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Tcl_SetVar(3)               Tcl Library Procedures               Tcl_SetVar(3)



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NAME
       Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, Tcl_ObjSetVar2, Tcl_GetVar2Ex, Tcl_GetVar, Tcl_GetVar2, Tcl_ObjGetVar2,
       Tcl_UnsetVar, Tcl_UnsetVar2 - manipulate Tcl variables

SYNOPSIS
       #include <tcl.h>

       Tcl_Obj *
       Tcl_SetVar2Ex(interp, name1, name2, newValuePtr, flags)

       const char *
       Tcl_SetVar(interp, varName, newValue, flags)

       const char *
       Tcl_SetVar2(interp, name1, name2, newValue, flags)

       Tcl_Obj *
       Tcl_ObjSetVar2(interp, part1Ptr, part2Ptr, newValuePtr, flags)

       Tcl_Obj *
       Tcl_GetVar2Ex(interp, name1, name2, flags)

       const char *
       Tcl_GetVar(interp, varName, flags)

       const char *
       Tcl_GetVar2(interp, name1, name2, flags)

       Tcl_Obj *
       Tcl_ObjGetVar2(interp, part1Ptr, part2Ptr, flags)

       int
       Tcl_UnsetVar(interp, varName, flags)

       int
       Tcl_UnsetVar2(interp, name1, name2, flags)

ARGUMENTS
       Tcl_Interp *interp (in)               Interpreter containing variable.

       const char *name1 (in)                Contains the name of an array variable (if  name2  is  non-NULL)  or  (if
                                             name2  is  NULL)  either the name of a scalar variable or a complete name
                                             including both variable name and index.  May include :: namespace  quali-
                                             fiers to specify a variable in a particular namespace.

       const char *name2 (in)                If  non-NULL, gives name of element within array; in this case name1 must
                                             refer to an array variable.

       Tcl_Obj *newValuePtr (in)             Points to a Tcl object containing the new value for the variable.

       int flags (in)                        OR-ed combination of bits providing additional information. See below for
                                             valid values.

       const char *varName (in)              Name of variable.  May include :: namespace qualifiers to specify a vari-
                                             able in a particular namespace.  May refer to a  scalar  variable  or  an
                                             element of an array.

       const char *newValue (in)             New value for variable, specified as a null-terminated string.  A copy of
                                             this value is stored in the variable.

       Tcl_Obj *part1Ptr (in)                Points to a Tcl object containing the  variable's  name.   The  name  may
                                             include  a  series  of :: namespace qualifiers to specify a variable in a
                                             particular namespace.  May refer to a scalar variable or an element of an
                                             array variable.

       Tcl_Obj *part2Ptr (in)                If non-NULL, points to an object containing the name of an element within
                                             an array and part1Ptr must refer to an array variable.
______________________________________________________________________________________________________________________


DESCRIPTION
       These procedures are used to create, modify, read, and delete Tcl variables from C code.

       Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, and Tcl_ObjSetVar2 will create a new variable  or  modify  an  existing
       one.   These  procedures  set  the  given  variable  to the value given by newValuePtr or newValue and return a
       pointer to the variable's  new  value,  which  is  stored  in  Tcl's  variable  structure.   Tcl_SetVar2Ex  and
       Tcl_ObjSetVar2  take  the new value as a Tcl_Obj and return a pointer to a Tcl_Obj.  Tcl_SetVar and Tcl_SetVar2
       take the new value as a string and return a string; they are usually less efficient than Tcl_ObjSetVar2.   Note
       that  the return value may be different than the newValuePtr or newValue argument, due to modifications made by
       write traces.  If an error occurs in setting the variable (e.g. an array variable is referenced without  giving
       an  index  into  the  array)  NULL  is  returned  and  an  error  message  is  left  in  interp's result if the
       TCL_LEAVE_ERR_MSG flag bit is set.

       Tcl_GetVar2Ex, Tcl_GetVar, Tcl_GetVar2, and Tcl_ObjGetVar2 return the current value of a variable.   The  argu-
       ments  to  these  procedures  are  treated  in the same way as the arguments to the procedures described above.
       Under normal circumstances, the return value is a pointer to  the  variable's  value.   For  Tcl_GetVar2Ex  and
       Tcl_ObjGetVar2  the  value  is returned as a pointer to a Tcl_Obj.  For Tcl_GetVar and Tcl_GetVar2 the value is
       returned as a string; this is usually less efficient, so Tcl_GetVar2Ex or Tcl_ObjGetVar2 are preferred.  If  an
       error  occurs while reading the variable (e.g. the variable does not exist or an array element is specified for
       a scalar variable),  then  NULL  is  returned  and  an  error  message  is  left  in  interp's  result  if  the
       TCL_LEAVE_ERR_MSG flag bit is set.

       Tcl_UnsetVar  and  Tcl_UnsetVar2 may be used to remove a variable, so that future attempts to read the variable
       will return an error.  The arguments to these procedures are treated in the same way as the  arguments  to  the
       procedures  above.  If the variable is successfully removed then TCL_OK is returned.  If the variable cannot be
       removed because it does not exist then TCL_ERROR is returned and an error message is left in interp's result if
       the  TCL_LEAVE_ERR_MSG flag bit is set.  If an array element is specified, the given element is removed but the
       array remains.  If an array name is specified without an index, then the entire array is removed.

       The name of a variable may be specified to these procedures in four ways:

       [1]    If Tcl_SetVar, Tcl_GetVar, or Tcl_UnsetVar is invoked, the variable name is given as  a  single  string,
              varName.   If  varName  contains  an  open parenthesis and ends with a close parenthesis, then the value
              between the parentheses is treated as an index (which can have any  string  value)  and  the  characters
              before  the  first  open  parenthesis are treated as the name of an array variable.  If varName does not
              have parentheses as described above, then the entire string is treated as the name of a scalar variable.

       [2]    If  the name1 and name2 arguments are provided and name2 is non-NULL, then an array element is specified
              and the array name and index have already been separated by the caller:  name1  contains  the  name  and
              name2  contains the index.  An error is generated if name1  contains an open parenthesis and ends with a
              close parenthesis (array element) and name2 is non-NULL.

       [3]    If name2 is NULL, name1 is treated just like varName in case [1] above (it can be either a scalar or  an
              array element variable name).

       The  flags  argument  may be used to specify any of several options to the procedures.  It consists of an OR-ed
       combination of the following bits.

       TCL_GLOBAL_ONLY
              Under normal circumstances the procedures look up variables as follows.  If a procedure call  is  active
              in interp, the variable is looked up at the current level of procedure call.  Otherwise, the variable is
              looked up first in the current namespace, then in the global namespace.  However, if this bit is set  in
              flags  then  the  variable  is  looked up only in the global namespace even if there is a procedure call
              active.  If both TCL_GLOBAL_ONLY and TCL_NAMESPACE_ONLY are given, TCL_GLOBAL_ONLY is ignored.

       TCL_NAMESPACE_ONLY
              If this bit is set in flags then the variable is looked up only in the current namespace; if a procedure
              is  active  its variables are ignored, and the global namespace is also ignored unless it is the current
              namespace.

       TCL_LEAVE_ERR_MSG
              If an error is returned and this bit is set in flags, then an error message will be left in  the  inter-
              preter's  result,  where it can be retrieved with Tcl_GetObjResult or Tcl_GetStringResult.  If this flag
              bit is not set then no error message is left and the interpreter's result will not be modified.

       TCL_APPEND_VALUE
              If this bit is set then newValuePtr or newValue is appended to the current value  instead  of  replacing
              it.   If  the  variable  is  currently undefined, then the bit is ignored.  This bit is only used by the
              Tcl_Set* procedures.

       TCL_LIST_ELEMENT
              If this bit is set, then newValue is converted to a valid Tcl list element before setting (or  appending
              to)  the variable.  A separator space is appended before the new list element unless the list element is
              going to be the first element in a list or sublist (i.e. the variable's current value is empty, or  con-
              tains  the  single  character "{", or ends in " }").  When appending, the original value of the variable
              must also be a valid list, so that the operation is the appending of a new list element onto a list.

       Tcl_GetVar and Tcl_GetVar2 return the current value of a variable.   The  arguments  to  these  procedures  are
       treated in the same way as the arguments to Tcl_SetVar and Tcl_SetVar2.  Under normal circumstances, the return
       value is a pointer to the variable's value (which is stored in Tcl's variable structure  and  will  not  change
       before  the  next  call  to  Tcl_SetVar  or  Tcl_SetVar2).   Tcl_GetVar  and  Tcl_GetVar2  use  the  flag  bits
       TCL_GLOBAL_ONLY and TCL_LEAVE_ERR_MSG, both of which have the same meaning as  for  Tcl_SetVar.   If  an  error
       occurs  in reading the variable (e.g. the variable does not exist or an array element is specified for a scalar
       variable), then NULL is returned.

       Tcl_UnsetVar and Tcl_UnsetVar2 may be used to remove a variable, so that future calls to Tcl_GetVar or Tcl_Get-
       Var2  for  the variable will return an error.  The arguments to these procedures are treated in the same way as
       the arguments to Tcl_GetVar and Tcl_GetVar2.  If the variable is successfully removed then TCL_OK is  returned.
       If the variable cannot be removed because it does not exist then TCL_ERROR is returned.  If an array element is
       specified, the given element is removed but the array remains.  If an array name is specified without an index,
       then the entire array is removed.


SEE ALSO
       Tcl_GetObjResult, Tcl_GetStringResult, Tcl_TraceVar


KEYWORDS
       array, get variable, interpreter, object, scalar, set, unset, variable



Tcl                                   8.1                        Tcl_SetVar(3)