Tcl_ObjSetVar2

Tcl_ObjSetVar2, Tcl_ObjGetVar2 ? manipulate Tcl variables

#include <tcl.h>

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

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

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These two procedures may be used to read and modify Tcl variables from C code. Tcl_ObjSetVar2 will create a new variable or modify an existing one. It sets the specified variable to the object referenced by newValuePtr and returns a pointer to the object which is the variable’s new value. The returned object may not be the same one referenced by newValuePtr; this might happen because variable traces may modify the variable’s value. The reference count for the variable’s old value is decremented and the reference count for its new value is incremented. If the new value for the variable is not the same one referenced by newValuePtr (perhaps as a result of a variable trace), then newValuePtr’s reference count is left unchanged. The reference count for the returned object is not incremented to reflect the returned reference. If the caller needs to keep a reference to the object, say in a data structure, it must increment its reference count using Tcl_IncrRefCount. If an error occurs in setting the variable (e.g. an array variable is referenced without giving an index into the array), then NULL is returned.

The variable name specified to Tcl_ObjSetVar2 consists of two parts. part1Ptr contains the name of a scalar or array variable. If part2Ptr is NULL, the variable must be a scalar. If part2Ptr is not NULL, it contains the name of an element in the array named by part2Ptr. As a special case, if the flag TCL_PARSE_PART1 is specified, part1Ptr may contain both an array and an element name: if the name contains an open parenthesis and ends with a close parenthesis, then the value between the parentheses is treated as an element name (which can have any string value) and the characters before the first open parenthesis are treated as the name of an array variable. If the flag TCL_PARSE_PART1 is given, part2Ptr should be NULL since the array and element names are taken from part2Ptr.

The flags argument may be used to specify any of several options to the procedures. It consists of an OR-ed combination of any 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, a variable is looked up at the current level of procedure call. Otherwise, a 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

Under normal circumstances the procedures look up variables as follows: If a procedure call is active in interp, a variable is looked up at the current level of procedure call. Otherwise, a 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 current namespace even if there is a procedure call active.

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 is appended to the current value, instead of replacing it. If the variable is currently undefined, then this bit is ignored.

TCL_LIST_ELEMENT

If this bit is set, then newValuePtr 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_PARSE_PART1

If this bit is set, then Tcl_ObjGetVar2 and Tcl_ObjSetVar2 will parse part1Ptr to obtain both an array name and an element name. If the name in part1Ptr contains an open parenthesis and ends with a close parenthesis, the name is treated as the name of an element of an array; otherwise, the name in part1Ptr is interpreted as the name of a scalar variable. When this bit is set, part2Ptr is ignored.

Tcl_ObjGetVar2 returns the value of the specified variable. Its arguments are treated the same way as those for Tcl_ObjSetVar2. It returns a pointer to the object which is the variable’s value. The reference count for the returned object is not incremented. If the caller needs to keep a reference to the object, say in a data structure, it must increment the reference count using Tcl_IncrRefCount. If an error occurs in setting the variable (e.g. an array variable is referenced without giving an index into the array), then NULL is returned.

Tcl_GetObjResult, Tcl_GetStringResult, Tcl_GetVar, Tcl_GetVar2, Tcl_SetVar, Tcl_SetVar2, Tcl_TraceVar, Tcl_UnsetVar, Tcl_UnsetVar2

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