2 files changed, 10 insertions, 3 deletions
diff --git a/bin/9 b/bin/9
index ff1a928d..33b0d89c 100755
--- a/bin/9
+++ b/bin/9
@@ -1,7 +1,13 @@
 #!/bin/sh
 
-export PLAN9=/usr/local/plan9
-export PATH=$PLAN9/bin:$PATH
+export PLAN9=${PLAN9:-/usr/local/plan9}
+case "$PATH" in
+$PLAN9/bin:*)
+	;;
+*)
+	export PATH=$PLAN9/bin:$PATH
+	;;
+esac
 
 case $# in
 [1-9]*)
diff --git a/bin/9.rc b/bin/9.rc
index 1fb75d23..354976d3 100755
--- a/bin/9.rc
+++ b/bin/9.rc
@@ -1,6 +1,7 @@
 #!/usr/local/plan9/bin/rc
 
-PLAN9=/usr/local/plan9
+if(~ $#PLAN9 0)
+	PLAN9=/usr/local/plan9
 if(! ~ $path(1) $PLAN9/bin)
 	path=($PLAN9/bin $path)