Tcl_SetVar(3) Tcl Library Procedures Tcl_SetVar(3)_________________________________________________________________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
refer to a scalar vari-
able 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 addi-
tional information for
operation. See below
for valid values.
char *name1 (in) Name of scalar vari-
able, or name of array
Tcl 7.4 1
Tcl_SetVar(3) Tcl Library Procedures Tcl_SetVar(3)
variable if name2 is
non-NULL.
char *name2 (in) If non-NULL, gives name
of element within array
and name1 must refer to
an array variable.
_________________________________________________________________DESCRIPTION
These procedures may be used to create, modify, read, and
delete Tcl variables from C code. Tcl_SetVar and Tcl_Set-
Var2 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 vari-
able'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), then NULL is returned.
The name of the variable may be specified 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 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 respec-
tively; 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 combi-
nation of any of the following bits:
TCL_GLOBAL_ONLY
Under normal circumstances the procedures look up
variables at the current level of procedure call
for interp, or at global level if there is no call
active. However, if this bit is set in flags then
the variable is looked up at global level 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
Tcl 7.4 2
Tcl_SetVar(3) Tcl Library Procedures Tcl_SetVar(3)
interp->result. If this flag bit isn't set then no
error message is left (interp->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 new list element unless the list element
is going to be the first element in a list or sub-
list (i.e. the variable's current value is empty,
or contains the single character ``{'', or ends in
`` }'').
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). The only bits of
flags that are used are 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 vari-
able (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_Get-
Var2 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_TraceVar
KEYWORDS
array, interpreter, scalar, set, unset, variable
Tcl 7.4 3
