Shellcheck fixes

context/s3-purge.sh

 #!/bin/bash
 
-export BUCKET_NAME=$(cat /s3_bucket)
-export EXPIRE_AGE_DAYS=$(cat /s3_expire_days)
+BUCKET_NAME=$(cat /s3_bucket)
+export BUCKET_NAME
 
-s4cmd --config=/s3_config ls s3://$BUCKET_NAME | while read -r line;
+EXPIRE_AGE_DAYS=$(cat /s3_expire_days)
+export EXPIRE_AGE_DAYS
+
+s4cmd --config=/s3_config ls s3://"${BUCKET_NAME}" | while read -r line;
   do
-    createDate=`echo $line|awk {'print $1" "$2'}`
-    createDate=`date -d"$createDate" +%s`
-    olderThan=`date -d"-$EXPIRE_AGE_DAYS" +%s`
+    createDate=$(echo "$line"|awk '{print $1" "$2}')
+    createDate=$(date -d"$createDate" +%s)
+    olderThan=$(date -d"-$EXPIRE_AGE_DAYS" +%s)
     if [[ $createDate -lt $olderThan ]]
       then
-        fileName=`echo $line|awk {'print $4'}`
-        echo $fileName
+        fileName=$(echo "$line"|awk '{print $4}')
+        echo "$fileName"
         if [[ $fileName != "" ]]
           then
             s4cmd --config=/s3_config del "$fileName"