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Tcl_Cancel(3) Tcl Library Procedures Tcl_Cancel(3)
______________________________________________________________________________
NAME
Tcl_CancelEval, Tcl_Canceled - cancel Tcl scripts
SYNOPSIS
#include <tcl.h>
int
Tcl_CancelEval(interp, clientData, flags)
int
Tcl_Canceled(interp, flags)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter in which to can‐
cel the script.
int flags (in) ORed combination of flag bits
that specify additional
options. For Tcl_CancelEval,
only TCL_CANCEL_UNWIND is
currently supported. For
Tcl_Canceled, only
TCL_LEAVE_ERR_MSG and
TCL_CANCEL_UNWIND are cur‐
rently supported.
ClientData clientData (in) Currently, reserved for
future use. It should be set
to NULL.
_________________________________________________________________
DESCRIPTION
Tcl_CancelEval cancels or unwinds the script in progress soon after the
next invocation of asynchronous handlers, causing TCL_ERROR to be the
return code for that script. This function is thread-safe and may be
called from any thread in the process.
Tcl_Canceled checks if the script in progress has been canceled and
returns TCL_ERROR if it has. Otherwise, TCL_OK is returned. Exten‐
sions can use this function to check to see if they should abort a long
running command. This function is thread sensitive and may only be
called from the thread the interpreter was created in.
FLAG BITS
Any ORed combination of the following values may be used for the flags
argument to procedures such as Tcl_CancelEval:
TCL_CANCEL_UNWIND This flag is used by Tcl_CancelEval and Tcl_Can‐
celed. For Tcl_CancelEval, if this flag is set,
the script in progress is canceled and the eval‐
uation stack for the interpreter is unwound.
For Tcl_Canceled, if this flag is set, the
script in progress is considered to be canceled
only if the evaluation stack for the interpreter
is being unwound.
TCL_LEAVE_ERR_MSG This flag is only used by Tcl_Canceled; it is
ignored by other procedures. If an error is
returned and this bit is set in flags, then an
error message will be left in the interpreter's
result, where it can be retrieved with Tcl_GetO‐
bjResult or Tcl_GetStringResult. If this flag
bit is not set then no error message is left and
the interpreter's result will not be modified.
SEE ALSO
TIP 285
KEYWORDS
cancel, unwind
Tcl 8.6 Tcl_Cancel(3)
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