
       specified namespace.

       Given a token returned by Tcl_CreateObjCommand,	Tcl_DeleteCommandFrom‐
       Token deletes the command from a command interpreter.  It will delete a
       command even if that command has been  renamed.	 Once  the  call  com‐
       pletes, attempts to invoke the command in interp will result in errors.
       If the command corresponding to token has  already  been	 deleted  from
       interp then Tcl_DeleteCommand does nothing and returns -1; otherwise it
       returns 0.

       Tcl_GetCommandInfo checks to see whether its cmdName argument exists as
       a  command  in  interp.	cmdName may include :: namespace qualifiers to
       identify a command in a particular namespace.  If the  command  is  not
       found,  then  it	 returns 0.  Otherwise it places information about the
       command in the Tcl_CmdInfo structure pointed to by infoPtr and  returns
       1.  A Tcl_CmdInfo structure has the following fields:
	      typedef struct Tcl_CmdInfo {
		  int isNativeObjectProc;
		  Tcl_ObjCmdProc *objProc;
		  ClientData objClientData;
		  Tcl_CmdProc *proc;
		  ClientData clientData;
		  Tcl_CmdDeleteProc *deleteProc;
		  ClientData deleteData;
		  Tcl_Namespace *namespacePtr;
	      } Tcl_CmdInfo;
       The  isNativeObjectProc	field  has the value 1 if Tcl_CreateObjCommand
       was called to register the command; it is 0 if  only  Tcl_CreateCommand
       was  called.   It allows a program to determine whether it is faster to
       call objProc or proc: objProc is normally faster if  isNativeObjectProc
       has  the	 value	1.  The fields objProc and objClientData have the same
       meaning as the proc and clientData arguments  to	 Tcl_CreateObjCommand;
       they hold information about the object-based command procedure that the
       Tcl interpreter calls to implement the command.	The  fields  proc  and
       clientData  hold	 information  about the string-based command procedure
       that implements the command.  If Tcl_CreateCommand was called for  this
       command,	 this is the procedure passed to it; otherwise, this is a com‐
       patibility procedure registered	by  Tcl_CreateObjCommand  that	simply
       calls  the command's object-based procedure after converting its string
       arguments to Tcl objects.  The field deleteData is the ClientData value
       to  pass	 to deleteProc;	 it is normally the same as clientData but may
       be set independently using the Tcl_SetCommandInfo procedure.  The field
       namespacePtr  holds  a  pointer	to the Tcl_Namespace that contains the

       Tcl_SetCommandInfo is used to modify the procedures and ClientData val‐
       ues  associated	with a command.	 Its cmdName argument is the name of a
       command in interp.  cmdName may	include	 ::  namespace	qualifiers  to
       identify a command in a particular namespace.  If this command does not
       exist then Tcl_SetCommandInfo returns  0.   Otherwise,  it  copies  the
       information  from  *infoPtr to Tcl's internal structure for the command
       and returns 1.  Note that this procedure allows the  ClientData	for  a
       command's  deletion  procedure  to  be given a different value than the
       ClientData for its command procedure.  Note  that  Tcl_SetCmdInfo  will
       not  change a command's namespace; you must use Tcl_RenameCommand to do

       Tcl_GetCommandName provides a mechanism for tracking commands that have
       been  renamed.  Given a token returned by Tcl_CreateObjCommand when the
       command was created, Tcl_GetCommandName returns the string name of  the
       command.	  If  the  command has been renamed since it was created, then
       Tcl_GetCommandName returns  the	current	 name.	 This  name  does  not
       include	any  ::	 namespace  qualifiers.	  The command corresponding to
       token must not have been deleted.  The string returned  by  Tcl_GetCom‐
       mandName	 is  in	 dynamic memory owned by Tcl and is only guaranteed to
       retain its value as long as  the	 command  isn't	 deleted  or  renamed;
       callers should copy the string if they need to keep it for a long time.

       Tcl_CreateCommand, Tcl_ResetResult, Tcl_SetObjResult

       bind, command, create, delete, namespace, object

Tcl				      8.0	       Tcl_CreateObjCommand(3)

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