auto detect the sed command for osx.

@@ -504,11 +504,7 @@ 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
-    if [ $OS_IS_OSX = YES ]; then
-        sed -i '' "s/^.user  nobody;/user `whoami`;/g" ${SRS_OBJS}/nginx/conf/nginx.conf
-    else
-        sed -i "s/^.user  nobody;/user `whoami`;/g" ${SRS_OBJS}/nginx/conf/nginx.conf
-    fi
+    $SED '' "s/^.user  nobody;/user `whoami`;/g" ${SRS_OBJS}/nginx/conf/nginx.conf
 fi
 
 # the demo dir.

 #!/bin/bash
 
+OS_IS_OSX=NO
+uname -s|grep Darwin >/dev/null 2>&1
+ret=$?; if [[ 0 -eq $ret ]]; then
+    OS_IS_OSX=YES
+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
 #
@@ -59,7 +70,7 @@ function build_module_hpp()
     for item in ${SRS_LIBRTMP_OBJS[*]}; do
         FILE_NAME="${item%.*}"
         echo "// following is generated by ${FILE_NAME}.hpp" >> $FILE &&
-        sed -i "s|#include <srs_|//#include <srs_|g" $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.hpp &&
+        $SED "s|#include <srs_|//#include <srs_|g" $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.hpp &&
         cat $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.hpp >>$FILE
         ret=$?; if [[ $ret -ne 0 ]]; then 
             echo -e "${RED}failed to generate the srs_librtmp.cpp by ${FILE_NAME}.hpp. {${BLACK}"
@@ -78,7 +89,7 @@ function build_module_cpp()
     for item in ${SRS_LIBRTMP_OBJS[*]}; do
         FILE_NAME="${item%.*}"
         echo "// following is generated by ${FILE_NAME}.cpp" >> $FILE &&
-        sed -i "s|#include <srs_|//#include <srs_|g" $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.cpp &&
+        $SED "s|#include <srs_|//#include <srs_|g" $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.cpp &&
         cat $SRS_EXPORT_LIBRTMP_SINGLE/${FILE_NAME}.cpp >>$FILE
         ret=$?; if [[ $ret -ne 0 ]]; then 
             echo -e "${RED}failed to generate the srs_librtmp.cpp by ${FILE_NAME}.cpp. {${BLACK}"