Manual Reference Pages - TCL_EVALOBJEX (3)
Tcl_EvalObjEx, Tcl_EvalFile, Tcl_EvalObjv, Tcl_Eval, Tcl_EvalEx, Tcl_GlobalEval, Tcl_GlobalEvalObj, Tcl_VarEval, Tcl_VarEvalVA - execute Tcl scripts
Tcl_EvalObjEx(interp, objPtr, flags)
Tcl_EvalObjv(interp, objc, objv, flags)
Tcl_EvalEx(interp, script, numBytes, flags)
Tcl_VarEval(interp, part, part, ... (char *) NULL)
Tcl_Interp *interp (in)
Interpreter in which to execute the script. The interpreters 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 *fileName (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 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.
const char *script (in)
Points to first byte of script to execute (null-terminated and UTF-8).
char *part (in)
String forming part of a Tcl script.
va_list argList (in)
An argument list which must have been initialized using
va_start, and cleared using va_end.
The procedures described here are invoked to execute Tcl scripts in
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 interps
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
If the file could not be read then a Tcl error is returned to describe
why the file could not be read.
The eofchar for files is
(^Z) for all platforms. If you require a
in code for string comparison, you can use
which will be safely substituted by the Tcl interpreter into
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.
The caller of Tcl_EvalObjv has to manage the reference count of the
elements of objv, insuring that the objects are valid until
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 converted by
Tcl_ExternalToUtfDString or Tcl_ExternalToUtf when it is known
to possibly contain upper ASCII characters whose 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 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 completion 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
does not 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
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.
Any ORed combination of the following values may be used for the
flags argument to procedures such as Tcl_EvalObjEx:
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 immediately, so the
bytecodes will not be reused in a future execution. In this case,
it is faster to execute the script directly.
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).
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_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 interps 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.
execute, file, global, object, result, script
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