diff --git a/trunk/auto/depends.sh b/trunk/auto/depends.sh
index 8974c3d33..3b5c74c50 100644
--- a/trunk/auto/depends.sh
+++ b/trunk/auto/depends.sh
@@ -513,7 +513,7 @@ if [ $__SRS_BUILD_NGINX = YES ]; then
     # srs will write ts/m3u8 file use current user,
     # nginx default use nobody, so cannot read the ts/m3u8 created by srs.
     cp ${SRS_OBJS}/nginx/conf/nginx.conf ${SRS_OBJS}/nginx/conf/nginx.conf.bk
-    $SED '' "s/^.user  nobody;/user `whoami`;/g" ${SRS_OBJS}/nginx/conf/nginx.conf
+    $SED "s/^.user  nobody;/user `whoami`;/g" ${SRS_OBJS}/nginx/conf/nginx.conf
 fi
 
 # the demo dir.
diff --git a/trunk/auto/generate-srs-librtmp-single.sh b/trunk/auto/generate-srs-librtmp-single.sh
index 390e438ca..191d33d0f 100755
--- a/trunk/auto/generate-srs-librtmp-single.sh
+++ b/trunk/auto/generate-srs-librtmp-single.sh
@@ -7,10 +7,6 @@ ret=$?; if [[ 0 -eq $ret ]]; then
 fi
 echo "Is OSX: ${OS_IS_OSX}"
 
-# the sed command
-SED="sed -i"
-if [ $OS_IS_OSX = YES ]; then SED="sed -i ''"; fi
-
 # when export srs-librtmp single files
 # package the whole project to srs_librtmp.h and srs_librtmp.cpp
 #
diff --git a/trunk/auto/setup_variables.sh b/trunk/auto/setup_variables.sh
index d1d643b4f..bb517aef1 100644
--- a/trunk/auto/setup_variables.sh
+++ b/trunk/auto/setup_variables.sh
@@ -28,3 +28,7 @@ if [[ -z $SrsArmCXX ]]; then SrsArmCXX=$__SrsArmCXX; fi
 if [[ -z $SrsArmAR ]]; then SrsArmAR=$__SrsArmAR; fi
 if [[ -z $SrsArmLD ]]; then SrsArmLD=$__SrsArmLD; fi
 if [[ -z $SrsArmRANDLIB ]]; then SrsArmRANDLIB=$__SrsArmRANDLIB; fi
+
+# the sed command
+SED="sed -i"
+if [ $OS_IS_OSX = YES ]; then SED="sed -i ''"; fi