1Tcl_CreateObjCommand(3)     Tcl Library Procedures     Tcl_CreateObjCommand(3)
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5______________________________________________________________________________
6

NAME

8       Tcl_CreateObjCommand,   Tcl_DeleteCommand,  Tcl_DeleteCommandFromToken,
9       Tcl_GetCommandInfo,  Tcl_GetCommandInfoFromToken,   Tcl_SetCommandInfo,
10       Tcl_SetCommandInfoFromToken,   Tcl_GetCommandName,  Tcl_GetCommandFull‐
11       Name, Tcl_GetCommandFromObj - implement new commands in C
12

SYNOPSIS

14       #include <tcl.h>
15
16       Tcl_Command
17       Tcl_CreateObjCommand(interp, cmdName, proc, clientData, deleteProc)
18
19       int
20       Tcl_DeleteCommand(interp, cmdName)
21
22       int
23       Tcl_DeleteCommandFromToken(interp, token)
24
25       int
26       Tcl_GetCommandInfo(interp, cmdName, infoPtr)
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28       int
29       Tcl_SetCommandInfo(interp, cmdName, infoPtr)
30
31       int
32       Tcl_GetCommandInfoFromToken(token, infoPtr)
33
34       int
35       Tcl_SetCommandInfoFromToken(token, infoPtr)
36
37       const char *
38       Tcl_GetCommandName(interp, token)
39
40       void
41       Tcl_GetCommandFullName(interp, token, objPtr)
42
43       Tcl_Command
44       Tcl_GetCommandFromObj(interp, objPtr)
45

ARGUMENTS

47       Tcl_Interp *interp (in)                     Interpreter  in  which   to
48                                                   create  a  new  command  or
49                                                   that contains a command.
50
51       char *cmdName (in)                          Name of command.
52
53       Tcl_ObjCmdProc *proc (in)                   Implementation of  the  new
54                                                   command:   proc   will   be
55                                                   called whenever cmdName  is
56                                                   invoked as a command.
57
58       ClientData clientData (in)                  Arbitrary one-word value to
59                                                   pass    to     proc     and
60                                                   deleteProc.
61
62       Tcl_CmdDeleteProc *deleteProc (in)          Procedure  to  call  before
63                                                   cmdName is deleted from the
64                                                   interpreter;   allows   for
65                                                   command-specific   cleanup.
66                                                   If  NULL, then no procedure
67                                                   is called before  the  com‐
68                                                   mand is deleted.
69
70       Tcl_Command token (in)                      Token for command, returned
71                                                   by   previous    call    to
72                                                   Tcl_CreateObjCommand.   The
73                                                   command must not have  been
74                                                   deleted.
75
76       Tcl_CmdInfo *infoPtr (in/out)               Pointer  to  structure con‐
77                                                   taining various information
78                                                   about a Tcl command.
79
80       Tcl_Obj *objPtr (in)                        Object  containing the name
81                                                   of a Tcl command.
82_________________________________________________________________
83

DESCRIPTION

85       Tcl_CreateObjCommand defines a new command in interp and associates  it
86       with procedure proc such that whenever name is invoked as a Tcl command
87       (e.g., via a call to Tcl_EvalObjEx) the Tcl interpreter will call  proc
88       to process the command.
89
90       Tcl_CreateObjCommand  deletes any existing command name already associ‐
91       ated with the interpreter (however see below for an exception where the
92       existing  command is not deleted).  It returns a token that may be used
93       to refer to the command in subsequent calls to Tcl_GetCommandName.   If
94       name contains any :: namespace qualifiers, then the command is added to
95       the specified namespace; otherwise the command is added to  the  global
96       namespace.   If  Tcl_CreateObjCommand is called for an interpreter that
97       is in the process of being deleted, then it does not create a new  com‐
98       mand  and  it returns NULL.  proc should have arguments and result that
99       match the type Tcl_ObjCmdProc:
100              typedef int Tcl_ObjCmdProc(
101                      ClientData clientData,
102                      Tcl_Interp *interp,
103                      int objc,
104                      Tcl_Obj *const objv[]);
105       When proc is invoked, the clientData  and  interp  parameters  will  be
106       copies  of  the clientData and interp arguments given to Tcl_CreateObj‐
107       Command.  Typically, clientData points to an application-specific  data
108       structure  that  describes  what  to  do  when the command procedure is
109       invoked. Objc and objv describe the arguments to the command, objc giv‐
110       ing  the  number  of  argument objects (including the command name) and
111       objv giving the values of the arguments.  The objv array  will  contain
112       objc  values, pointing to the argument objects.  Unlike argv[argv] used
113       in a string-based command procedure, objv[objc] will not contain NULL.
114
115       Additionally, when proc is invoked, it must not modify the contents  of
116       the  objv  array  by assigning new pointer values to any element of the
117       array (for example, objv[2] = NULL) because this will cause  memory  to
118       be lost and the runtime stack to be corrupted.  The const in the decla‐
119       ration of objv will cause ANSI-compliant compilers to report  any  such
120       attempted  assignment as an error.  However, it is acceptable to modify
121       the internal representation of any  individual  object  argument.   For
122       instance,  the user may call Tcl_GetIntFromObj on objv[2] to obtain the
123       integer representation of that object; that call may change the type of
124       the  object  that  objv[2] points at, but will not change where objv[2]
125       points.
126
127       proc must return an integer code  that  is  either  TCL_OK,  TCL_ERROR,
128       TCL_RETURN,  TCL_BREAK, or TCL_CONTINUE.  See the Tcl overview man page
129       for details on what these codes mean.  Most normal commands  will  only
130       return  TCL_OK  or  TCL_ERROR.   In addition, if proc needs to return a
131       non-empty result, it can call Tcl_SetObjResult to set the interpreter's
132       result.   In  the case of a TCL_OK return code this gives the result of
133       the command, and in the case of TCL_ERROR this gives an error  message.
134       Before  invoking  a command procedure, Tcl_EvalObjEx sets interpreter's
135       result to point to an object representing an empty  string,  so  simple
136       commands can return an empty result by doing nothing at all.
137
138       The  contents of the objv array belong to Tcl and are not guaranteed to
139       persist once proc returns: proc should not modify them.  Call Tcl_SetO‐
140       bjResult if you want to return something from the objv array.
141
142       Ordinarily,  Tcl_CreateObjCommand  deletes  any  existing  command name
143       already associated with the interpreter.  However, if the existing com‐
144       mand was created by a previous call to Tcl_CreateCommand, Tcl_CreateOb‐
145       jCommand does not delete the command but instead arranges for  the  Tcl
146       interpreter  to  call  the  Tcl_ObjCmdProc proc in the future.  The old
147       string-based Tcl_CmdProc associated with the command  is  retained  and
148       its  address  can  be  obtained by subsequent Tcl_GetCommandInfo calls.
149       This is done for backwards compatibility.
150
151       DeleteProc will be invoked when (if) name is deleted.  This  can  occur
152       through  a  call  to  Tcl_DeleteCommand, Tcl_DeleteCommandFromToken, or
153       Tcl_DeleteInterp, or by replacing name in another call to Tcl_CreateOb‐
154       jCommand.   DeleteProc  is  invoked  before the command is deleted, and
155       gives the application an opportunity to release any structures  associ‐
156       ated  with  the  command.   DeleteProc should have arguments and result
157       that match the type Tcl_CmdDeleteProc:
158              typedef void Tcl_CmdDeleteProc(
159                      ClientData clientData);
160       The clientData argument will be the same  as  the  clientData  argument
161       passed to Tcl_CreateObjCommand.
162
163       Tcl_DeleteCommand  deletes  a command from a command interpreter.  Once
164       the call completes, attempts to invoke cmdName in interp will result in
165       errors.   If  cmdName  is  not  bound  as  a  command  in  interp  then
166       Tcl_DeleteCommand does nothing and returns -1;  otherwise it returns 0.
167       There  are no restrictions on cmdName:  it may refer to a built-in com‐
168       mand, an application-specific command, or a  Tcl  procedure.   If  name
169       contains  any  :: namespace qualifiers, the command is deleted from the
170       specified namespace.
171
172       Given a token returned by Tcl_CreateObjCommand,  Tcl_DeleteCommandFrom‐
173       Token deletes the command from a command interpreter.  It will delete a
174       command even if that command has been  renamed.   Once  the  call  com‐
175       pletes, attempts to invoke the command in interp will result in errors.
176       If the command corresponding to token has  already  been  deleted  from
177       interp then Tcl_DeleteCommand does nothing and returns -1; otherwise it
178       returns 0.
179
180       Tcl_GetCommandInfo checks to see whether its cmdName argument exists as
181       a  command  in  interp.  cmdName may include :: namespace qualifiers to
182       identify a command in a particular namespace.  If the  command  is  not
183       found,  then  it  returns 0.  Otherwise it places information about the
184       command in the Tcl_CmdInfo structure pointed to by infoPtr and  returns
185       1.  A Tcl_CmdInfo structure has the following fields:
186              typedef struct Tcl_CmdInfo {
187                  int isNativeObjectProc;
188                  Tcl_ObjCmdProc *objProc;
189                  ClientData objClientData;
190                  Tcl_CmdProc *proc;
191                  ClientData clientData;
192                  Tcl_CmdDeleteProc *deleteProc;
193                  ClientData deleteData;
194                  Tcl_Namespace *namespacePtr;
195              } Tcl_CmdInfo;
196       The  isNativeObjectProc  field  has the value 1 if Tcl_CreateObjCommand
197       was called to register the command; it is 0 if  only  Tcl_CreateCommand
198       was  called.   It allows a program to determine whether it is faster to
199       call objProc or proc: objProc is normally faster if  isNativeObjectProc
200       has  the  value  1.  The fields objProc and objClientData have the same
201       meaning as the proc and clientData arguments  to  Tcl_CreateObjCommand;
202       they hold information about the object-based command procedure that the
203       Tcl interpreter calls to implement the command.  The  fields  proc  and
204       clientData  hold  information  about the string-based command procedure
205       that implements the command.  If Tcl_CreateCommand was called for  this
206       command,  this is the procedure passed to it; otherwise, this is a com‐
207       patibility procedure registered  by  Tcl_CreateObjCommand  that  simply
208       calls  the command's object-based procedure after converting its string
209       arguments to Tcl objects.  The field deleteData is the ClientData value
210       to  pass  to deleteProc;  it is normally the same as clientData but may
211       be set independently using the Tcl_SetCommandInfo procedure.  The field
212       namespacePtr  holds  a  pointer  to the Tcl_Namespace that contains the
213       command.
214
215       Tcl_GetCommandInfoFromToken is identical to  Tcl_GetCommandInfo  except
216       that  it  uses  a  command  token returned from Tcl_CreateObjCommand in
217       place of the command name.  If the token parameter is NULL, it  returns
218       0;  otherwise,  it  returns  1 and fills in the structure designated by
219       infoPtr.
220
221       Tcl_SetCommandInfo is used to modify the procedures and ClientData val‐
222       ues  associated  with a command.  Its cmdName argument is the name of a
223       command in interp.  cmdName may  include  ::  namespace  qualifiers  to
224       identify a command in a particular namespace.  If this command does not
225       exist then Tcl_SetCommandInfo returns  0.   Otherwise,  it  copies  the
226       information  from  *infoPtr to Tcl's internal structure for the command
227       and returns 1.
228
229       Tcl_SetCommandInfoFromToken is identical to  Tcl_SetCommandInfo  except
230       that  it  takes  a  command  token  as returned by Tcl_CreateObjCommand
231       instead of the command name.   If  the  token  parameter  is  NULL,  it
232       returns 0.  Otherwise, it copies the information from *infoPtr to Tcl's
233       internal structure for the command and returns 1.
234
235       Note that Tcl_SetCommandInfo and Tcl_SetCommandInfoFromToken both allow
236       the ClientData for a command's deletion procedure to be given a differ‐
237       ent value than the ClientData for its command procedure.
238
239       Note that neither  Tcl_SetCommandInfo  nor  Tcl_SetCommandInfoFromToken
240       will  change  a  command's  namespace.  Use Tcl_Eval to call the rename
241       command to do that.
242
243       Tcl_GetCommandName provides a mechanism for tracking commands that have
244       been  renamed.  Given a token returned by Tcl_CreateObjCommand when the
245       command was created, Tcl_GetCommandName returns the string name of  the
246       command.   If  the  command has been renamed since it was created, then
247       Tcl_GetCommandName returns  the  current  name.   This  name  does  not
248       include  any  ::  namespace  qualifiers.   The command corresponding to
249       token must not have been deleted.  The string returned  by  Tcl_GetCom‐
250       mandName  is  in  dynamic memory owned by Tcl and is only guaranteed to
251       retain its value as long as the command  is  not  deleted  or  renamed;
252       callers should copy the string if they need to keep it for a long time.
253
254       Tcl_GetCommandFullName  produces  the fully qualified name of a command
255       from a command token.  The name, including all namespace  prefixes,  is
256       appended to the object specified by objPtr.
257
258       Tcl_GetCommandFromObj  returns a token for the command specified by the
259       name in a Tcl_Obj.  The command name is resolved relative to  the  cur‐
260       rent namespace.  Returns NULL if the command is not found.
261

SEE ALSO

263       Tcl_CreateCommand, Tcl_ResetResult, Tcl_SetObjResult
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265

KEYWORDS

267       bind, command, create, delete, namespace, object
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270
271Tcl                                   8.0              Tcl_CreateObjCommand(3)
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