Tcl_SetVar(3) Tcl Library Procedures Tcl_SetVar(3)______________________________________________________________________________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 qualifiers
to specify a variable in a par‐
ticular namespace.
const 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 value containing
the new value for the variable.
int flags (in) OR-ed combination of bits provid‐
ing additional information. See
below for valid values.
const 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.
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 value 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 a value
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 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 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
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 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 does not 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 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 contains
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 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 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_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 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, scalar, set, unset, value, variable
Tcl 8.1 Tcl_SetVar(3)
