Version 0 of Tcl_CreateObjCommand

Updated 2006-09-19 10:36:24 by TR

TR - This C function is used to create a new command useable from the Tcl script level. The definition is

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

so it returns a Tcl_Command (which is a token for the command) and takes 5 arguments:

  • interp - the interpreter in which to create the new command
  • cmdName - the name of the new command (possibly in a specific namespace)
  • proc - the name of a C function to handle the command execution when called by a script
  • clientData - some data associated with the command, when a state needs to be taken care of (a file for example)
  • deleteProc - a C function to call when the command is deleted from the interpreter (used for cleanup)

A full example of the usage can be found in: Hello World as a C extension. Here is an example from the sqlite extension used to create the 'sqlite' command:

 Tcl_CreateObjCommand(interp, "sqlite", (Tcl_ObjCmdProc*)DbMain, 0, 0);

An example using the clientData feature is here (also from sqlite):

 Tcl_CreateObjCommand(interp, zArg, DbObjCmd, (char*)p, DbDeleteCmd);

Here, the clientData are used to "bind" the created command to the database file for which is was created. In this example zArgs is a variable to hold the name of the created command. The command will be handled by the DbObjCmd C function and the clientData are "(char*)p" in this case holding the data for the opened sqlite database, so the otherwise generic DbObjCmd function can operate on the right database file.

Category Tcl Library