use $USER instead of whoami

bin/psu

diff --git a/bin/psu b/bin/psu
index da6d8d4..b337a8c 100755
--- a/bin/psu
+++ b/bin/psu
@@ -7,10 +7,9 @@
 	shift
 fi
 
-user=`whoami`
 case $# in
 0)
-	user=`whoami`
+	user=$USER
 	;;
 1)
 	user=$1