Index: tkdiff
===================================================================
diff --git a/tkdiff b/tkdiff
--- a/tkdiff	(revision 188)
+++ b/tkdiff	(revision 189)
@@ -111,7 +111,7 @@
 }
 
 # Determine the name of the temporary directory, the rc file name,
-# and possible VPATH EnvVar, all of which are platform dependent.
+# NULLdev, and possible VPATH EnvVar, all of which are platform dependent.
 #
 # Much MAY likely be overridden by a preference in .tkdiffrc,
 # EXCEPT (obviously) when no such file actually exists yet
@@ -126,6 +126,9 @@
             set opts(tmpdir) C:/temp
         }
 
+        # Reserved filename which is actually a NULL device
+        set opts(NULLdev) "nul"
+
         # Split up and store a VPATH if it exists
         if {[info exists ::env(VPATH)]} {
             set finfo(Vpath) [split $::env(VPATH) ";"]
@@ -145,6 +148,9 @@
             set opts(tmpdir) $::env(TMPDIR)
         }  {set opts(tmpdir) /tmp }
 
+        # Reserved filename which is actually a NULL device (Unix-like platforms)
+        set opts(NULLdev) "/dev/null"
+
         # Split up and store a VPATH if it exists
         if {[info exists ::env(VPATH)]} {
             set finfo(Vpath) [split $::env(VPATH) ":"]
@@ -2106,7 +2112,7 @@
 #           1  Failed   (PLUS a 'pushed' HARD-error message to the caller)
 ###############################################################################
 proc get-file {fn ndx {probe 0}} {
-    global g finfo
+    global g opts finfo
 
     # Ancestor files are stored into a slightly adjusted array element name 
     #   N.B> 'ndx' AS PASSED *can* be an EXPRESSION (not just a number): resolve!
@@ -2121,7 +2127,7 @@
     } elseif {!$tildechk} {
         # DO NOT REPORT non-existence if this attempt was ONLY a probe
         if {$probe} { return 1 } { set MSG "File '$fn' does not exist" }
-    } elseif {[file isfile $fn]} {
+    } elseif {[file isfile $fn] || $fn == $opts(NULLdev)} {
         set finfo(${A}lbl,$ndx) [shortNm [set finfo(${A}pth,$ndx) "$fn"]]
     } else { set MSG "'$fn' exists, but is not a file" }
 
@@ -2857,7 +2863,7 @@
 # Align various label decorations to the CURRENT input file pairing
 ###############################################################################
 proc alignDecor {pairnum} {
-    global g w finfo
+    global g w opts finfo
 
     # Establish if 3way mode is NOW active and what file indices are in use
     set g(is3way) [info exists finfo(albl,$pairnum)]
@@ -2874,7 +2880,8 @@
             set finfo(lbl,$LR) $finfo(ulbl,$ndx($n))    ;# Override lbl display
         } else {set finfo(lbl,$LR) $finfo(lbl,$ndx($n))}
 
-        if {![info exists finfo(tmp,$ndx($n))]} {
+        if {![info exists finfo(tmp,$ndx($n))] \
+            && $finfo(pth,$ndx($n)) != $opts(NULLdev)} {
             #   (N.B> Tip data will ALSO be used by report generation heading)
             set    g(tooltip,${LR}Label) "{$finfo(pth,$ndx($n))\n"
             append g(tooltip,${LR}Label) \