1Tcl_SetVar(3) Tcl Library Procedures Tcl_SetVar(3)
2______________________________________________________________________________
6
8 Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, Tcl_ObjSetVar2, Tcl_GetVar2Ex,
9 Tcl_GetVar, Tcl_GetVar2, Tcl_ObjGetVar2, Tcl_UnsetVar, Tcl_UnsetVar2 -
10 manipulate Tcl variables
11
13 #include <tcl.h>
14 Tcl_Obj *
16 Tcl_SetVar2Ex(interp, name1, name2, newValuePtr, flags)
17 const char *
19 Tcl_SetVar(interp, varName, newValue, flags)
20 const char *
22 Tcl_SetVar2(interp, name1, name2, newValue, flags)
23 Tcl_Obj *
25 Tcl_ObjSetVar2(interp, part1Ptr, part2Ptr, newValuePtr, flags)
26 Tcl_Obj *
28 Tcl_GetVar2Ex(interp, name1, name2, flags)
29 const char *
31 Tcl_GetVar(interp, varName, flags)
32 const char *
34 Tcl_GetVar2(interp, name1, name2, flags)
35 Tcl_Obj *
37 Tcl_ObjGetVar2(interp, part1Ptr, part2Ptr, flags)
38 int
40 Tcl_UnsetVar(interp, varName, flags)
41 int
43 Tcl_UnsetVar2(interp, name1, name2, flags)
44
46 Tcl_Interp *interp (in) Interpreter containing variable.
47 const char *name1 (in) Contains the name of an array
49 variable (if name2 is non-NULL)
50 or (if name2 is NULL) either the
51 name of a scalar variable or a
52 complete name including both
53 variable name and index. May
54 include :: namespace qualifiers
55 to specify a variable in a par‐
56 ticular namespace.
57 const char *name2 (in) If non-NULL, gives name of ele‐
59 ment within array; in this case
60 name1 must refer to an array
61 variable.
62 Tcl_Obj *newValuePtr (in) Points to a Tcl value containing
64 the new value for the variable.
65 int flags (in) OR-ed combination of bits provid‐
67 ing additional information. See
68 below for valid values.
69 const char *varName (in) Name of variable. May include ::
71 namespace qualifiers to specify a
72 variable in a particular names‐
73 pace. May refer to a scalar
74 variable or an element of an
75 array.
76 const char *newValue (in) New value for variable, specified
78 as a null-terminated string. A
79 copy of this value is stored in
80 the variable.
81 Tcl_Obj *part1Ptr (in) Points to a Tcl value containing
83 the variable's name. The name
84 may include a series of :: names‐
85 pace qualifiers to specify a
86 variable in a particular names‐
87 pace. May refer to a scalar
88 variable or an element of an
89 array variable.
90 Tcl_Obj *part2Ptr (in) If non-NULL, points to a value
92 containing the name of an element
93 within an array and part1Ptr must
94 refer to an array variable.
95______________________________________________________________________________
96
99 These procedures are used to create, modify, read, and delete Tcl vari‐
100 ables from C code.
101 Tcl_SetVar2Ex, Tcl_SetVar, Tcl_SetVar2, and Tcl_ObjSetVar2 will create
103 a new variable or modify an existing one. These procedures set the
104 given variable to the value given by newValuePtr or newValue and return
105 a pointer to the variable's new value, which is stored in Tcl's vari‐
106 able structure. Tcl_SetVar2Ex and Tcl_ObjSetVar2 take the new value as
107 a Tcl_Obj and return a pointer to a Tcl_Obj. Tcl_SetVar and Tcl_Set‐
108 Var2 take the new value as a string and return a string; they are usu‐
109 ally less efficient than Tcl_ObjSetVar2. Note that the return value
110 may be different than the newValuePtr or newValue argument, due to mod‐
111 ifications made by write traces. If an error occurs in setting the
112 variable (e.g. an array variable is referenced without giving an index
113 into the array) NULL is returned and an error message is left in
114 interp's result if the TCL_LEAVE_ERR_MSG flag bit is set.
115 Tcl_GetVar2Ex, Tcl_GetVar, Tcl_GetVar2, and Tcl_ObjGetVar2 return the
117 current value of a variable. The arguments to these procedures are
118 treated in the same way as the arguments to the procedures described
119 above. Under normal circumstances, the return value is a pointer to
120 the variable's value. For Tcl_GetVar2Ex and Tcl_ObjGetVar2 the value
121 is returned as a pointer to a Tcl_Obj. For Tcl_GetVar and Tcl_GetVar2
122 the value is returned as a string; this is usually less efficient, so
123 Tcl_GetVar2Ex or Tcl_ObjGetVar2 are preferred. If an error occurs
124 while reading the variable (e.g. the variable does not exist or an
125 array element is specified for a scalar variable), then NULL is
126 returned and an error message is left in interp's result if the
127 TCL_LEAVE_ERR_MSG flag bit is set.
128 Tcl_UnsetVar and Tcl_UnsetVar2 may be used to remove a variable, so
130 that future attempts to read the variable will return an error. The
131 arguments to these procedures are treated in the same way as the argu‐
132 ments to the procedures above. If the variable is successfully removed
133 then TCL_OK is returned. If the variable cannot be removed because it
134 does not exist then TCL_ERROR is returned and an error message is left
135 in interp's result if the TCL_LEAVE_ERR_MSG flag bit is set. If an
136 array element is specified, the given element is removed but the array
137 remains. If an array name is specified without an index, then the
138 entire array is removed.
139 The name of a variable may be specified to these procedures in four
141 ways:
142 [1] If Tcl_SetVar, Tcl_GetVar, or Tcl_UnsetVar is invoked, the vari‐
144 able name is given as a single string, varName. If varName con‐
145 tains an open parenthesis and ends with a close parenthesis,
146 then the value between the parentheses is treated as an index
147 (which can have any string value) and the characters before the
148 first open parenthesis are treated as the name of an array vari‐
149 able. If varName does not have parentheses as described above,
150 then the entire string is treated as the name of a scalar vari‐
151 able.
152 [2] If the name1 and name2 arguments are provided and name2 is non-
154 NULL, then an array element is specified and the array name and
155 index have already been separated by the caller: name1 contains
156 the name and name2 contains the index. An error is generated if
157 name1 contains an open parenthesis and ends with a close paren‐
158 thesis (array element) and name2 is non-NULL.
159 [3] If name2 is NULL, name1 is treated just like varName in case [1]
161 above (it can be either a scalar or an array element variable
162 name).
163 The flags argument may be used to specify any of several options to the
165 procedures. It consists of an OR-ed combination of the following bits.
166 TCL_GLOBAL_ONLY
168 Under normal circumstances the procedures look up variables as
169 follows. If a procedure call is active in interp, the variable
170 is looked up at the current level of procedure call. Otherwise,
171 the variable is looked up first in the current namespace, then
172 in the global namespace. However, if this bit is set in flags
173 then the variable is looked up only in the global namespace even
174 if there is a procedure call active. If both TCL_GLOBAL_ONLY
175 and TCL_NAMESPACE_ONLY are given, TCL_GLOBAL_ONLY is ignored.
176 TCL_NAMESPACE_ONLY
178 If this bit is set in flags then the variable is looked up only
179 in the current namespace; if a procedure is active its variables
180 are ignored, and the global namespace is also ignored unless it
181 is the current namespace.
182 TCL_LEAVE_ERR_MSG
184 If an error is returned and this bit is set in flags, then an
185 error message will be left in the interpreter's result, where it
186 can be retrieved with Tcl_GetObjResult or Tcl_GetStringResult.
187 If this flag bit is not set then no error message is left and
188 the interpreter's result will not be modified.
189 TCL_APPEND_VALUE
191 If this bit is set then newValuePtr or newValue is appended to
192 the current value instead of replacing it. If the variable is
193 currently undefined, then the bit is ignored. This bit is only
194 used by the Tcl_Set* procedures.
195 TCL_LIST_ELEMENT
197 If this bit is set, then newValue is converted to a valid Tcl
198 list element before setting (or appending to) the variable. A
199 separator space is appended before the new list element unless
200 the list element is going to be the first element in a list or
201 sublist (i.e. the variable's current value is empty, or contains
202 the single character “{”, or ends in “ }”). When appending, the
203 original value of the variable must also be a valid list, so
204 that the operation is the appending of a new list element onto a
205 list.
206 Tcl_GetVar and Tcl_GetVar2 return the current value of a variable. The
208 arguments to these procedures are treated in the same way as the argu‐
209 ments to Tcl_SetVar and Tcl_SetVar2. Under normal circumstances, the
210 return value is a pointer to the variable's value (which is stored in
211 Tcl's variable structure and will not change before the next call to
212 Tcl_SetVar or Tcl_SetVar2). Tcl_GetVar and Tcl_GetVar2 use the flag
213 bits TCL_GLOBAL_ONLY and TCL_LEAVE_ERR_MSG, both of which have the same
214 meaning as for Tcl_SetVar. If an error occurs in reading the variable
215 (e.g. the variable does not exist or an array element is specified for
216 a scalar variable), then NULL is returned.
217 Tcl_UnsetVar and Tcl_UnsetVar2 may be used to remove a variable, so
219 that future calls to Tcl_GetVar or Tcl_GetVar2 for the variable will
220 return an error. The arguments to these procedures are treated in the
221 same way as the arguments to Tcl_GetVar and Tcl_GetVar2. If the vari‐
222 able is successfully removed then TCL_OK is returned. If the variable
223 cannot be removed because it does not exist then TCL_ERROR is returned.
224 If an array element is specified, the given element is removed but the
225 array remains. If an array name is specified without an index, then
226 the entire array is removed.
227
230 Tcl_GetObjResult, Tcl_GetStringResult, Tcl_TraceVar
231
234 array, get variable, interpreter, scalar, set, unset, value, variable
235Tcl 8.1 Tcl_SetVar(3)