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Tcl Library Procedures Tcl_Eval(3TCL)

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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

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) ||

Tcl_Obj *objPtr (in) ||

A Tcl object containing | the script to execute. | int flags (in) || ORed combination of flag | Tcl Last change: 8.1 1

Tcl Library Procedures Tcl_Eval(3TCL)

bits that specify addi- |

tional options. |

TCL_EVAL_GLOBAL and |

TCL_EVAL_DIRECT are |

currently supported. | CONST 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. | 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 initial- |

ised using |

TCL_VARARGS_START, and |

cleared using va_end. |

_________________________________________________________________ |

Tcl Last change: 8.1 2

Tcl Library Procedures Tcl_Eval(3TCL)

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, or possibly some other integer value originat- |

ing 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 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. The eofchar for files is '\32' (^Z) for all plat- |

forms. If you require a ``^Z'' in code for string com- |

parison, 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 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 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 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 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 ver-

sions 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

Tcl Last change: 8.1 3

Tcl Library Procedures Tcl_Eval(3TCL)

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 Tcl Last change: 8.1 4

Tcl Library Procedures Tcl_Eval(3TCL)

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

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

_______________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tcl-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.1 5