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)

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.
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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

Tcl 8.1 Tcl_SetVar(3)