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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, flags) |
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 addi- |
tional options. |
TCL_EVAL_GLOBAL and |
TCL_EVAL_DIRECT are |
currently supported. |
char *fileName (in) ||
Name of a file contain- |
ing 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 exe- |
cute. |
int numBytes (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. |
char *script (in) ||
Points to first byte of |
script to execute. This |
script must be in writ- |
able memory: temporary |
modifications are made |
to it during parsing. |
char *string (in) ||
String forming part of a |
Tcl script. |
va_list argList (in) ||
An argument list which |
must have been initial- |
ised using |
TCL_VARARGS_START, and |
cleared using va_end. |
_________________________________________________________________ |
DESCRIPTION |
The procedures described here are invoked to execute Tcl |
scripts in various forms. Tcl_EvalObjEx is the core pro- |
cedure 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 pro- |
cedures described here) is a Tcl completion code with one of |
the values TCL_OK, TCL_ERROR, TCL_RETURN, TCL_BREAK, or |
TCL_CONTINUE. 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 informa- |
tion 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. |
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 com- |
pletion 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 is parsed and exe- |
cuted directly (using Tcl_EvalObjv) instead of compiling it |
and executing the bytecodes. In situations where it is |
known that the script will never be executed again, Tcl_Eval |
may be faster than Tcl_EvalObjEx. Tcl_Eval returns a com- |
pletion code and result just like Tcl_EvalObjEx. Note: for |
backward compatibility 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 argu- |
ment 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 immedi- |
ately, 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 pro- |
cedures 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_CONTINUE, 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 inap- |
propriate 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
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