Tcl_SetVar (3)

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 *newValue 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 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.

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 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 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 '\" '\" Copyright (c) 1989-1993 The Regents of the University of California. '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) $Id: TraceVar.3,v 1.2 1998/09/14 18:39:50 stanton Exp $ '\" '\" The definitions below are for supplemental macros used in Tcl/Tk '\" manual entries. '\" '\" .AP type name in/out ?indent? '\" Start paragraph describing an argument to a library procedure. '\" type is type of argument (int, etc.), in/out is either "in", "out", '\" or "in/out" to describe whether procedure reads or modifies arg, '\" and indent is equivalent to second arg of .IP (shouldn't ever be '\" needed; use .AS below instead) '\" '\" .AS ?type? ?name? '\" Give maximum sizes of arguments for setting tab stops. Type and '\" name are examples of largest possible arguments that will be passed '\" to .AP later. If args are omitted, default tab stops are used. '\" '\" .BS '\" Start box enclosure. From here until next .BE, everything will be '\" enclosed in one large box. '\" '\" .BE '\" End of box enclosure. '\" '\" .CS '\" Begin code excerpt. '\" '\" .CE '\" End code excerpt. '\" '\" .VS ?version? ?br? '\" Begin vertical sidebar, for use in marking newly-changed parts '\" of man pages. The first argument is ignored and used for recording '\" the version when the .VS was added, so that the sidebars can be '\" found and removed when they reach a certain age. If another argument '\" is present, then a line break is forced before starting the sidebar. '\" '\" .VE '\" End of vertical sidebar. '\" '\" .DS '\" Begin an indented unfilled display. '\" '\" .DE '\" End of indented unfilled display. '\" '\" .SO '\" Start of list of standard options for a Tk widget. The '\" options follow on successive lines, in four columns separated '\" by tabs. '\" '\" .SE '\" End of list of standard options for a Tk widget. '\" '\" .OP cmdName dbName dbClass '\" Start of description of a specific option. cmdName gives the '\" option's name as specified in the class command, dbName gives '\" the option's name in the option database, and dbClass gives '\" the option's class in the option database. '\" '\" .UL arg1 arg2 '\" Print arg1 underlined, then print arg2 normally. '\" '\" RCS: @(#) $Id: man.macros,v 1.2 1998/09/14 18:39:54 stanton Exp $ '\" '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. t .wh -1.3i ^B ^l \n(.l b '\" # Start an argument description AP !"\\$4"" .TP \\$4 \{\ !"\\$2"" .TP \\n()Cu .TP 15