diff --git a/.drone.yml b/.drone.yml
new file mode 100644
index 0000000..d95d49d
--- /dev/null
+++ b/.drone.yml
@@ -0,0 +1,11 @@
+---
+kind: pipeline
+type: docker
+name: lint
+
+steps:
+  - name: ShellCheck
+    image: koalaman/shellcheck-alpine:v0.7.1
+    commands:
+      - shellcheck -e SC2181 pdf-optimize
+...
diff --git a/README.md b/README.md
index 97e72f5..8f7754a 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,5 @@
 # pdf-optimize
+[![Build Status](https://drone.auro.re/api/badges/otthorn/pdf-optimize/status.svg)](https://drone.auro.re/otthorn/pdf-optimize)
 
 pdf-optimize is a simple script to optimize pdf using ghostscript.
 You need to have ghoscript installed on your machine.
diff --git a/pdf-optimize b/pdf-optimize
index d2bd9b5..ee94899 100755
--- a/pdf-optimize
+++ b/pdf-optimize
@@ -78,7 +78,7 @@ function arg_parse
 
 function yes_or_no
 {
-	read -p "$* [y/N]: " ans
+	read -pr "$* [y/N]: " ans
 	case "$ans" in
 		[yY] | [yY]es )     return 0;;
 		* )                 echo "Aborting"; return 1;;
@@ -103,8 +103,8 @@ ${bold}$output_path${normal}."
 		   -dNOPAUSE \
 		   -dQUIET \
 		   -dBATCH \
-		   -sOutputFile=$output_path \
-		   $input_path
+		   -sOutputFile="$output_path" \
+		   "$input_path"
 	else
 		echo "input_path=$input_path";
 		echo "output_path=$output_path";
@@ -117,8 +117,8 @@ ${bold}$output_path${normal}."
 		   -dPDFSETTINGS=/prepress \
 		   -dNOPAUSE \
 		   -dBATCH \
-		   -sOutputFile=$output_path \
-		   $input_path 
+		   -sOutputFile="$output_path" \
+		   "$input_path" 
 	fi
 	
 	# catching errors
@@ -136,11 +136,11 @@ ${bold}$output_path${normal}."
 
 function compute_compression
 {
-	input_size=`du "$input_path" | cut -f1`
-	output_size=`du "$output_path" | cut -f1`
-	percentage=`echo "scale=1;$output_size / $input_size * 100" | bc -l`
-	input_size_h=`du -h "$input_path" | cut -f1`
-	output_size_h=`du -h "$output_path" | cut -f1`
+	input_size=$(du "$input_path" | cut -f1)
+	output_size=$(du "$output_path" | cut -f1)
+	percentage=$(echo "scale=1;$output_size / $input_size * 100" | bc -l)
+	input_size_h=$(du -h "$input_path" | cut -f1)
+	output_size_h=$(du -h "$output_path" | cut -f1)
 
 	echo "Size reduced from ${bold}$input_size_h${normal} to \
 ${bold}$output_size_h${normal} [$percentage %]"