SetResult

Tcl_SetResult(3)            Tcl Library Procedures            Tcl_SetResult(3)



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NAME
       Tcl_SetResult, Tcl_AppendResult, Tcl_AppendElement, Tcl_ResetResult -
       manipulate Tcl result string

SYNOPSIS
       #include <tcl.h>

       Tcl_SetResult(interp, string, freeProc)

       Tcl_AppendResult(interp, string, string, ... , (char *) NULL)

       Tcl_AppendElement(interp, string)

       Tcl_ResetResult(interp)

       Tcl_FreeResult(interp)

ARGUMENTS
       Tcl_Interp     *interp    (out)     Interpreter whose result is to be
                                           modified.

       char           *string    (in)      String value to become result for
                                           interp or to be appended to
                                           existing result.

       Tcl_FreeProc   *freeProc  (in)      Address of procedure to call to
                                           release storage at string, or
                                           TCL_STATIC, TCL_DYNAMIC, or
                                           TCL_VOLATILE.
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DESCRIPTION
       The procedures described here are utilities for setting the
       result/error string in a Tcl interpreter.

       Tcl_SetResult arranges for string to be the return string for the
       current Tcl command in interp, replacing any existing result.  If
       freeProc is TCL_STATIC it means that string refers to an area of static
       storage that is guaranteed not to be modified until at least the next
       call to Tcl_Eval.  If freeProc is TCL_DYNAMIC it means that string was  │
       allocated with a call to Tcl_Alloc and is now the property of the Tcl   │
       system.  Tcl_SetResult will arrange for the string's storage to be      │
       released by calling Tcl_Free when it is no longer needed.  If freeProc
       is TCL_VOLATILE it means that string points to an area of memory that
       is likely to be overwritten when Tcl_SetResult returns (e.g. it points
       to something in a stack frame).  In this case Tcl_SetResult will make a
       copy of the string in dynamically allocated storage and arrange for the
       copy to be the return string for the current Tcl command.

       If freeProc isn't one of the values TCL_STATIC, TCL_DYNAMIC, and
       TCL_VOLATILE, then it is the address of a procedure that Tcl should
       call to free the string.  This allows applications to use non-standard
       storage allocators.  When Tcl no longer needs the storage for the
       string, it will call freeProc.  FreeProc should have arguments and
       result that match the type Tcl_FreeProc:
              typedef void Tcl_FreeProc(char *blockPtr);
       When freeProc is called, its blockPtr will be set to the value of
       string passed to Tcl_SetResult.

       If string is NULL, then freeProc is ignored and Tcl_SetResult re-
       initializes interp's result to point to the pre-allocated result area,
       with an empty string in the result area.

       If Tcl_SetResult is called at a time when interp holds a result,
       Tcl_SetResult does whatever is necessary to dispose of the old result
       (see the Tcl_Interp manual entry for details on this).

       Tcl_AppendResult makes it easy to build up Tcl results in pieces.  It
       takes each of its string arguments and appends them in order to the
       current result associated with interp.  If the result is in its
       initialized empty state (e.g. a command procedure was just invoked or
       Tcl_ResetResult was just called), then Tcl_AppendResult sets the result
       to the concatenation of its string arguments.  Tcl_AppendResult may be
       called repeatedly as additional pieces of the result are produced.
       Tcl_AppendResult takes care of all the storage management issues
       associated with managing interp's result, such as allocating a larger
       result area if necessary.  Any number of string arguments may be passed
       in a single call;  the last argument in the list must be a NULL
       pointer.

       Tcl_AppendElement is similar to Tcl_AppendResult in that it allows
       results to be built up in pieces.  However, Tcl_AppendElement takes
       only a single string argument and it appends that argument to the
       current result as a proper Tcl list element.  Tcl_AppendElement adds
       backslashes or braces if necessary to ensure that interp's result can
       be parsed as a list and that string will be extracted as a single
       element.  Under normal conditions, Tcl_AppendElement will add a space
       character to interp's result just before adding the new list element,
       so that the list elements in the result are properly separated.
       However if the new list element is the first in a list or sub-list
       (i.e. interp's current result is empty, or consists of the single
       character ``{'', or ends in the characters `` {'') then no space is
       added.

       Tcl_ResetResult clears the result for interp, freeing the memory
       associated with it if the current result was dynamically allocated.  It
       leaves the result in its normal initialized state with interp->result
       pointing to a static buffer containing TCL_RESULT_SIZE characters, of
       which the first character is zero.  Tcl_ResetResult also clears the
       error state managed by Tcl_AddErrorInfo and Tcl_SetErrorCode.

       Tcl_FreeResult is a macro that performs part of the work of
       Tcl_ResetResult.  It frees up the memory associated with interp's
       result and sets interp->freeProc to zero, but it doesn't change
       interp->result or clear error state.  Tcl_FreeResult is most commonly
       used when a procedure is about to replace one result value with
       another.


SEE ALSO
       Tcl_AddErrorInfo, Tcl_SetErrorCode, Tcl_Interp


KEYWORDS
       append, command, element, list, result, return value, interpreter



Tcl                                   7.5                     Tcl_SetResult(3)