diff --git a/.travis.yml b/.travis.yml
index 7cc5202..f004410 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ addons:
     - shellcheck
 
 script:
-    - shellcheck -e SC2034 -e SC2166 duplicity-backup.sh duplicity-backup.conf.example
+    - shellcheck -e SC2034 duplicity-backup.sh duplicity-backup.conf.example
 
 matrix:
   fast_finish: true
diff --git a/duplicity-backup.sh b/duplicity-backup.sh
index fc771a3..0dba351 100755
--- a/duplicity-backup.sh
+++ b/duplicity-backup.sh
@@ -97,7 +97,7 @@ while getopts ":c:t:bfvelsnd-:" opt; do
         restore)
           COMMAND=${OPTARG}
           # We try to find the optional value [restore dest]
-          if [ ! -z "${!OPTIND:0:1}" -a ! "${!OPTIND:0:1}" = "-" ]; then
+          if [ ! -z "${!OPTIND:0:1}" ] && [ ! "${!OPTIND:0:1}" = "-" ]; then
             RESTORE_DEST=${!OPTIND}
             OPTIND=$(( OPTIND + 1 )) # we found it, move forward in arg parsing
           fi
@@ -107,28 +107,28 @@ while getopts ":c:t:bfvelsnd-:" opt; do
         restore-file|restore-dir)
           COMMAND=${OPTARG}
           # We try to find the first optional value [file to restore]
-          if [ ! -z "${!OPTIND:0:1}" -a ! "${!OPTIND:0:1}" = "-" ]; then
+          if [ ! -z "${!OPTIND:0:1}" ] && [ ! "${!OPTIND:0:1}" = "-" ]; then
             FILE_TO_RESTORE=${!OPTIND}
             OPTIND=$(( OPTIND + 1 )) # we found it, move forward in arg parsing
           else
             continue # no value for the restore-file option, skip the rest
           fi
           # We try to find the second optional value [restore dest]
-          if [ ! -z "${!OPTIND:0:1}" -a ! "${!OPTIND:0:1}" = "-" ]; then
+          if [ ! -z "${!OPTIND:0:1}" ] && [ ! "${!OPTIND:0:1}" = "-" ]; then
             RESTORE_DEST=${!OPTIND}
             OPTIND=$(( OPTIND + 1 )) # we found it, move forward in arg parsing
           fi
         ;;
         config) # set the config file from the command line
           # We try to find the config file
-          if [ ! -z "${!OPTIND:0:1}" -a ! "${!OPTIND:0:1}" = "-" ]; then
+          if [ ! -z "${!OPTIND:0:1}" ] && [ ! "${!OPTIND:0:1}" = "-" ]; then
             CONFIG=${!OPTIND}
             OPTIND=$(( OPTIND + 1 )) # we found it, move forward in arg parsing
           fi
         ;;
         time) # set the restore time from the command line
           # We try to find the restore time
-          if [ ! -z "${!OPTIND:0:1}" -a ! "${!OPTIND:0:1}" = "-" ]; then
+          if [ ! -z "${!OPTIND:0:1}" ] && [ ! "${!OPTIND:0:1}" = "-" ]; then
             TIME=${!OPTIND}
             OPTIND=$(( OPTIND + 1 )) # we found it, move forward in arg parsing
           fi
@@ -167,7 +167,7 @@ while getopts ":c:t:bfvelsnd-:" opt; do
 done
 
 # Read config file if specified
-if [ ! -z "${CONFIG}" -a -f "${CONFIG}" ];
+if [ ! -z "${CONFIG}" ] && [ -f "${CONFIG}" ];
 then
   # shellcheck source=duplicity-backup.conf.example
   . "${CONFIG}"
@@ -214,7 +214,7 @@ if [ "${ENCRYPTION}" = "yes" ]; then
   if [ ! -z "${GPG_ENC_KEY}" ] && [ ! -z "${GPG_SIGN_KEY}" ]; then
     if [ "${HIDE_KEY_ID}" = "yes" ]; then
       ENCRYPT="--hidden-encrypt-key=${GPG_ENC_KEY}"
-      if [ "${COMMAND}" != "restore" -a "${COMMAND}" != "restore-file" -a "${COMMAND}" != "restore-dir" ]; then
+      if [ "${COMMAND}" != "restore" ] && [ "${COMMAND}" != "restore-file" ] && [ "${COMMAND}" != "restore-dir" ]; then
         ENCRYPT="${ENCRYPT} --sign-key=${GPG_SIGN_KEY}"
       fi
     else
@@ -270,10 +270,10 @@ if  [ "$(echo "${DEST}" | cut -c 1,2)" = "s3" ]; then
   S3CMD="$(which s3cmd)"
   if [ ! -x "${S3CMD}" ]; then
     echo "${NO_S3CMD}"; S3CMD_AVAIL=false
-  elif [ -z "${S3CMD_CONF_FILE}" -a ! -f "${HOME}/.s3cfg" ]; then
+  elif [ -z "${S3CMD_CONF_FILE}" ] && [ ! -f "${HOME}/.s3cfg" ]; then
     S3CMD_CONF_FOUND=false
     echo "${NO_S3CMD_CFG}"; S3CMD_AVAIL=false
-  elif [ ! -z "${S3CMD_CONF_FILE}" -a ! -f "${S3CMD_CONF_FILE}" ]; then
+  elif [ ! -z "${S3CMD_CONF_FILE}" ] && [ ! -f "${S3CMD_CONF_FILE}" ]; then
     S3CMD_CONF_FOUND=false
     echo "${S3CMD_CONF_FILE} not found, check S3CMD_CONF_FILE variable in duplicity-backup's configuration!";
     echo "${NO_S3CMD_CFG}";
@@ -281,7 +281,7 @@ if  [ "$(echo "${DEST}" | cut -c 1,2)" = "s3" ]; then
   else
     S3CMD_AVAIL=true
     S3CMD_CONF_FOUND=true
-    if [ ! -z "${S3CMD_CONF_FILE}" -a -f "${S3CMD_CONF_FILE}" ]; then
+    if [ ! -z "${S3CMD_CONF_FILE}" ] && [ -f "${S3CMD_CONF_FILE}" ]; then
       # if conf file specified and it exists then add it to the command line for s3cmd
       S3CMD="${S3CMD} -c ${S3CMD_CONF_FILE}"
     fi
@@ -654,7 +654,7 @@ duplicity_cleanup_failed()
 
 setup_passphrase()
 {
-  if [ ! -z "${GPG_ENC_KEY}" -a ! -z "${GPG_SIGN_KEY}" -a "${GPG_ENC_KEY}" != "${GPG_SIGN_KEY}" ]; then
+  if [ ! -z "${GPG_ENC_KEY}" ] && [ ! -z "${GPG_SIGN_KEY}" ] && [ "${GPG_ENC_KEY}" != "${GPG_SIGN_KEY}" ]; then
     echo -n "Please provide the passphrase for decryption (GPG key 0x${GPG_ENC_KEY}): "
     builtin read -s -r ENCPASSPHRASE
     echo -ne "\n"
@@ -702,7 +702,7 @@ backup_this_script()
   echo "You are backing up: "
   echo "      1. ${SCRIPTPATH}"
 
-  if [ ! -z "${GPG_ENC_KEY}" -a ! -z "${GPG_SIGN_KEY}" ]; then
+  if [ ! -z "${GPG_ENC_KEY}" ] && [ ! -z "${GPG_SIGN_KEY}" ]; then
     if [ "${GPG_ENC_KEY}" = "${GPG_SIGN_KEY}" ]; then
       echo "      2. GPG Secret encryption and sign key: ${GPG_ENC_KEY}"
     else
@@ -712,12 +712,12 @@ backup_this_script()
     echo "      2. GPG Secret encryption and sign key: none (symmetric encryption)"
   fi
 
-  if [ ! -z "${CONFIG}" -a -f "${CONFIG}" ];
+  if [ ! -z "${CONFIG}" ] && [ -f "${CONFIG}" ];
   then
     echo "      3. Config file: ${CONFIG}"
   fi
 
-  if [ ! -z "${INCEXCFILE}" -a -f "${INCEXCFILE}" ];
+  if [ ! -z "${INCEXCFILE}" ] && [ -f "${INCEXCFILE}" ];
   then
     echo "      4. Include/Exclude globbing file: ${INCEXCFILE}"
   fi
@@ -734,17 +734,17 @@ backup_this_script()
   mkdir -p "${TMPDIR}"
   cp "${SCRIPTPATH}" "${TMPDIR}"/
 
-  if [ ! -z "${CONFIG}" -a -f "${CONFIG}" ];
+  if [ ! -z "${CONFIG}" ] && [ -f "${CONFIG}" ];
   then
     cp "${CONFIG}" "${TMPDIR}"/
   fi
 
-  if [ ! -z "${INCEXCFILE}" -a -f "${INCEXCFILE}" ];
+  if [ ! -z "${INCEXCFILE}" ] && [ -f "${INCEXCFILE}" ];
   then
     cp "${INCEXCFILE}" "${TMPDIR}"/
   fi
 
-  if [ ! -z "${GPG_ENC_KEY}" -a ! -z "${GPG_SIGN_KEY}" ]; then
+  if [ ! -z "${GPG_ENC_KEY}" ] && [ ! -z "${GPG_SIGN_KEY}" ]; then
     GPG_TTY=$(tty)
     export GPG_TTY
     if [ "${GPG_ENC_KEY}" = "${GPG_SIGN_KEY}" ]; then