Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)



     Tcl_CreateObjCommand,                     Tcl_DeleteCommand,
     Tcl_DeleteCommandFromToken,              Tcl_GetCommandInfo,
     Tcl_GetCommandInfoFromToken,             Tcl_SetCommandInfo,
     Tcl_SetCommandInfoFromToken,             Tcl_GetCommandName,
     Tcl_GetCommandFullName,  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)

     Tcl_GetCommandInfoFromToken(token, infoPtr)

     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

     char *cmdName (in)                          Name of command.

Tcl                     Last change: 8.0                        1

Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)

     Tcl_ObjCmdProc *proc (in)                   Implementation
                                                 of  the new com-
                                                 mand: proc  will
                                                 be  called when-
                                                 ever cmdName  is
                                                 invoked   as   a

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

     Tcl_CmdDeleteProc *deleteProc (in)          Procedure     to
                                                 call      before
                                                 cmdName       is
                                                 deleted from the
                                                 allows       for
                                                 cleanup.      If
                                                 NULL,  then   no
                                                 procedure     is
                                                 called    before
                                                 the  command  is

     Tcl_Command token (in)                      Token  for  com-
                                                 mand,   returned
                                                 by previous call
                                                 The command must
                                                 not  have   been

     Tcl_CmdInfo *infoPtr (in/out)               Pointer       to
                                                 structure   con-
                                                 taining  various
                                                 about a Tcl com-

     Tcl_Obj *objPtr (in)                        Object  contain-
                                                 ing  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)

Tcl                     Last change: 8.0                        2

Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)

     the Tcl interpreter will call proc to process the command.

     Tcl_CreateObjCommand  deletes  any  existing  command   name
     already  associated  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 command and it returns NULL.  proc
     should  have  arguments  and  result  that  match  the  type
          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_CreateObjCommand.  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 giving 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 declaration 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 represen-
     tation 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 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

Tcl                     Last change: 8.0                        3

Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)

     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_SetObjResult if you  want  to  return
     something from the objv array.

     Ordinarily, Tcl_CreateObjCommand deletes any  existing  com-
     mand name already associated with the interpreter.  However,
     if the existing command was created by a  previous  call  to
     Tcl_CreateCommand,  Tcl_CreateObjCommand 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_CreateObjCommand.
     DeleteProc is invoked before the  command  is  deleted,  and
     gives  the  application an opportunity to release any struc-
     tures associated 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  inter-
     preter.  Once the call completes, attempts to invoke cmdName
     in interp will result in errors.  If cmdName is not bound as
     a  command in interp then Tcl_DeleteCommand does nothing and
     returns -1;  otherwise it returns 0.  There are no  restric-
     tions  on  cmdName:   it may refer to a built-in command, 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_DeleteCommandFromToken  deletes  the command from a com-
     mand interpreter.  It will delete a  command  even  if  that
     command has been renamed.  Once the call completes, 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                     Last change: 8.0                        4

Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)

     Tcl_GetCommandInfo checks to see whether its  cmdName  argu-
     ment  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 pro-
     gram  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 client-
     Data hold information about the  string-based  command  pro-
     cedure  that  implements  the command.  If Tcl_CreateCommand
     was called for this command, this is the procedure passed to
     it;  otherwise, this is a compatibility 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 command.

     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; other-
     wise, it returns 1 and fills in the structure designated  by

     Tcl_SetCommandInfo is used  to  modify  the  procedures  and
     ClientData  values  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

Tcl                     Last change: 8.0                        5

Tcl_CreateObjCommand(3Tcl Library ProcedureTcl_CreateObjCommand(3)

     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.  Other-
     wise, 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 different 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

     Tcl_GetCommandName provides a mechanism  for  tracking  com-
     mands  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_GetCommandName is in  dynamic  memory
     owned  by  Tcl and is only guaranteed to retain its value as
     long as the command is  not  deleted  or  renamed;   callers
     should  copy  the  string if they need to keep it for a long

     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

     Tcl_GetCommandFromObj returns a token for the command speci-
     fied by the name in a Tcl_Obj.  The command name is resolved
     relative to the current namespace.  Returns NULL if the com-
     mand is not found.


     Tcl_CreateCommand, Tcl_ResetResult, Tcl_SetObjResult


     bind, command, create, delete, namespace, object

Tcl                     Last change: 8.0                        6

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