Admin/PLATFORMS

--- a/Admin/PLATFORMS	Wed Feb 12 13:33:05 2014 +0100
+++ b/Admin/PLATFORMS	Wed Feb 12 13:53:11 2014 +0100
@@ -122,3 +122,6 @@
   identifies the JVM platform.  Since a particular Java version is
   always bundled with Isabelle, the resulting settings also provide
   some clues about its platform, without running it.
+
+* Common Unix tools like /bin/sh, /bin/kill, sed, ulimit are
+  notoriously non-portable an should be avoided.
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