1Tcl_LinkVar(3) Tcl Library Procedures Tcl_LinkVar(3)
2______________________________________________________________________________
6
8 Tcl_LinkVar, Tcl_UnlinkVar, Tcl_UpdateLinkedVar - link Tcl variable to
9 C variable
10
12 #include <tcl.h>
13 int
15 Tcl_LinkVar(interp, varName, addr, type)
16 Tcl_UnlinkVar(interp, varName)
18 Tcl_UpdateLinkedVar(interp, varName)
20
22 Tcl_Interp *interp (in) Interpreter that contains varName.
23 Also used by Tcl_LinkVar to return
24 error messages.
25 const char *varName (in) Name of global variable.
27 char *addr (in) Address of C variable that is to be
29 linked to varName.
30 int type (in) Type of C variable. Must be one of
32 TCL_LINK_INT, TCL_LINK_UINT, │
33 TCL_LINK_CHAR, TCL_LINK_UCHAR, │
34 TCL_LINK_SHORT, TCL_LINK_USHORT, │
35 TCL_LINK_LONG, TCL_LINK_ULONG,
36 TCL_LINK_WIDE_INT, │
37 TCL_LINK_WIDE_UINT, TCL_LINK_FLOAT,
38 TCL_LINK_DOUBLE, TCL_LINK_BOOLEAN, or
39 TCL_LINK_STRING, optionally OR'ed
40 with TCL_LINK_READ_ONLY to make Tcl
41 variable read-only.
42_________________________________________________________________
43
46 Tcl_LinkVar uses variable traces to keep the Tcl variable named by var‐
47 Name in sync with the C variable at the address given by addr. When‐
48 ever the Tcl variable is read the value of the C variable will be
49 returned, and whenever the Tcl variable is written the C variable will
50 be updated to have the same value. Tcl_LinkVar normally returns
51 TCL_OK; if an error occurs while setting up the link (e.g. because
52 varName is the name of array) then TCL_ERROR is returned and the inter‐
53 preter's result contains an error message.
54 The type argument specifies the type of the C variable, and must have
56 one of the following values, optionally OR'ed with TCL_LINK_READ_ONLY:
57 TCL_LINK_INT
59 The C variable is of type int. Any value written into the Tcl
60 variable must have a proper integer form acceptable to Tcl_Get‐
61 IntFromObj; attempts to write non-integer values into varName
62 will be rejected with Tcl errors. │
63 TCL_LINK_UINT │
65 The C variable is of type unsigned int. Any value written into │
66 the Tcl variable must have a proper unsigned integer form │
67 acceptable to Tcl_GetWideIntFromObj and in the platform's │
68 defined range for the unsigned int type; attempts to write non- │
69 integer values (or values outside the range) into varName will │
70 be rejected with Tcl errors. │
71 TCL_LINK_CHAR │
73 The C variable is of type char. Any value written into the Tcl │
74 variable must have a proper integer form acceptable to Tcl_Get‐ │
75 IntFromObj and be in the range of the char datatype; attempts to │
76 write non-integer or out-of-range values into varName will be │
77 rejected with Tcl errors. │
78 TCL_LINK_UCHAR │
80 The C variable is of type unsigned char. Any value written into │
81 the Tcl variable must have a proper unsigned integer form │
82 acceptable to Tcl_GetIntFromObj and in the platform's defined │
83 range for the unsigned char type; attempts to write non-integer │
84 values (or values outside the range) into varName will be │
85 rejected with Tcl errors. │
86 TCL_LINK_SHORT │
88 The C variable is of type short. Any value written into the Tcl │
89 variable must have a proper integer form acceptable to Tcl_Get‐ │
90 IntFromObj and be in the range of the short datatype; attempts │
91 to write non-integer or out-of-range values into varName will be │
92 rejected with Tcl errors. │
93 TCL_LINK_USHORT │
95 The C variable is of type unsigned short. Any value written │
96 into the Tcl variable must have a proper unsigned integer form │
97 acceptable to Tcl_GetIntFromObj and in the platform's defined │
98 range for the unsigned short type; attempts to write non-integer │
99 values (or values outside the range) into varName will be │
100 rejected with Tcl errors. │
101 TCL_LINK_LONG │
103 The C variable is of type long. Any value written into the Tcl │
104 variable must have a proper integer form acceptable to Tcl_Get‐ │
105 LongFromObj; attempts to write non-integer or out-of-range val‐ │
106 ues into varName will be rejected with Tcl errors. │
107 TCL_LINK_ULONG │
109 The C variable is of type unsigned long. Any value written into │
110 the Tcl variable must have a proper unsigned integer form │
111 acceptable to Tcl_GetWideIntFromObj and in the platform's │
112 defined range for the unsigned long type; attempts to write non- │
113 integer values (or values outside the range) into varName will │
114 be rejected with Tcl errors.
115 TCL_LINK_DOUBLE
117 The C variable is of type double. Any value written into the
118 Tcl variable must have a proper real form acceptable to Tcl_Get‐
119 DoubleFromObj; attempts to write non-real values into varName
120 will be rejected with Tcl errors. │
121 TCL_LINK_FLOAT │
123 The C variable is of type float. Any value written into the Tcl │
124 variable must have a proper real form acceptable to Tcl_GetDou‐ │
125 bleFromObj and must be within the range acceptable for a float; │
126 attempts to write non-real values (or values outside the range) │
127 into varName will be rejected with Tcl errors.
128 TCL_LINK_WIDE_INT
130 The C variable is of type Tcl_WideInt (which is an integer type
131 at least 64-bits wide on all platforms that can support it.)
132 Any value written into the Tcl variable must have a proper inte‐
133 ger form acceptable to Tcl_GetWideIntFromObj; attempts to write
134 non-integer values into varName will be rejected with Tcl
135 errors. │
136 TCL_LINK_WIDE_UINT │
138 The C variable is of type Tcl_WideUInt (which is an unsigned │
139 integer type at least 64-bits wide on all platforms that can │
140 support it.) Any value written into the Tcl variable must have │
141 a proper unsigned integer form acceptable to Tcl_GetWideIntFro‐ │
142 mObj (it will be cast to unsigned); attempts to write non-inte‐ │
143 ger values into varName will be rejected with Tcl errors.
144 TCL_LINK_BOOLEAN
146 The C variable is of type int. If its value is zero then it
147 will read from Tcl as “0”; otherwise it will read from Tcl as
148 “1”. Whenever varName is modified, the C variable will be set
149 to a 0 or 1 value. Any value written into the Tcl variable must
150 have a proper boolean form acceptable to Tcl_GetBooleanFromObj;
151 attempts to write non-boolean values into varName will be
152 rejected with Tcl errors.
153 TCL_LINK_STRING
155 The C variable is of type char *. If its value is not NULL then
156 it must be a pointer to a string allocated with Tcl_Alloc or
157 ckalloc. Whenever the Tcl variable is modified the current C
158 string will be freed and new memory will be allocated to hold a
159 copy of the variable's new value. If the C variable contains a
160 NULL pointer then the Tcl variable will read as “NULL”.
161 If the TCL_LINK_READ_ONLY flag is present in type then the variable
163 will be read-only from Tcl, so that its value can only be changed by
164 modifying the C variable. Attempts to write the variable from Tcl will
165 be rejected with errors.
166 Tcl_UnlinkVar removes the link previously set up for the variable given
168 by varName. If there does not exist a link for varName then the proce‐
169 dure has no effect.
170 Tcl_UpdateLinkedVar may be invoked after the C variable has changed to
172 force the Tcl variable to be updated immediately. In many cases this
173 procedure is not needed, since any attempt to read the Tcl variable
174 will return the latest value of the C variable. However, if a trace
175 has been set on the Tcl variable (such as a Tk widget that wishes to
176 display the value of the variable), the trace will not trigger when the
177 C variable has changed. Tcl_UpdateLinkedVar ensures that any traces on
178 the Tcl variable are invoked.
179
182 boolean, integer, link, read-only, real, string, traces, variable
183Tcl 7.5 Tcl_LinkVar(3)