diff --git a/automount.sh b/automount.sh
index 7ee555c..41b11e4 100755
--- a/automount.sh
+++ b/automount.sh
@@ -15,29 +15,29 @@ while true; do
 	dev_plug_state="$(lsblk | grep $device)"
 	dev_mount_state="$(mount | grep $device)"
 
-	if [ ! -z "$dev_plug_state" ] && [ -z "$dev_mount_state" ]; then
+	if [ -n "$dev_plug_state" ] && [ -z "$dev_mount_state" ]; then
 		echo "Mount /dev/$device on $mountpoint with options $mountoptions"
 		sudo mount /dev/$device $mountpoint -o $mountoptions
 		echo "Done!"
 
-	elif [ ! -z "$dev_plug_state" ] && [ ! -z "$dev_mount_state" ]; then
+	elif [ -n "$dev_plug_state" ] && [ -n "$dev_mount_state" ]; then
 		echo "/dev/$device is already mounted on $mountpoint"
 
 	elif [ -z "$dev_plug_state" ] && [ -z "$dev_mount_state" ]; then
 		echo "/dev/$device not plugged in and is not mounted!"
 
-	elif [ -z "$dev_plug_state" ] && [ ! -z "$dev_mount_state" ]; then
+	elif [ -z "$dev_plug_state" ] && [ -n "$dev_mount_state" ]; then
 		echo "/dev/$device is not plugged in and is mounted on $mountpoint"
 		
 		playershstat="$(pgrep $playersh)"
-		if [ ! -z "$playershstat" ]; then
+		if [ -n "$playershstat" ]; then
 			echo "Terminating $playersh"
 			pkill $playersh
 			echo "Done!"
 		fi
 
 		playerstat="$(pgrep $player)"
-		if [ ! -z "$playerstat" ]; then
+		if [ -n "$playerstat" ]; then
 			echo "Terminating $player"
 			pkill $player
 			echo "Done!"
diff --git a/check_playerproc.sh b/check_playerproc.sh
index 7d8b29c..851c4e1 100755
--- a/check_playerproc.sh
+++ b/check_playerproc.sh
@@ -33,7 +33,7 @@ $gpiocmd write $gpiopin_led_b 0
 
 while true; do
 
-	if [ ! -z "$(pgrep $player)" ]; then
+	if [ -n "$(pgrep $player)" ]; then
 		$gpiocmd write $gpiopin_led_b 1
 		sleep 0.1
 		$gpiocmd write $gpiopin_led_b 0
diff --git a/poll_button.sh b/poll_button.sh
index 768fb37..1775236 100755
--- a/poll_button.sh
+++ b/poll_button.sh
@@ -45,7 +45,7 @@ while true; do
 	$gpiocmd mode $gpiopin_led_r out
 	$gpiocmd write $gpiopin_led_g 1
 	while [ "$($gpiocmd read $gpiopin_sw)" -eq "1" ] && [ "$counter" -lt "$countermax" ]; do
-		counter="$(($counter + 1))"
+		counter="$((counter + 1))"
 		#echo "$counter"
 		sleep $buttonpolling
 	done
@@ -61,7 +61,7 @@ while true; do
 	$gpiocmd mode $gpiopin_led_r out
 	$gpiocmd write $gpiopin_led_g 1
 	while [ "$($gpiocmd read $gpiopin_sw)" -eq "1" ] && [ "$counter" -lt "$countermax" ]; do
-		counter="$(($counter + 1))"
+		counter="$((counter + 1))"
 		#echo "$counter"
 		sleep $buttonpolling
 	done
@@ -77,7 +77,7 @@ while true; do
 	$gpiocmd mode $gpiopin_led_r out
 	$gpiocmd write $gpiopin_led_g 1
 	while [ "$($gpiocmd read $gpiopin_sw)" -eq "1" ] && [ "$counter" -lt "$countermax" ]; do
-		counter="$(($counter + 1))"
+		counter="$((counter + 1))"
 		#echo "$counter"
 		sleep $buttonpolling
 	done
diff --git a/randomvideo.sh b/randomvideo.sh
index 50f8425..507d0fc 100755
--- a/randomvideo.sh
+++ b/randomvideo.sh
@@ -37,7 +37,7 @@ while true; do
 	if [ -z "$mountstat" ]; then
 		folder="$folderint"
 
-	elif [ ! -z "$mountstat" ]; then
+	elif [ -n "$mountstat" ]; then
 		folder="$folderext"
 	
 	fi
diff --git a/view_birdcam.sh b/view_birdcam.sh
index 30b0b44..292fcfe 100755
--- a/view_birdcam.sh
+++ b/view_birdcam.sh
@@ -37,11 +37,11 @@ streamurl="rtsp://$1:554/user=admin&password=&channel=1&stream=0.sdp?real_stream
 randomvideosh="/home/pi/birdcam/randomvideo.sh"						### var: path to random video script
 randomvideoproc="randomvideo.sh"							### var: name of process for random video script
 
-if [ ! -z "$(pgrep $playerproc)" ]; then
+if [ -n "$(pgrep $playerproc)" ]; then
 	pkill $playerproc
 fi
 
-if [ ! -z "$(pgrep $randomvideoproc)" ]; then
+if [ -n "$(pgrep $randomvideoproc)" ]; then
 	pkill $randomvideoproc
 fi