TclCreateCommand(3) Tcl Library Procedures TclCreateCommand(3)

NAME
       TclCreateCommand - implement new commands in C

SYNOPSIS
       ##iinncclluuddee <>

       TclCommand
       TTccllCCrreeaatteeCCoommmmaanndd(interp, cmdName, proc, clientData, deleteProc)

AARRGGUUMMEENNTTSS
       TclInterp          *interp           (in)      Interpreter in which to
                                                       create new command.     |

       CONST char          *cmd-                                               |
       Name          (in)                              |                       |
                                                       Name of command.

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

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

       TclCmdDeleteProc   *deleteProc       (in)      Procedure    to    call
                                                       before    cmdName    is
                                                       deleted from the inter-
                                                       preter; allows for com-
                                                       mand-specific  cleanup.
                                                       If NULL, then no proce-
                                                       dure  is  called before
                                                       the command is deleted.



DESCRIPTION
       TTccllCCrreeaatteeCCoommmmaanndd  defines  a  new  command in interp and associates it
       with procedure proc such that whenever cmdName is invoked as a Tcl com-
       mand  (via  a  call  to TTccllEEvvaall) the Tcl interpreter will call proc to
       process the command.  It differs from TTccllCCrreeaatteeOObbjjCCoommmmaanndd  in  that  a
       new  string-based  command  is defined; that is, a command procedure is
       defined that takes an array of argument  strings  instead  of  objects.
       The  object-based command procedures registered by TTccllCCrreeaatteeOObbjjCCoommmmaanndd
       can execute significantly faster than the string-based  command  proce-
       dures  defined  by  TTccllCCrreeaatteeCCoommmmaanndd.   This  is because they take Tcl
       objects as arguments and those objects can retain an internal represen-
       tation  that  can  be manipulated more efficiently.  Also, Tcl's inter-
       preter now uses objects internally.  In order to invoke a  string-based
       command procedure registered by TTccllCCrreeaatteeCCoommmmaanndd, it must generate and
       fetch a string representation from each argument object before the call
       and  create  a new Tcl object to hold the string result returned by the
       string-based command procedure.  New commands should be  defined  using
       TTccllCCrreeaatteeOObbjjCCoommmmaanndd.   We support TTccllCCrreeaatteeCCoommmmaanndd for backwards com-
       patibility.

       The procedures TTccllDDeelleetteeCCoommmmaanndd, TTccllGGeettCCoommmmaannddIInnffoo,  and  TTccllSSeettCCoomm-
       mmaannddIInnffoo are used in conjunction with TTccllCCrreeaatteeCCoommmmaanndd.

       TTccllCCrreeaatteeCCoommmmaanndd  will  delete  an existing command cmdName, if one is
       already associated with the interpreter.  It returns a token  that  may
       be  used to refer to the command in subsequent calls to TTccllGGeettCCoommmmaanndd-
       NNaammee.  If cmdName contains any :::: namespace qualifiers, then  the  com-
       mand  is  added  to  the  specified namespace; otherwise the command is
       added to the global namespace.  If TTccllCCrreeaatteeCCoommmmaanndd 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 TTccllCCmmddPPrroocc:
              typedef int TclCmdProc(
                ClientData clientData,
                TclInterp *interp,
                int argc,
                CONST char *argv[]);
       When  proc  is  invoked  the  clientData  and interp parameters will be
       copies of the clientData and interp arguments given  to  TTccllCCrreeaatteeCCoomm-
       mmaanndd.   Typically,  clientData  points  to an application-specific data
       structure that describes what to  do  when  the  command  procedure  is
       invoked.   Argc  and  argv  describe the arguments to the command, argc
       giving the number of arguments (including the command  name)  and  argv
       giving  the  values  of  the arguments as strings.  The argv array will
       contain argc+1 values; the first argc  values  point  to  the  argument
       strings,  and  the  last value is NULL.  Note that the argument strings |
       should not be modified as they may point to constant strings or may  be |
       shared with other parts of the interpreter.

       Note  that  the  argument strings are encoded in normalized UTF-8 since |
       version 8.1 of Tcl.

       Proc must return an integer code  that  is  either  TTCCLLOOKK,  TTCCLLEERRRROORR,
       TTCCLLRREETTUURRNN,  TTCCLLBBRREEAAKK, or TTCCLLCCOONNTTIINNUUEE.  See the Tcl overview man page
       for details on what these codes mean.  Most normal commands  will  only
       return TTCCLLOOKK or TTCCLLEERRRROORR.  In addition, proc must set the interpreter
       result to point to a string value; in the case of a TTCCLLOOKK return  code
       this  gives  the result of the command, and in the case of TTCCLLEERRRROORR it
       gives an error message.  The TTccllSSeettRReessuulltt procedure provides  an  easy
       interface  for  setting  the return value;  for complete details on how
       the the interpreter result field is managed,  see  the  TTccllIInntteerrpp  man
       page.   Before  invoking  a command procedure, TTccllEEvvaall sets the inter-
       preter result to point to an  empty  string,  so  simple  commands  can
       return an empty result by doing nothing at all.

       The  contents of the argv array belong to Tcl and are not guaranteed to
       persist once proc returns:  proc should not modify them, nor should  it
       set  the  interpreter  result to point anywhere within the argv values.
       Call TTccllSSeettRReessuulltt with status TTCCLLVVOOLLAATTIILLEE if you want to return some-
       thing from the argv array.

       DeleteProc  will  be  invoked  when  (if) cmdName is deleted.  This can
       occur through a call to TTccllDDeelleetteeCCoommmmaanndd or  TTccllDDeelleetteeIInntteerrpp,  or  by
       replacing  cmdName in another call to TTccllCCrreeaatteeCCoommmmaanndd.  DeleteProc is
       invoked before the command is deleted, and  gives  the  application  an
       opportunity  to  release  any  structures  associated with the command.
       DeleteProc should  have  arguments  and  result  that  match  the  type
       TTccllCCmmddDDeelleetteePPrroocc:
              typedef void TclCmdDeleteProc(ClientData clientData);
       The  clientData  argument  will  be the same as the clientData argument
       passed to TTccllCCrreeaatteeCCoommmmaanndd.



SEE ALSO
       TclCreateObjCommand, TclDeleteCommand,  TclGetCommandInfo,  TclSet-
       CommandInfo, TclGetCommandName, TclSetObjResult


KKEEYYWWOORRDDSS
       bind, command, create, delete, interpreter, namespace



Tcl                                                       TclCreateCommand(3)