Tcl_CreateObjCommand,   Tcl_DeleteCommand,  Tcl_DeleteCommandFromToken,
       Tcl_GetCommandInfo,  Tcl_GetCommandInfoFromToken,   Tcl_SetCommandInfo,
       Tcl_SetCommandInfoFromToken,   Tcl_GetCommandName,  Tcl_GetCommandFull-
       Name, Tcl_GetCommandFromObj - 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)

       int                                                                     |
       Tcl_GetCommandInfoFromToken(token, infoPtr)                             |

       int                                                                     |
       Tcl_SetCommandInfoFromToken(token, infoPtr)                             |

       CONST char *                                                            |
       Tcl_GetCommandName(interp, token)

       Tcl_GetCommandFullName(interp, token, objPtr)

       Tcl_GetCommandFromObj(interp, objPtr)


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

       char             *cmd-                                                  |
       Name      (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_Obj          *objPtr       (in)      Object containing the name  of
                                                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_EvalObjEx) the Tcl interpreter will call proc
       to process the command.

       Tcl_CreateObjCommand deletes any existing command name already  associ-
       ated with the interpreter (however see below for an exception where the
       existing command is not deleted).  It returns a token that may be  used
       to  refer to the command in subsequent calls to Tcl_GetCommandName.  If
       name contains 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_GetIntFromObj 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] |

       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_EvalObjEx 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.

       Ordinarily,  Tcl_CreateObjCommand  deletes  any  existing  command name
       already associated with the interpreter.  However, if the existing com-
       mand was created by a previous call to Tcl_CreateCommand, Tcl_CreateOb-
       jCommand does not delete the command but instead arranges for  the  Tcl
       interpreter  to  call  the  Tcl_ObjCmdProc proc in the future.  The old
       string-based Tcl_CmdProc associated with the command  is  retained  and
       its  address  can  be  obtained by subsequent Tcl_GetCommandInfo calls.
       This is done for backwards compatibility.

       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_GetCommandInfoFromToken is identical to  Tcl_GetCommandInfo  except
       that  it  uses  a  command  token returned from Tcl_CreateObjCommand in
       place of the command name.  If the token parameter is NULL, it  returns
       0;  otherwise,  it  returns  1 and fills in the structure designated by

       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.

       Tcl_SetCommandInfoFromToken is identical to  Tcl_SetCommandInfo  except
       that  it  takes  a  command  token  as returned by Tcl_CreateObjCommand
       instead of the command name.   If  the  token  parameter  is  NULL,  it
       returns 0.  Otherwise, it copies the information from *infoPtr to Tcl's
       internal structure for the command and returns 1.

       Note that Tcl_SetCommandInfo and Tcl_SetCommandInfoFromToken both allow
       the ClientData for a command's deletion procedure to be given a differ-
       ent value than the ClientData for its command procedure.

       Note that neither  Tcl_SetCommandInfo  nor  Tcl_SetCommandInfoFromToken
       will  change  a  command's  namespace.  Use Tcl_Eval to call the rename
       command to do that.

       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_GetCommandFullName produces the fully-qualified name of  a  command
       from  a  command token.  The name, including all namespace prefixes, is
       appended to the object specified by objPtr.

       Tcl_GetCommandFromObj returns a token for the command specified by  the
       name  in  a Tcl_Obj.  The command name is resolved relative to the cur-
       rent namespace.  Returns NULL if the command is not found.


       Tcl_CreateCommand, Tcl_ResetResult, Tcl_SetObjResult


       bind, command, create, delete, namespace, object

Tcl                                   8.0              Tcl_CreateObjCommand(3)

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