TclSetResult(3) Tcl Library Procedures TclSetResult(3)

NAME
       TclSetObjResult, TclGetObjResult, TclSetResult, TclGetStringResult,
       TclAppendResult, TclAppendResultVA,  TclAppendElement,  TclResetRe-
       sult, TclFreeResult - manipulate Tcl result

SYNOPSIS
       ##iinncclluuddee <>

       TTccllSSeettOObbjjRReessuulltt(interp, objPtr)

       TclObj *
       TTccllGGeettOObbjjRReessuulltt(interp)

       TTccllSSeettRReessuulltt(interp, string, freeProc)

       CONST char *
       TTccllGGeettSSttrriinnggRReessuulltt(interp)

       TTccllAAppppeennddRReessuulltt(interp, string, string, ... , ((cchhaarr **)) NNUULLLL)

       TTccllAAppppeennddRReessuullttVVAA(interp, argList)

       TTccllAAppppeennddEElleemmeenntt(interp, string)

       TTccllRReesseettRReessuulltt(interp)

       TTccllFFrreeeeRReessuulltt(interp)

AARRGGUUMMEENNTTSS
       TclInterp     *interp    (out)     Interpreter  whose  result is to be
                                           modified or read.

       TclObj        *objPtr    (in)      Object value to become  result  for
                                           interp.

       char           *string    (in)      String  value  to become result for
                                           interp or to  be  appended  to  the
                                           existing result.

       TclFreeProc   *freeProc  (in)      Address  of  procedure  to  call to
                                           release  storage  at   string,   or
                                           TTCCLLSSTTAATTIICC,     TTCCLLDDYYNNAAMMIICC,     or
                                           TTCCLLVVOOLLAATTIILLEE.

       valist        argList    (in)      An argument list  which  must  have
                                           been        initialised       using
                                           TTCCLLVVAARRAARRGGSSSSTTAARRTT,   and    cleared
                                           using vvaaeenndd.



DESCRIPTION
       The procedures described here are utilities for manipulating the result
       value in a Tcl interpreter.  The interpreter result may be either a Tcl
       object  or  a  string.  For example, TTccllSSeettOObbjjRReessuulltt and TTccllSSeettRReessuulltt
       set the interpreter result to, respectively, an object  and  a  string.
       Similarly,  TTccllGGeettOObbjjRReessuulltt  and TTccllGGeettSSttrriinnggRReessuulltt return the inter-
       preter result as an object and as a string.  The procedures always keep
       the  string and object forms of the interpreter result consistent.  For
       example, if TTccllSSeettOObbjjRReessuulltt is called to set the result to an  object,
       then  TTccllGGeettSSttrriinnggRReessuulltt is called, it will return the object's string
       value.

       TTccllSSeettOObbjjRReessuulltt arranges for objPtr  to  be  the  result  for  interp,
       replacing  any  existing  result.   The  result is left pointing to the
       object referenced by objPtr.  objPtr's reference count  is  incremented
       since  there  is  now a new reference to it from interp.  The reference
       count for any old result object  is  decremented  and  the  old  result
       object is freed if no references to it remain.

       TTccllGGeettOObbjjRReessuulltt  returns  the  result  for  interp  as an object.  The
       object's reference count is not incremented; if  the  caller  needs  to
       retain  a  long-term pointer to the object they should use TTccllIInnccrrRReeff-
       CCoouunntt to increment its reference count in order to keep it  from  being
       freed too early or accidently changed.

       TTccllSSeettRReessuulltt  arranges for string to be the result for the current Tcl
       command in interp, replacing any existing result.  The  freeProc  argu-
       ment specifies how to manage the storage for the string argument; it is
       discussed in the section TTHHEE  TTCCLLFFRREEEEPPRROOCC  AARRGGUUMMEENNTT  TTOO  TTCCLLSSEETTRREESSUULLTT
       below.   If  string is NNUULLLL, then freeProc is ignored and TTccllSSeettRReessuulltt
       re-initializes interp's result to point to an empty string.

       TTccllGGeettSSttrriinnggRReessuulltt returns the result for interp as an string.  If the
       result was set to an object by a TTccllSSeettOObbjjRReessuulltt call, the object form
       will be converted to a string and returned.   If  the  object's  string
       representation  contains null bytes, this conversion will lose informa-
       tion.  For this reason, programmers are encouraged to write their  code
       to  use  the  new  object  API  procedures and to call TTccllGGeettOObbjjRReessuulltt
       instead.

       TTccllRReesseettRReessuulltt clears the result for interp and leaves the  result  in
       its  normal  empty  initialized state.  If the result is an object, its
       reference count is decremented and the result is left  pointing  to  an
       unshared  object  representing  an  empty  string.   If the result is a
       dynamically allocated string, its memory is free*d and  the  result  is
       left  as  a  empty string.  TTccllRReesseettRReessuulltt also clears the error state
       managed by TTccllAAddddEErrrroorrIInnffoo, TTccllAAddddOObbjjEErrrroorrIInnffoo, and TTccllSSeettEErrrroorrCCooddee.


OOLLDD SSTTRRIINNGG PPRROOCCEEDDUURREESS
       Use of the following procedures is deprecated since they manipulate the
       Tcl result as a  string.   Procedures  such  as  TTccllSSeettOObbjjRReessuulltt  that
       manipulate the result as an object can be significantly more efficient.

       TTccllAAppppeennddRReessuulltt makes it easy to build up Tcl results in  pieces.   It
       takes  each  of  its  string arguments and appends them in order to the
       current result associated with interp.  If the result is  in  its  ini-
       tialized  empty  state  (e.g.  a  command procedure was just invoked or
       TTccllRReesseettRReessuulltt was just called), then TTccllAAppppeennddRReessuulltt sets the result
       to  the concatenation of its string arguments.  TTccllAAppppeennddRReessuulltt may be
       called repeatedly as additional pieces  of  the  result  are  produced.
       TTccllAAppppeennddRReessuulltt  takes care of all the storage management issues asso-
       ciated with managing interp's  result,  such  as  allocating  a  larger
       result  area  if  necessary.   It also converts the current interpreter
       result from an object to a string, if necessary, before  appending  the
       argument  strings.   Any  number of string arguments may be passed in a
       single call; the last argument in the list must be a NULL pointer.

       TTccllAAppppeennddRReessuullttVVAA is the same as TTccllAAppppeennddRReessuulltt except that  instead
       of taking a variable number of arguments it takes an argument list.

       TTccllAAppppeennddEElleemmeenntt  is  similar  to  TTccllAAppppeennddRReessuulltt  in that it allows
       results to be built up in  pieces.   However,  TTccllAAppppeennddEElleemmeenntt  takes
       only  a single string argument and it appends that argument to the cur-
       rent result as a proper Tcl list element.  TTccllAAppppeennddEElleemmeenntt adds back-
       slashes  or  braces  if necessary to ensure that interp's result can be
       parsed as a list and that string will be extracted as a single element.
       Under  normal  conditions, TTccllAAppppeennddEElleemmeenntt will add a space character
       to interp's result just before adding the new list element, so that the
       list elements in the result are properly separated.  However if the new
       list element is the first in a list or sub-list (i.e. interp's  current
       result  is empty, or consists of the single character ``{'', or ends in
       the characters `` {'') then no space is added.

       TTccllFFrreeeeRReessuulltt performs part of the work of TTccllRReesseettRReessuulltt.  It  frees
       up   the   memory  associated  with  interp's  result.   It  also  sets
       interp->freeProc to zero, but doesn't change  interp->result  or  clear
       error  state.  TTccllFFrreeeeRReessuulltt is most commonly used when a procedure is
       about to replace one result value with another.


DDIIRREECCTT AACCCCEESSSS TTOO IINNTTEERRPP->>RREESSUULLTT IISS DDEEPPRREECCAATTEEDD
       It  used  to  be  legal  for  programs  to  directly  read  and   write
       interp->result  to manipulate the interpreter result.  Direct access to
       interp->result is now strongly  deprecated  because  it  can  make  the
       result's  string and object forms inconsistent.  Programs should always
       read the result  using  the  procedures  TTccllGGeettOObbjjRReessuulltt  or  TTccllGGeett-
       SSttrriinnggRReessuulltt, and write the result using TTccllSSeettOObbjjRReessuulltt or TTccllSSeettRRee-
       ssuulltt.


TTHHEE TTCCLLFFRREEEEPPRROOCC AARRGGUUMMEENNTT TTOO TTCCLLSSEETTRREESSUULLTT
       TTccllSSeettRReessuulltt's freeProc argument specifies how the Tcl  system  is  to
       manage  the  storage  for  the  string  argument.   If TTccllSSeettRReessuulltt or
       TTccllSSeettOObbjjRReessuulltt are called at  a  time  when  interp  holds  a  string
       result,  they  do  whatever  is  necessary to dispose of the old string
       result (see the TTccllIInntteerrpp manual entry for details on this).

       If freeProc is TTCCLLSSTTAATTIICC it means that string refers  to  an  area  of
       static storage that is guaranteed not to be modified until at least the
       next call to TTccllEEvvaall.  If freeProc is TTCCLLDDYYNNAAMMIICC it means that string
       was  allocated  with a call to TTccllAAlllloocc and is now the property of the
       Tcl system.  TTccllSSeettRReessuulltt will arrange for the string's storage to  be
       released  by calling TTccllFFrreeee when it is no longer needed.  If freeProc
       is TTCCLLVVOOLLAATTIILLEE it means that string points to an area of  memory  that
       is  likely to be overwritten when TTccllSSeettRReessuulltt returns (e.g. it points
       to something in a stack frame).  In this case TTccllSSeettRReessuulltt will make a
       copy of the string in dynamically allocated storage and arrange for the
       copy to be the result for the current Tcl command.

       If freeProc isn't  one  of  the  values  TTCCLLSSTTAATTIICC,  TTCCLLDDYYNNAAMMIICC,  and
       TTCCLLVVOOLLAATTIILLEE,  then  it  is  the address of a procedure that Tcl should
       call to free the string.  This allows applications to use  non-standard
       storage  allocators.   When  Tcl  no  longer  needs the storage for the
       string, it will call  freeProc.  FreeProc  should  have  arguments  and
       result that match the type TTccllFFrreeeePPrroocc:
              typedef void TclFreeProc(char *blockPtr);
       When  freeProc  is  called,  its  blockPtr  will be set to the value of
       string passed to TTccllSSeettRReessuulltt.


SEE ALSO
       TclAddErrorInfo, TclCreateObjCommand, TclSetErrorCode, TclInterp


KKEEYYWWOORRDDSS
       append, command, element, list, object, result,  return  value,  inter-
       preter



Tcl                                   8.0                     TclSetResult(3)