diff --git a/test_config_syntax.sh b/test_config_syntax.sh
index a48c9c0..86a2bca 100755
--- a/test_config_syntax.sh
+++ b/test_config_syntax.sh
@@ -3,7 +3,7 @@
 set -eux
 
 docker run --rm -it \
-  --volume $(pwd)/postfix.grok:/etc/logstash/patterns.d/postfix.grok \
-  --volume $(pwd)/50-filter-postfix.conf:/usr/share/logstash/pipeline/50-filter-postfix.conf \
+  --volume "$(pwd)"/postfix.grok:/etc/logstash/patterns.d/postfix.grok \
+  --volume "$(pwd)"/50-filter-postfix.conf:/usr/share/logstash/pipeline/50-filter-postfix.conf \
   logstash:8.12.0 \
   logstash --config.test_and_exit -f /usr/share/logstash/pipeline/50-filter-postfix.conf
diff --git a/test_grok_patterns.sh b/test_grok_patterns.sh
index 08b1280..9978c83 100755
--- a/test_grok_patterns.sh
+++ b/test_grok_patterns.sh
@@ -12,4 +12,4 @@ FROM ruby:slim
 RUN gem install jls-grok minitest
 EOF
 
-docker run --volume $(pwd):"${VOLUMEPATH}" --workdir ${VOLUMEPATH} ${DOCKERIMAGE} sh -c "ruby test/test.rb"
+docker run --volume "$(pwd)":"${VOLUMEPATH}" --workdir ${VOLUMEPATH} ${DOCKERIMAGE} sh -c "ruby test/test.rb"
diff --git a/test_pipeline.sh b/test_pipeline.sh
index 338c4a6..573dde5 100755
--- a/test_pipeline.sh
+++ b/test_pipeline.sh
@@ -7,10 +7,10 @@ OUTPUT=$(mktemp tmp.logstash.out.XXXXX)
 PIPELINE=$(mktemp tmp.logstash.pipeline.XXXXX)
 
 echo Preparing input data
-echo "postfix/smtp[123]: 7EE668039: to=<admin@example.com>, relay=127.0.0.1[127.0.0.1]:2525, delay=3.6, delays=0.2/0.02/0.04/3.3, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 153053D)" > $INPUT
+echo "postfix/smtp[123]: 7EE668039: to=<admin@example.com>, relay=127.0.0.1[127.0.0.1]:2525, delay=3.6, delays=0.2/0.02/0.04/3.3, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 153053D)" > "$INPUT"
 
 echo Preparing pipeline config
-cat > $PIPELINE << EOF
+cat > "$PIPELINE" << EOF
 input {
   file {
     path => "/tmp/logstash.in"
@@ -26,9 +26,9 @@ filter {
 }
 EOF
 
-cat 50-filter-postfix.conf >> $PIPELINE
+cat 50-filter-postfix.conf >> "$PIPELINE"
 
-cat >> $PIPELINE << EOF
+cat >> "$PIPELINE" << EOF
 output {
   file {
     path => "/tmp/logstash.out"
@@ -38,32 +38,32 @@ EOF
 
 echo Starting logstash docker container
 CONTAINER_ID=$(docker run --rm --detach \
-  --volume ./${INPUT}:/tmp/logstash.in \
-  --volume ./${OUTPUT}:/tmp/logstash.out \
+  --volume ./"${INPUT}":/tmp/logstash.in \
+  --volume ./"${OUTPUT}":/tmp/logstash.out \
   --volume ./postfix.grok:/etc/logstash/patterns.d/postfix.grok \
-  --volume ./${PIPELINE}:/usr/share/logstash/pipeline/pipeline.conf \
+  --volume ./"${PIPELINE}":/usr/share/logstash/pipeline/pipeline.conf \
   logstash:8.12.0 \
   logstash -f /usr/share/logstash/pipeline/pipeline.conf)
 
-echo -n "Waiting for output from logstash "
-until test -s $OUTPUT; do
-  echo -n "."
+printf "Waiting for output from logstash "
+until test -s "$OUTPUT"; do
+  printf "."
   sleep 2
 done
 echo
 
-docker stop --time 1 $CONTAINER_ID > /dev/null
+docker stop --time 1 "$CONTAINER_ID" > /dev/null
 
-if test "$(jq .tags[0] $OUTPUT)" = '"_grok_postfix_success"'; then
+if test "$(jq .tags[0] "$OUTPUT")" = '"_grok_postfix_success"'; then
   echo Grok processing successful!
-  jq . $OUTPUT
+  jq . "$OUTPUT"
 else
   echo "Grok processing failed :<"
-  jq . $OUTPUT
+  jq . "$OUTPUT"
   exit 1
 fi
 
 echo Cleaning up
-rm -f $INPUT $OUTPUT $PIPELINE
+rm -f "$INPUT" "$OUTPUT" "$PIPELINE"
 
-echo Done
\ No newline at end of file
+echo Done