Tcl_SetVar(3) Tcl (7.4) Tcl_SetVar(3)
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NAME
Tcl_SetVar, Tcl_SetVar2, Tcl_GetVar, Tcl_GetVar2,
Tcl_UnsetVar, Tcl_UnsetVar2 - manipulate Tcl variables
SYNOPSIS
#include <tcl.h>
char *
Tcl_SetVar(interp, varName, newValue, flags)
char *
Tcl_SetVar2(interp, name1, name2, newValue, flags)
char *
Tcl_GetVar(interp, varName, flags)
char *
Tcl_GetVar2(interp, name1, name2, flags)
int
Tcl_UnsetVar(interp, varName, flags)
int
Tcl_UnsetVar2(interp, name1, name2, flags)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter containing
variable.
char *varName (in) Name of variable. 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. If
the name references an
element of an array, then
it must be in writable
memory: Tcl will make
temporary modifications
to it while looking up
the name.
char *newValue (in) New value for variable.
int flags (in) OR-ed combination of bits
providing additional
information for
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Tcl_SetVar(3) Tcl (7.4) Tcl_SetVar(3)
operation. See below for
valid values.
char *name1 (in) Name of scalar variable,
or name of array variable
if name2 is non-NULL.
May include a series of
:: namespace qualifiers
to specify a variable in
a particular namespace.
char *name2 (in) If non-NULL, gives name
of element within array
and name1 must refer to
an array variable.
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DESCRIPTION
These procedures may be used to create, modify, read, and
delete Tcl variables from C code.
Note that Tcl_GetVar and Tcl_SetVar have been largely
replaced by the object-based procedures Tcl_ObjGetVar2 and
Tcl_ObjSetVar2. Those object-based procedures read, modify,
and create a variable whose name is held in a Tcl object
instead of a string. They also return a pointer to the
object which is the variable's value instead of returning a
string. Operations on objects can be faster since objects
hold an internal representation that can be manipulated more
efficiently.
Tcl_SetVar and Tcl_SetVar2 will create a new variable or
modify an existing one. Both of these procedures set the
given variable to the value given by newValue, and they
return a pointer to a copy of the variable's new value,
which is stored in Tcl's variable structure. Tcl keeps a
private copy of the variable's value, so the caller may
change newValue after these procedures return without
affecting the value of the variable. If an error occurs in
setting the variable (e.g. an array variable is referenced
without giving an index into the array), they return NULL.
The name of the variable may be specified to Tcl_SetVar and
Tcl_SetVar2 in either of two ways. If Tcl_SetVar is called,
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 doesn't have
parentheses as described above, then the entire string is
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Tcl_SetVar(3) Tcl (7.4) Tcl_SetVar(3)
treated as the name of a scalar variable. If Tcl_SetVar2 is
called, then the array name and index have been separated by
the caller into two separate strings, name1 and name2
respectively; if name2 is zero it means that a scalar
variable is being referenced.
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. Note that the flag bit
TCL_PARSE_PART1 is only meaningful for the procedures
Tcl_SetVar2 and Tcl_GetVar2.
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 newValue 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 newValue is converted to a
valid Tcl list element before setting (or appending to)
the variable. A separator space is appended before the
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Tcl_SetVar(3) Tcl (7.4) Tcl_SetVar(3)
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 when calling Tcl_SetVar2 and
Tcl_GetVar2, name1 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, name2 should be NULL since the array and
element names are taken from name1.
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. In addition,
Tcl_GetVar2 uses the bit TCL_PARSE_PART1, which has the same
meaning as for Tcl_SetVar2. If an error occurs in reading
the variable (e.g. the variable doesn't 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 doesn't 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_ObjGetVar2,
Tcl_ObjSetVar2, Tcl_TraceVar
KEYWORDS
array, interpreter, object, scalar, set, unset, variable
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