MAN sezione 3 - Torna all'indice
MAN PAGE: Tcl_Eval(3)Contents
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Tcl_Eval, Tcl_VarEval, Tcl_EvalFile, Tcl_GlobalEval - exe
cute Tcl commands
#include <tcl.h>
int
Tcl_Eval(interp, cmd)
int
Tcl_VarEval(interp, string, string, ... (char *) NULL)
int
Tcl_EvalFile(interp, fileName)
int
Tcl_GlobalEval(interp, cmd)
Tcl_Interp *interp (in) Interpreter in which
to execute the com
mand. A string result
will be stored in
interp->result.
char *cmd (in) Command (or sequence
of commands) to exe
cute. Must be in
writable memory
(Tcl_Eval makes tempo
rary modifications to
the command).
char *string (in) String forming part of
Tcl command.
char *fileName (in) Name of file contain
ing Tcl command
string.
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All four of these procedures execute Tcl commands.
Tcl_Eval is the core procedure and is used by all the oth
ers. It executes the commands in the script held by cmd
until either an error occurs or it reaches the end of the
script.
Note that Tcl_Eval and Tcl_GlobalEval have been largely
replaced by the object-based procedures Tcl_EvalObj and
Tcl_GlobalEvalObj. Those object-based procedures evaluate
a script held in a Tcl object instead of a string. The
object argument can retain the bytecode instructions for
the script and so avoid reparsing the script each time it
is executed. Tcl_Eval is implemented using Tcl_EvalObj
but is slower because it must reparse the script each time
since there is no object to retain the bytecode instruc
tions.
The return value from Tcl_Eval is one of the Tcl return
codes TCL_OK, TCL_ERROR, TCL_RETURN, TCL_BREAK, or
TCL_CONTINUE, and interp->result will point to a string
with additional information (a result value or error mes
sage). If an error occurs during compilation, this return
information describes the error. Otherwise, this return
information corresponds to the last command executed from
cmd.
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 usual fashion for Tcl commands. The
last argument to Tcl_VarEval must be NULL to indicate the
end of arguments.
Tcl_EvalFile reads the file given by fileName and evalu
ates its contents as a Tcl command by calling Tcl_Eval.
It returns a standard Tcl result that reflects the result
of evaluating the file. If the file couldn't be read then
a Tcl error is returned to describe why the file couldn't
be read.
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_Eval 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_Eval keeps track of how many nested Tcl_Eval invoca
tions 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_Eval invocation for interp,
it converts the return code to TCL_ERROR and sets
interp->result to point to an error message indicating
that the return, break, or continue command was invoked in
an inappropriate place. This means that top-level appli
cations should never see a return code from Tcl_Eval other
then TCL_OK or TCL_ERROR. Tcl_EvalObj, Tcl_GlobalEvalObj
command, execute, file, global, object, object result,
variable
Tcl 7.0 3 |
