Tcl_Eval(3) Tcl Library Procedures Tcl_Eval(3)
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NAME
Tcl_EvalObjEx, Tcl_EvalFile, Tcl_EvalObjv, Tcl_Eval, Tcl_EvalEx, Tcl_GlobalEval, Tcl_GlobalEvalObj,
Tcl_VarEval, Tcl_VarEvalVA - execute Tcl scripts
SYNOPSIS
#include <tcl.h>
int |
Tcl_EvalObjEx(interp, objPtr, flags) |
int |
Tcl_EvalFile(interp, fileName) |
int |
Tcl_EvalObjv(interp, objc, objv, flags) |
int |
Tcl_Eval(interp, script) |
int |
Tcl_EvalEx(interp, script, numBytes, flags) |
int |
Tcl_GlobalEval(interp, script) |
int |
Tcl_GlobalEvalObj(interp, objPtr) |
int |
Tcl_VarEval(interp, string, string, ... (char *) NULL) |
int |
Tcl_VarEvalVA(interp, argList) |
ARGUMENTS |
Tcl_Interp *interp (in) ||
Interpreter in which to execute the script. The interpreter's |
result is modified to hold the result or error message from the |
script. |
Tcl_Obj *objPtr (in) ||
A Tcl object containing the script to execute. |
int flags (in) ||
ORed combination of flag bits that specify additional options. |
TCL_EVAL_GLOBAL and TCL_EVAL_DIRECT are currently supported. |
CONST char *file- |
Name (in) | |
Name of a file containing a Tcl script. |
int objc (in) ||
The number of objects in the array pointed to by objPtr; this is |
also the number of words in the command. |
Tcl_Obj **objv (in) ||
Points to an array of pointers to objects; each object holds the |
value of a single word in the command to execute. |
int num- |
Bytes (in) | |
The number of bytes in script, not including any null terminating |
character. If -1, then all characters up to the first null byte |
are used. |
CONST |
char *script (in) | |
Points to first byte of script to execute (null-terminated and |
UTF-8). |
char *string (in) ||
String forming part of a Tcl script. |
va_list argList (in) ||
An argument list which must have been initialised using |
TCL_VARARGS_START, and cleared using va_end. |
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DESCRIPTION |
The procedures described here are invoked to execute Tcl scripts in various forms. Tcl_EvalObjEx is |
the core procedure and is used by many of the others. It executes the commands in the script stored |
in objPtr until either an error occurs or the end of the script is reached. If this is the first |
time objPtr has been executed, its commands are compiled into bytecode instructions which are then |
executed. The bytecodes are saved in objPtr so that the compilation step can be skipped if the |
object is evaluated again in the future. |
The return value from Tcl_EvalObjEx (and all the other procedures described here) is a Tcl completion |
code with one of the values TCL_OK, TCL_ERROR, TCL_RETURN, TCL_BREAK, or TCL_CONTINUE, or possibly |
some other integer value originating in an extension. In addition, a result value or error message |
is left in interp's result; it can be retrieved using Tcl_GetObjResult. |
Tcl_EvalFile reads the file given by fileName and evaluates its contents as a Tcl script. It returns |
the same information as Tcl_EvalObjEx. If the file couldn't be read then a Tcl error is returned to |
describe why the file couldn't be read. The eofchar for files is '\32' (^Z) for all platforms. If |
you require a ``^Z'' in code for string comparison, you can use ``\032'' or ``\u001a'', which will be |
safely substituted by the Tcl interpreter into ``^Z''.
Tcl_EvalObjv executes a single pre-parsed command instead of a script. The objc and objv arguments
contain the values of the words for the Tcl command, one word in each object in objv. Tcl_EvalObjv
evaluates the command and returns a completion code and result just like Tcl_EvalObjEx.
Tcl_Eval is similar to Tcl_EvalObjEx except that the script to be executed is supplied as a string
instead of an object and no compilation occurs. The string should be a proper UTF-8 string as con-verted converted
verted by Tcl_ExternalToUtfDString or Tcl_ExternalToUtf when it is known to possibly contain upper
ASCII characters who's possible combinations might be a UTF-8 special code. The string is parsed and
executed directly (using Tcl_EvalObjv) instead of compiling it and executing the bytecodes. In situ-ations situations
ations where it is known that the script will never be executed again, Tcl_Eval may be faster than
Tcl_EvalObjEx.
Tcl_Eval returns a completion code and result just like Tcl_EvalObjEx. Note: for backward compati-bility compatibility
bility with versions before Tcl 8.0, Tcl_Eval copies the object result in interp to interp->result
(use is deprecated) where it can be accessed directly.
This makes Tcl_Eval somewhat slower than Tcl_EvalEx, which doesn't do the copy.
Tcl_EvalEx is an extended version of Tcl_Eval that takes additional arguments numBytes and flags.
For the efficiency reason given above, Tcl_EvalEx is generally preferred over Tcl_Eval.
Tcl_GlobalEval and Tcl_GlobalEvalObj are older procedures that are now deprecated. They are similar
to Tcl_EvalEx and Tcl_EvalObjEx except that the script is evaluated in the global namespace and its
variable context consists of global variables only (it ignores any Tcl procedures that are active).
These functions are equivalent to using the TCL_EVAL_GLOBAL flag (see below).
Tcl_VarEval takes any number of string arguments of any length, concatenates them into a single
string, then calls Tcl_Eval to execute that string as a Tcl command. It returns the result of the
command and also modifies interp->result in the same way as Tcl_Eval. The last argument to
Tcl_VarEval must be NULL to indicate the end of arguments. Tcl_VarEval is now deprecated.
Tcl_VarEvalVA is the same as Tcl_VarEval except that instead of taking a variable number of arguments
it takes an argument list. Like Tcl_VarEval, Tcl_VarEvalVA is deprecated.
FLAG BITS
Any ORed combination of the following values may be used for the flags argument to procedures such as
Tcl_EvalObjEx:
TCL_EVAL_DIRECT This flag is only used by Tcl_EvalObjEx; it is ignored by other procedures.
If this flag bit is set, the script is not compiled to bytecodes; instead it
is executed directly as is done by Tcl_EvalEx. The TCL_EVAL_DIRECT flag is
useful in situations where the contents of an object are going to change imme-diately, immediately,
diately, so the bytecodes won't be reused in a future execution. In this
case, it's faster to execute the script directly.
TCL_EVAL_GLOBAL If this flag is set, the script is processed at global level. This means that
it is evaluated in the global namespace and its variable context consists of
global variables only (it ignores any Tcl procedures at are active).
MISCELLANEOUS DETAILS
During the processing of a Tcl command it is legal to make nested calls to evaluate other commands
(this is how procedures and some control structures are implemented). If a code other than TCL_OK is
returned from a nested Tcl_EvalObjEx invocation, then the caller should normally return immediately,
passing that same return code back to its caller, and so on until the top-level application is
reached. A few commands, like for, will check for certain return codes, like TCL_BREAK and TCL_CON-TINUE, TCL_CONTINUE,
TINUE, and process them specially without returning.
Tcl_EvalObjEx keeps track of how many nested Tcl_EvalObjEx invocations are in progress for interp.
If a code of TCL_RETURN, TCL_BREAK, or TCL_CONTINUE is about to be returned from the topmost
Tcl_EvalObjEx invocation for interp, it converts the return code to TCL_ERROR and sets interp's
result to an error message indicating that the return, break, or continue command was invoked in an
inappropriate place. This means that top-level applications should never see a return code from
Tcl_EvalObjEx other then TCL_OK or TCL_ERROR.
KEYWORDS
execute, file, global, object, result, script
Tcl 8.1 Tcl_Eval(3)
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