diff -r 1cfa0ddc8c2c -r 527b5f1b7520 src/Pure/mk
--- a/src/Pure/mk	Wed Dec 18 12:41:48 1996 +0100
+++ b/src/Pure/mk	Wed Dec 18 12:42:20 1996 +0100
@@ -4,10 +4,7 @@
 #
 # mk - build Pure Isabelle.
 #
-# Notes:
-#   (1) make sure the Isabelle bin dir is in PATH (try 'which isabelle')
-#   (2) make sure etc/settings are appropriate
-#   (3) then cd here and run ./mk
+# Assumes to be called via Isabelle make utility (cf. IsaMakefile).
 
 
 ## diagnostics
@@ -21,16 +18,17 @@
 
 ## main
 
-ML_SYSTEM=$(isatool getenv ML_SYSTEM)
 ML_SYSTEM_BASE=$(echo $ML_SYSTEM | cut -f1 -d-)
-[ -z "$ML_SYSTEM" ] && fail "Missing ML system settings! Unable to build Isabelle."
+[ -z "$ML_SYSTEM" ] && fail "Missing ML system settings! Probably not run via 'isatool make'?."
 
 COMPAT=""
 [ -f "ML-Systems/$ML_SYSTEM_BASE.ML" ] && COMPAT="ML-Systems/$ML_SYSTEM_BASE.ML"
 [ -f "ML-Systems/$ML_SYSTEM.ML" ] && COMPAT="ML-Systems/$ML_SYSTEM.ML"
 [ -z "$COMPAT" ] && fail "Missing compatibility file for ML system \"$ML_SYSTEM\"!"
 
-exec isabelle \
+$ISABELLE_HOME/bin/isabelle \
   -e "val ml_system = \"$ML_SYSTEM\";" \
   -e "use\"$COMPAT\"; use\"ROOT.ML\" handle _ => exit 1;" \
   -cq SYSTEM Pure
+
+chmod -w $ISABELLE_OUTPUT_DIR/Pure