diff --git a/haproxy.sh b/haproxy.sh
index 4ebb9eb..2bd74e8 100644
--- a/haproxy.sh
+++ b/haproxy.sh
@@ -22,19 +22,19 @@ echo
 
 checkos(){
     if [[ -f /etc/redhat-release ]]; then
-        OS=CentOS
-    elif cat /etc/issue | grep -q -E -i "debian"; then
-        OS=Debian
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
-        OS=Ubuntu
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
-        OS=CentOS
-    elif cat /proc/version | grep -q -E -i "debian"; then
-        OS=Debian
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
-        OS=Ubuntu
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
-        OS=CentOS
+        OS="centos"
+    elif cat /etc/issue | grep -Eqi "debian"; then
+        OS="debian"
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
+        OS="ubuntu"
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
+        OS="centos"
+    elif cat /proc/version | grep -Eqi "debian"; then
+        OS="debian"
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
+        OS="ubuntu"
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
+        OS="centos"
     else
         echo "Not supported OS, Please reinstall OS and try again."
         exit 1
@@ -169,7 +169,7 @@ EOF
 
 install(){
     # Install haproxy
-    if [ "${OS}" == 'CentOS' ]; then
+    if [ "${OS}" == "centos" ]; then
         yum install -y haproxy
     else
         apt-get -y update
@@ -183,7 +183,7 @@ install(){
         config_haproxy
         echo "Config haproxy completed..."
 
-        if [ "${OS}" == 'CentOS' ]; then
+        if [ "${OS}" == "centos" ]; then
             chkconfig --add haproxy
             chkconfig haproxy on
         else
diff --git a/shadowsocks-all.sh b/shadowsocks-all.sh
index 70eb543..e12e33e 100644
--- a/shadowsocks-all.sh
+++ b/shadowsocks-all.sh
@@ -71,22 +71,22 @@ check_sys() {
     if [ -f /etc/redhat-release ]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi
diff --git a/shadowsocks-go.sh b/shadowsocks-go.sh
index 1c50d56..5ae3d58 100644
--- a/shadowsocks-go.sh
+++ b/shadowsocks-go.sh
@@ -41,22 +41,22 @@ check_sys(){
     if [[ -f /etc/redhat-release ]]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi
diff --git a/shadowsocks-libev-debian.sh b/shadowsocks-libev-debian.sh
index e7e24cd..9de13fb 100644
--- a/shadowsocks-libev-debian.sh
+++ b/shadowsocks-libev-debian.sh
@@ -98,22 +98,22 @@ check_sys(){
     if [[ -f /etc/redhat-release ]]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi
diff --git a/shadowsocks-libev.sh b/shadowsocks-libev.sh
index d75c01a..952b0df 100644
--- a/shadowsocks-libev.sh
+++ b/shadowsocks-libev.sh
@@ -98,22 +98,22 @@ check_sys(){
     if [[ -f /etc/redhat-release ]]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi
diff --git a/shadowsocks.sh b/shadowsocks.sh
index f832322..1581c3f 100644
--- a/shadowsocks.sh
+++ b/shadowsocks.sh
@@ -49,22 +49,22 @@ check_sys(){
     if [[ -f /etc/redhat-release ]]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi
diff --git a/shadowsocksR.sh b/shadowsocksR.sh
index a707fd4..d89066d 100644
--- a/shadowsocksR.sh
+++ b/shadowsocksR.sh
@@ -49,22 +49,22 @@ check_sys(){
     if [[ -f /etc/redhat-release ]]; then
         release="centos"
         systemPackage="yum"
-    elif cat /etc/issue | grep -q -E -i "debian"; then
+    elif cat /etc/issue | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "ubuntu"; then
+    elif cat /etc/issue | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /etc/issue | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /etc/issue | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
-    elif cat /proc/version | grep -q -E -i "debian"; then
+    elif cat /proc/version | grep -Eqi "debian"; then
         release="debian"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "ubuntu"; then
+    elif cat /proc/version | grep -Eqi "ubuntu"; then
         release="ubuntu"
         systemPackage="apt"
-    elif cat /proc/version | grep -q -E -i "centos|red hat|redhat"; then
+    elif cat /proc/version | grep -Eqi "centos|red hat|redhat"; then
         release="centos"
         systemPackage="yum"
     fi