diff --git a/agent/netflow/netflow_handler.sh b/agent/netflow/netflow_handler.sh
index 901eb5f..a3f13aa 100755
--- a/agent/netflow/netflow_handler.sh
+++ b/agent/netflow/netflow_handler.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-if [ -z "$1" ]; then
+if [[ -z "$1" ]]; then
     echo "missing filename"
     exit
 fi
@@ -8,7 +8,7 @@ fi
 PATH=/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin
 tmpdir='/tmp/djing_flow'
 
-if [ ! -d "$tmpdir" ]; then
+if [[ ! -d "$tmpdir" ]]; then
     mkdir -p "$tmpdir"
 fi
 
diff --git a/agent/netflow/start_netflow.sh b/agent/netflow/start_netflow.sh
index 5d42449..b803907 100755
--- a/agent/netflow/start_netflow.sh
+++ b/agent/netflow/start_netflow.sh
@@ -2,7 +2,7 @@
 
 PATH=/bin:/usr/local/sbin:/usr/local/bin:/usr/bin
 
-if ! [ -n "$1" ]; then
+if ! [[ -n "$1" ]]; then
     echo 'Missing port parameter'
     exit
 fi
@@ -11,7 +11,7 @@ port=$1
 DIRECTORY=`dirname $(readlink -e "$0")`
 
 tdir="/tmp/djing_flow/${port}"
-if [ -d "${tdir}" ]; then
+if [[ -d "${tdir}" ]]; then
     echo "Warning: directory '${tdir}' exists, clean all"
     rm -f ${tdir}/ft*
 else