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
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 variable 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 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 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 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 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_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 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