Tcl_Eval(3) Tcl Library Procedures Tcl_Eval(3) ______________________________________________________________________________
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, part, part, ... (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 value containing the script to
execute.
int flags (in) OR'ed 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 values in the array
pointed to by objv; this is also the
number of words in the command.
Tcl_Obj **objv (in) Points to an array of pointers to
values; each value 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).
const 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.
______________________________________________________________________________
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 value 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 could not be read then a Tcl error is
returned to describe why the file could not 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 preparsed command instead of a script.
The objc and objv arguments contain the values of the words for the Tcl
command, one word in each value 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 values are valid until
Tcl_EvalObjv returns.
Tcl_Eval is similar to Tcl_EvalObjEx except that the script to be
executed is supplied as a string instead of a value 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 value 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 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_VarEvalVA is the same as Tcl_VarEval except that instead of taking
a variable number of arguments it takes an argument list.
Tcl_VarEvalVA is now deprecated.
FLAG BITS
Any OR'ed 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 a value 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.
TCL_EVAL_GLOBAL If this flag is set, the script is evaluated in
the global namespace instead of the current
namespace and its variable context consists of
global variables only (it ignores any Tcl
procedures that 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_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 inappropriate place. This
means that top-level applications should never see a return code from
Tcl_EvalObjEx other than TCL_OK or TCL_ERROR.
KEYWORDS
execute, file, global, result, script, value
Tcl 8.1 Tcl_Eval(3)
tcl 8.6.14 - Generated Sun Mar 3 16:33:51 CST 2024