diff --git a/hawk/lib/fnc.c b/hawk/lib/fnc.c
index 21e6c84d..7c6ba4ec 100644
--- a/hawk/lib/fnc.c
+++ b/hawk/lib/fnc.c
@@ -405,7 +405,7 @@ static int fnc_close (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 		}
 	}
 
-	n = hawk_rtx_closeio (rtx, name, opt);
+	n = hawk_rtx_closeio(rtx, name, opt);
 	/* failure to close is not a critical error. instead, that is
 	 * flagged by the return value of close(). 
 	if (n <= -1 && rtx->errinf.num != HAWK_EIONMNF)
@@ -430,7 +430,7 @@ static int flush_io (hawk_rtx_t* rtx, int rio, const hawk_ooch_t* name, int n)
 {
 	int n2;
 
-	if (rtx->rio.handler[rio] != HAWK_NULL)
+	if (rtx->rio.handler[rio])
 	{
 		n2 = hawk_rtx_flushio(rtx, rio, name);
 		if (n2 <= -1)
@@ -484,8 +484,8 @@ static int fnc_fflush (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 	{
 		hawk_ooch_t* ptr, * end;
 
-		a0 = hawk_rtx_getarg (rtx, 0);
-		str0 = hawk_rtx_getvaloocstr (rtx, a0, &len0);
+		a0 = hawk_rtx_getarg(rtx, 0);
+		str0 = hawk_rtx_getvaloocstr(rtx, a0, &len0);
 		if (str0 == HAWK_NULL) return -1;
 
 		/* the target name contains a null character.
@@ -521,21 +521,13 @@ static int fnc_fflush (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 		 *  }
 		 */
 
-		n = flush_io (
-			rtx, HAWK_OUT_FILE, 
-			((len0 == 0)? HAWK_NULL: str0), 1);
+		n = flush_io(rtx, HAWK_OUT_FILE, ((len0 == 0)? HAWK_NULL: str0), 1);
 		/*if (n == -99) return -1;*/
-		n = flush_io (
-			rtx, HAWK_OUT_APFILE, 
-			((len0 == 0)? HAWK_NULL: str0), n);
+		n = flush_io(rtx, HAWK_OUT_APFILE, ((len0 == 0)? HAWK_NULL: str0), n);
 		/*if (n == -99) return -1;*/
-		n = flush_io (
-			rtx, HAWK_OUT_PIPE,
-			((len0 == 0)? HAWK_NULL: str0), n);
+		n = flush_io(rtx, HAWK_OUT_PIPE, ((len0 == 0)? HAWK_NULL: str0), n);
 		/*if (n == -99) return -1;*/
-		n = flush_io (
-			rtx, HAWK_OUT_RWPIPE,
-			((len0 == 0)? HAWK_NULL: str0), n);
+		n = flush_io(rtx, HAWK_OUT_RWPIPE, ((len0 == 0)? HAWK_NULL: str0), n);
 		/*if (n == -99) return -1;*/
 
 		/* if n remains 1, no io handlers have been defined for
diff --git a/hawk/lib/rio-prv.h b/hawk/lib/rio-prv.h
index bb44eacf..c3ee06cf 100644
--- a/hawk/lib/rio-prv.h
+++ b/hawk/lib/rio-prv.h
@@ -32,41 +32,42 @@ extern "C" {
 #endif
 
 int hawk_rtx_readio (
-	hawk_rtx_t* run, int in_type, 
+	hawk_rtx_t* rtx, int in_type, 
 	const hawk_ooch_t* name, hawk_ooecs_t* buf);
 
 int hawk_rtx_readiobytes (
-	hawk_rtx_t* run, int in_type, 
+	hawk_rtx_t* rtx, int in_type, 
 	const hawk_ooch_t* name, hawk_becs_t* buf);
 
 int hawk_rtx_writeioval (
-	hawk_rtx_t* run, int out_type, 
+	hawk_rtx_t* rtx, int out_type, 
 	const hawk_ooch_t* name, hawk_val_t* v);
 
 int hawk_rtx_writeiostr (
-	hawk_rtx_t* run, int out_type, 
+	hawk_rtx_t* rtx, int out_type, 
 	const hawk_ooch_t* name, hawk_ooch_t* str, hawk_oow_t len);
 
 int hawk_rtx_writeiobytes (
-	hawk_rtx_t* run, int out_type, 
+	hawk_rtx_t* rtx, int out_type, 
 	const hawk_ooch_t* name, hawk_bch_t* str, hawk_oow_t len);
 
 int hawk_rtx_flushio (
-	hawk_rtx_t* run, int out_type, const hawk_ooch_t* name);
+	hawk_rtx_t* rtx, int out_type, const hawk_ooch_t* name);
 
 int hawk_rtx_nextio_read (
-	hawk_rtx_t* run, int in_type, const hawk_ooch_t* name);
+	hawk_rtx_t* rtx, int in_type, const hawk_ooch_t* name);
 
 int hawk_rtx_nextio_write (
-	hawk_rtx_t* run, int out_type, const hawk_ooch_t* name);
+	hawk_rtx_t* rtx, int out_type, const hawk_ooch_t* name);
 
 int hawk_rtx_closeio (
-	hawk_rtx_t*    run,
+	hawk_rtx_t*        rtx,
 	const hawk_ooch_t* name,
 	const hawk_ooch_t* opt
 );
 
-void hawk_rtx_cleario (hawk_rtx_t* run);
+void hawk_rtx_flushallios (hawk_rtx_t* rtx);
+void hawk_rtx_clearallios (hawk_rtx_t* rtx);
 
 #if defined(__cplusplus)
 }
diff --git a/hawk/lib/rio.c b/hawk/lib/rio.c
index e1de7a9d..109eec8c 100644
--- a/hawk/lib/rio.c
+++ b/hawk/lib/rio.c
@@ -1039,7 +1039,7 @@ static int prepare_for_write_io_data (hawk_rtx_t* rtx, int out_type, const hawk_
 	io_mask = out_mask_map[out_type];
 
 	handler = rtx->rio.handler[io_type];
-	if (handler == HAWK_NULL)
+	if (HAWK_UNLIKELY(!handler))
 	{
 		/* no I/O handler provided */
 		hawk_rtx_seterrnum (rtx, HAWK_NULL, HAWK_EIOUSER);
@@ -1067,12 +1067,12 @@ static int prepare_for_write_io_data (hawk_rtx_t* rtx, int out_type, const hawk_
 	if (p == HAWK_NULL)
 	{
 		p = (hawk_rio_arg_t*)hawk_rtx_allocmem(rtx, HAWK_SIZEOF(hawk_rio_arg_t));
-		if (p == HAWK_NULL) return -1;
+		if (HAWK_UNLIKELY(!p)) return -1;
 
 		HAWK_MEMSET (p, 0, HAWK_SIZEOF(*p));
 
 		p->name = hawk_rtx_dupoocstr(rtx, name, HAWK_NULL);
-		if (p->name == HAWK_NULL)
+		if (HAWK_UNLIKELY(!p->name))
 		{
 			hawk_rtx_freemem (rtx, p);
 			return -1;
@@ -1422,7 +1422,7 @@ int hawk_rtx_closio_write (hawk_rtx_t* rtx, int out_type, const hawk_ooch_t* nam
 	io_mask = out_mask_map[out_type];
 
 	handler = rtx->rio.handler[io_type];
-	if (!handler)
+	if (HAWK_UNLIKELY(!handler))
 	{
 		/* no io handler provided */
 		hawk_rtx_seterrnum (rtx, HAWK_NULL, HAWK_EIOUSER);
@@ -1434,7 +1434,7 @@ int hawk_rtx_closio_write (hawk_rtx_t* rtx, int out_type, const hawk_ooch_t* nam
 		if (p->type == (io_type | io_mask) && hawk_comp_oocstr(p->name, name, 0) == 0) 
 		{
 			hawk_rio_impl_t handler;
-		       
+
 			handler = rtx->rio.handler[p->type & IO_MASK_CLEAR];
 			if (handler && handler(rtx, HAWK_RIO_CMD_CLOSE, p, HAWK_NULL, 0) <= -1) return -1;
 
@@ -1525,7 +1525,7 @@ int hawk_rtx_closeio (hawk_rtx_t* rtx, const hawk_ooch_t* name, const hawk_ooch_
 				}
 			}
 
-			if (px != HAWK_NULL) px->next = p->next;
+			if (px) px->next = p->next;
 			else rtx->rio.chain = p->next;
 
 			hawk_rtx_freemem (rtx, p->name);
@@ -1543,7 +1543,22 @@ int hawk_rtx_closeio (hawk_rtx_t* rtx, const hawk_ooch_t* name, const hawk_ooch_
 	return -1;
 }
 
-void hawk_rtx_cleario (hawk_rtx_t* rtx)
+void hawk_rtx_flushallios (hawk_rtx_t* rtx)
+{
+	hawk_rio_arg_t* rio;
+	hawk_rio_impl_t handler;
+
+	for (rio = rtx->rio.chain; rio; rio = rio->next)
+	{
+		handler = rtx->rio.handler[rio->type & IO_MASK_CLEAR];
+		if (handler)
+		{
+			handler (rtx, HAWK_RIO_CMD_FLUSH, rio, HAWK_NULL, 0);
+		}
+	}
+}
+
+void hawk_rtx_clearallios (hawk_rtx_t* rtx)
 {
 	hawk_rio_arg_t* next;
 	hawk_rio_impl_t handler;
diff --git a/hawk/lib/run.c b/hawk/lib/run.c
index 312f697c..40223c2e 100644
--- a/hawk/lib/run.c
+++ b/hawk/lib/run.c
@@ -1158,7 +1158,7 @@ static void fini_rtx (hawk_rtx_t* rtx, int fini_globals)
 
 	/* close all pending io's */
 	/* TODO: what if this operation fails? */
-	hawk_rtx_cleario (rtx);
+	hawk_rtx_clearallios (rtx);
 	HAWK_ASSERT (rtx->rio.chain == HAWK_NULL);
 
 	if (rtx->gbl.rs[0])
@@ -1672,8 +1672,8 @@ hawk_val_t* hawk_rtx_loop (hawk_rtx_t* rtx)
 	/* reset the exit level */
 	rtx->exit_level = EXIT_NONE;
 
-	/* clear any pending io's */
-	hawk_rtx_cleario (rtx);
+	/* flush all buffered io data */
+	hawk_rtx_flushallios (rtx);
 
 	return retv;
 }
@@ -1829,8 +1829,8 @@ hawk_val_t* hawk_rtx_callfun (hawk_rtx_t* rtx, hawk_fun_t* fun, hawk_val_t* args
 		hawk_rtx_refupval (rtx, v);
 	}
 
-	/* clear any pending io's */
-	hawk_rtx_cleario  (rtx);
+	/* flush all buffered io data */
+	hawk_rtx_flushallios (rtx);
 
 	/* return the return value with its reference count at least 1.
 	 * the caller of this function should count down its reference. */
diff --git a/hawk/lib/std.c b/hawk/lib/std.c
index e6b0889f..0da89358 100644
--- a/hawk/lib/std.c
+++ b/hawk/lib/std.c
@@ -2020,7 +2020,19 @@ static hawk_ooi_t awk_rio_file (hawk_rtx_t* rtx, hawk_rio_cmd_t cmd, hawk_rio_ar
 			return hawk_sio_putbchars((hawk_sio_t*)riod->handle, data, size);
 
 		case HAWK_RIO_CMD_FLUSH:
-			return hawk_sio_flush((hawk_sio_t*)riod->handle);
+		{
+			int n;
+
+			n = hawk_sio_flush((hawk_sio_t*)riod->handle);
+			if (HAWK_UNLIKELY(n <= -1))
+			{
+				/* if flushing fails, discard the buffered data
+				 * keeping the unflushed data causes causes subsequent write or close() to
+				 * flush again and again */
+				hawk_sio_drain ((hawk_sio_t*)riod->handle);
+			}
+			return n;
+		}
 
 		case HAWK_RIO_CMD_NEXT:
 			return -1;
@@ -2376,7 +2388,19 @@ static hawk_ooi_t awk_rio_console (hawk_rtx_t* rtx, hawk_rio_cmd_t cmd, hawk_rio
 			return hawk_sio_putbchars((hawk_sio_t*)riod->handle, data, size);
 
 		case HAWK_RIO_CMD_FLUSH:
-			return hawk_sio_flush((hawk_sio_t*)riod->handle);
+		{
+			int n;
+
+			n = hawk_sio_flush((hawk_sio_t*)riod->handle);
+			if (HAWK_UNLIKELY(n <= -1))
+			{
+				/* if flushing fails, discard the buffered data
+				 * keeping the unflushed data causes causes subsequent write or close() to
+				 * flush again and again */
+				hawk_sio_drain ((hawk_sio_t*)riod->handle);
+			}
+			return n;
+		}
 
 		case HAWK_RIO_CMD_NEXT:
 		{