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 value 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 value 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 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 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, scalar, set, unset, value, variable