Tcl_SetVar(3Tcl)Tcl_SetVar(3Tcl)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 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 operation.
See below for valid values.
char *name1 (in) Name of scalar variable, or name of
array 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.
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Tcl_SetVar(3Tcl)Tcl_SetVar(3Tcl)DESCRIPTION
These procedures may be used to create, modify, read, and delete Tcl
variables from C code. 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), 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 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 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 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 sublist (i.e. |
the variable's current value is empty, or contains the single |
character ``{'', or ends in `` }'').
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Tcl_SetVar(3Tcl)Tcl_SetVar(3Tcl)
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 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_TraceVar
KEYWORDS
array, interpreter, scalar, set, unset, variable
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