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Tcl_SetVar

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)                 |

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

       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)                              |

       char *
       Tcl_GetVar(interp, varName, flags)

       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.

       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  qualifiers
                                             to  specify  a variable in a par-
                                             ticular namespace.

       char         *name2         (in)      If non-NULL, gives name  of  ele-
                                             ment  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 provid-
                                             ing  additional  information. See
                                             below for valid values.

       char         *varName       (in)      Name of variable.  May include ::
                                             namespace qualifiers to specify a
                                             variable in a  particular  names-
                                             pace.   May  refer  to  a  scalar
                                             variable  or  an  element  of  an
                                             array.  If the name references an
                                             element of  an  array,  then  the
                                             name  must be in writable memory:
                                             Tcl will make temporary modifica-
                                             tions  to it while looking up the
                                             name.

       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 :: names-
                                             pace  qualifiers  to  specify   a
                                             variable  in  a particular names-
                                             pace.   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 vari-
       ables 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 vari- |
       able 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_Set- |
       Var2 take the new value as a string and return a string; they are  usu- |
       ally  less  efficient  than Tcl_ObjSetVar2.  Note that the return value |
       may be different than the newValuePtr or newValue argument, due to mod-
       ifications  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 arguments 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 doesn't 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 argu-
       ments to the procedures above.  If the variable is successfully removed
       then  TCL_OK is returned.  If the variable cannot be removed because it
       doesn't 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 vari-
              able name is given as a single string, varName.  If varName con-
              tains  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 vari-
              able.   If  varName doesn't have parentheses as described above,
              then the entire string is treated as the name of a scalar  vari-
              able.

       [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 paren- |
              thesis (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 interpreter's result, where it
              can  be  retrieved with Tcl_GetObjResult or Tcl_GetStringResult.
              If this flag bit isn't 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 contains
              the single character ``{'', or ends in `` }'').

       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  argu-
       ments  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 doesn't 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_GetVar2 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 vari-
       able is successfully removed then TCL_OK is returned.  If the  variable
       cannot  be removed because it doesn't 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)