1Tcl_Eval(3) Tcl Library Procedures Tcl_Eval(3)
2______________________________________________________________________________
6
8 Tcl_EvalObjEx, Tcl_EvalFile, Tcl_EvalObjv, Tcl_Eval, Tcl_EvalEx,
9 Tcl_GlobalEval, Tcl_GlobalEvalObj, Tcl_VarEval, Tcl_VarEvalVA - execute
10 Tcl scripts
11
13 #include <tcl.h>
14 int
16 Tcl_EvalObjEx(interp, objPtr, flags)
17 int
19 Tcl_EvalFile(interp, fileName)
20 int
22 Tcl_EvalObjv(interp, objc, objv, flags)
23 int
25 Tcl_Eval(interp, script)
26 int
28 Tcl_EvalEx(interp, script, numBytes, flags)
29 int
31 Tcl_GlobalEval(interp, script)
32 int
34 Tcl_GlobalEvalObj(interp, objPtr)
35 int
37 Tcl_VarEval(interp, part, part, ... (char *) NULL)
38 int
40 Tcl_VarEvalVA(interp, argList)
41
43 Tcl_Interp *interp (in) Interpreter in which to execute the
44 script. The interpreter's result is
45 modified to hold the result or error
46 message from the script.
47 Tcl_Obj *objPtr (in) A Tcl value containing the script to
49 execute.
50 int flags (in) ORed combination of flag bits that
52 specify additional options.
53 TCL_EVAL_GLOBAL and TCL_EVAL_DIRECT
54 are currently supported.
55 const char *fileName (in) Name of a file containing a Tcl
57 script.
58 int objc (in) The number of values in the array
60 pointed to by objPtr; this is also
61 the number of words in the command.
62 Tcl_Obj **objv (in) Points to an array of pointers to
64 values; each value holds the value
65 of a single word in the command to
66 execute.
67 int numBytes (in) The number of bytes in script, not
69 including any null terminating char‐
70 acter. If -1, then all characters
71 up to the first null byte are used.
72 const char *script (in) Points to first byte of script to
74 execute (null-terminated and UTF-8).
75 char *part (in) String forming part of a Tcl script.
77 va_list argList (in) An argument list which must have
79 been initialized using va_start, and
80 cleared using va_end.
81______________________________________________________________________________
82
85 The procedures described here are invoked to execute Tcl scripts in
86 various forms. Tcl_EvalObjEx is the core procedure and is used by many
87 of the others. It executes the commands in the script stored in objPtr
88 until either an error occurs or the end of the script is reached. If
89 this is the first time objPtr has been executed, its commands are com‐
90 piled into bytecode instructions which are then executed. The byte‐
91 codes are saved in objPtr so that the compilation step can be skipped
92 if the value is evaluated again in the future.
93 The return value from Tcl_EvalObjEx (and all the other procedures
95 described here) is a Tcl completion code with one of the values TCL_OK,
96 TCL_ERROR, TCL_RETURN, TCL_BREAK, or TCL_CONTINUE, or possibly some
97 other integer value originating in an extension. In addition, a result
98 value or error message is left in interp's result; it can be retrieved
99 using Tcl_GetObjResult.
100 Tcl_EvalFile reads the file given by fileName and evaluates its con‐
102 tents as a Tcl script. It returns the same information as Tcl_EvalOb‐
103 jEx. If the file could not be read then a Tcl error is returned to
104 describe why the file could not be read. The eofchar for files is
105 “\32” (^Z) for all platforms. If you require a “^Z” in code for string
106 comparison, you can use “\032” or “\u001a”, which will be safely sub‐
107 stituted by the Tcl interpreter into “^Z”.
108 Tcl_EvalObjv executes a single pre-parsed command instead of a script.
110 The objc and objv arguments contain the values of the words for the Tcl
111 command, one word in each value in objv. Tcl_EvalObjv evaluates the
112 command and returns a completion code and result just like Tcl_EvalOb‐
113 jEx. The caller of Tcl_EvalObjv has to manage the reference count of
114 the elements of objv, insuring that the values are valid until
115 Tcl_EvalObjv returns.
116 Tcl_Eval is similar to Tcl_EvalObjEx except that the script to be exe‐
118 cuted is supplied as a string instead of a value and no compilation
119 occurs. The string should be a proper UTF-8 string as converted by
120 Tcl_ExternalToUtfDString or Tcl_ExternalToUtf when it is known to pos‐
121 sibly contain upper ASCII characters whose possible combinations might
122 be a UTF-8 special code. The string is parsed and executed directly
123 (using Tcl_EvalObjv) instead of compiling it and executing the byte‐
124 codes. In situations where it is known that the script will never be
125 executed again, Tcl_Eval may be faster than Tcl_EvalObjEx.
126 Tcl_Eval returns a completion code and result just like Tcl_EvalObjEx.
127 Note: for backward compatibility with versions before Tcl 8.0, Tcl_Eval
128 copies the value result in interp to interp->result (use is deprecated)
129 where it can be accessed directly.
130 This makes Tcl_Eval somewhat slower than Tcl_EvalEx, which does not do
131 the copy.
132 Tcl_EvalEx is an extended version of Tcl_Eval that takes additional
134 arguments numBytes and flags. For the efficiency reason given above,
135 Tcl_EvalEx is generally preferred over Tcl_Eval.
136 Tcl_GlobalEval and Tcl_GlobalEvalObj are older procedures that are now
138 deprecated. They are similar to Tcl_EvalEx and Tcl_EvalObjEx except
139 that the script is evaluated in the global namespace and its variable
140 context consists of global variables only (it ignores any Tcl proce‐
141 dures that are active). These functions are equivalent to using the
142 TCL_EVAL_GLOBAL flag (see below).
143 Tcl_VarEval takes any number of string arguments of any length, con‐
145 catenates them into a single string, then calls Tcl_Eval to execute
146 that string as a Tcl command. It returns the result of the command and
147 also modifies interp->result in the same way as Tcl_Eval. The last
148 argument to Tcl_VarEval must be NULL to indicate the end of arguments.
149 Tcl_VarEval is now deprecated.
150 Tcl_VarEvalVA is the same as Tcl_VarEval except that instead of taking
152 a variable number of arguments it takes an argument list. Like
153 Tcl_VarEval, Tcl_VarEvalVA is deprecated.
154
157 Any ORed combination of the following values may be used for the flags
158 argument to procedures such as Tcl_EvalObjEx:
159 TCL_EVAL_DIRECT This flag is only used by Tcl_EvalObjEx; it is
161 ignored by other procedures. If this flag bit
162 is set, the script is not compiled to bytecodes;
163 instead it is executed directly as is done by
164 Tcl_EvalEx. The TCL_EVAL_DIRECT flag is useful
165 in situations where the contents of a value are
166 going to change immediately, so the bytecodes
167 will not be reused in a future execution. In
168 this case, it is faster to execute the script
169 directly.
170 TCL_EVAL_GLOBAL If this flag is set, the script is processed at
172 global level. This means that it is evaluated
173 in the global namespace and its variable context
174 consists of global variables only (it ignores
175 any Tcl procedures that are active).
176
179 During the processing of a Tcl command it is legal to make nested calls
180 to evaluate other commands (this is how procedures and some control
181 structures are implemented). If a code other than TCL_OK is returned
182 from a nested Tcl_EvalObjEx invocation, then the caller should normally
183 return immediately, passing that same return code back to its caller,
184 and so on until the top-level application is reached. A few commands,
185 like for, will check for certain return codes, like TCL_BREAK and
186 TCL_CONTINUE, and process them specially without returning.
187 Tcl_EvalObjEx keeps track of how many nested Tcl_EvalObjEx invocations
189 are in progress for interp. If a code of TCL_RETURN, TCL_BREAK, or
190 TCL_CONTINUE is about to be returned from the topmost Tcl_EvalObjEx
191 invocation for interp, it converts the return code to TCL_ERROR and
192 sets interp's result to an error message indicating that the return,
193 break, or continue command was invoked in an inappropriate place. This
194 means that top-level applications should never see a return code from
195 Tcl_EvalObjEx other than TCL_OK or TCL_ERROR.
196
199 execute, file, global, result, script, value
200Tcl 8.1 Tcl_Eval(3)