diff --git a/helper/build_config b/helper/build_config
index 6cf79e58..7d6a1bb6 100755
--- a/helper/build_config
+++ b/helper/build_config
@@ -17,7 +17,7 @@ CONFIG_POOL="${CONFIG_POOL:-/etc}"
 FUNCTIONS="${FUNCTIONS:-/usr/share/ngcp-ngcpcfg/functions/}"
 HELPER="${HELPER:-/usr/share/ngcp-ngcpcfg/helper/}"
 
-. ${FUNCTIONS}/main
+. "${FUNCTIONS}"/main
 
 # main script
 
@@ -37,15 +37,15 @@ export output_file="${y}" # like /etc/mysql/my.cnf, export variable
 if [ -r "${NGCPCTL_MAIN}/templates/${output_file}.prebuild" ] ; then
   log_info "Executing prebuild for ${output_file}"
   bash "${NGCPCTL_MAIN}/templates/${output_file}.prebuild"
-elif [ -r "${NGCPCTL_MAIN}/templates/$(dirname ${output_file})/ngcpcfg.prebuild" ] ; then
+elif [ -r "${NGCPCTL_MAIN}/templates/$(dirname "${output_file}")/ngcpcfg.prebuild" ] ; then
   log_info "Executing prebuild for ${output_file}"
-  bash "${NGCPCTL_MAIN}/templates/$(dirname ${output_file})/ngcpcfg.prebuild"
+  bash "${NGCPCTL_MAIN}/templates/$(dirname "${output_file}")/ngcpcfg.prebuild"
 fi
 
 # if output directory does not exist yet, create it
-if ! [ -d "$(dirname ${output_file})" ] ; then
+if ! [ -d "$(dirname "${output_file}")" ] ; then
   umask 0022 # directory permissions should be '755'
-  mkdir -p "$(dirname ${output_file})"
+  mkdir -p "$(dirname "${output_file}")"
 fi
 
 # assume safe defaults
@@ -85,9 +85,9 @@ chmod a-w "${output_file}"
 if [ -r "${NGCPCTL_MAIN}/templates/${output_file}.postbuild" ] ; then
   log_info "Executing postbuild for ${output_file}"
   bash "${NGCPCTL_MAIN}/templates/${output_file}.postbuild"
-elif [ -r "${NGCPCTL_MAIN}/templates/$(dirname ${output_file})/ngcpcfg.postbuild" ] ; then
+elif [ -r "${NGCPCTL_MAIN}/templates/$(dirname "${output_file}")/ngcpcfg.postbuild" ] ; then
   log_info "Executing postbuild for ${output_file}"
-  bash "${NGCPCTL_MAIN}/templates/$(dirname ${output_file})/ngcpcfg.postbuild"
+  bash "${NGCPCTL_MAIN}/templates/$(dirname "${output_file}")/ngcpcfg.postbuild"
 fi
 
 exit $RC
diff --git a/helper/check-for-mysql b/helper/check-for-mysql
index c49b0b73..dc8a3f11 100755
--- a/helper/check-for-mysql
+++ b/helper/check-for-mysql
@@ -12,7 +12,7 @@ if [ "$MYSQLID" = "2" ] ; then
   SUFF="2"
 fi
 
-if ! [ $COUNT -ge 0 2>/dev/null ] ; then
+if [ $COUNT -le 0 ] ; then
   echo "Usage: $0 <number_of_seconds> [<mysqlid>]" >&2
   exit 1
 fi
@@ -31,14 +31,17 @@ mysqld_get_param() {
 }
 
 mysqld_status () {
-  ping_output=$(/usr/bin/mysqladmin --defaults-group-suffix=$SUFF \
-    --defaults-file=/etc/mysql/debian.cnf ping 2>&1)
-  ping_alive=$(( ! $? ))
+  if /usr/bin/mysqladmin --defaults-group-suffix=$SUFF \
+    --defaults-file=/etc/mysql/debian.cnf ping 2>&1 ; then
+    ping_alive=1
+  else
+    ping_alive=0
+  fi
 
   ps_alive=0
   pidfile=$(mysqld_get_param pid-file)
 
-  if [ -f "$pidfile" ] && ps $(cat $pidfile) &>/dev/null ; then
+  if [ -f "$pidfile" ] && ps "$(cat "$pidfile")" &>/dev/null ; then
     ps_alive=1
   fi
 
@@ -51,7 +54,7 @@ mysqld_status () {
 }
 
 printf "Checking MySQL service status (for a maximum of %s seconds): " "$COUNT"
-for i in $(seq 1 $COUNT) ; do
+for _ in $(seq 1 $COUNT) ; do
   if mysqld_status check_alive warn; then
     printf "available.\n"
     exit 0
diff --git a/sbin/ngcpcfg b/sbin/ngcpcfg
index 5a455115..3b17932c 100755
--- a/sbin/ngcpcfg
+++ b/sbin/ngcpcfg
@@ -15,7 +15,7 @@ FUNCTIONS="${FUNCTIONS:-/usr/share/ngcp-ngcpcfg/functions/}"
 SCRIPTS="${SCRIPTS:-/usr/share/ngcp-ngcpcfg/scripts/}"
 
 if ! [ -r "${FUNCTIONS}/main" ] ; then
-  printf "Error: ${FUNCTIONS}/main could not be read. Exiting.\n" >&2
+  printf "Error: %s/main could not be read. Exiting.\n" "${FUNCTIONS}" >&2
   exit 1
 fi
 
@@ -29,7 +29,7 @@ if [[ "${1:-}" == "decrypt" ]] ; then
     fi
   }
 else
-  . ${FUNCTIONS}/main
+  . "${FUNCTIONS}"/main
 fi
 
 # helper functions
@@ -46,7 +46,7 @@ usage() {
   [ "${1:-}" = "1" ] && exec >&2
 
   printf "%s - Configuration Management System\n\n" "$PN"
-  printf "Usage: $PN <action> [<opts>]
+  printf "Usage: %s <action> [<opts>]
 
 Actions:
   check [<path>]      validate YAML configuration files
@@ -58,7 +58,7 @@ Actions:
   status [<opts>]     display status of configuration file
   log [<opts>]        show log of config changes
   show [<id>]         show latest config change (or <id> if specified)
-"
+" "$PN"
 
   # display only if ngcp-ngcpcfg-ha is available
   if [ -r /usr/share/ngcp-ngcpcfg/functions/ha_features ] ; then
@@ -91,9 +91,9 @@ Actions:
 }
 
 version() {
-  versinfo=$(dpkg-query -f '${Version}' -W ngcp-ngcpcfg 2>/dev/null)
+  versinfo=$(dpkg-query -f "\${Version}" -W ngcp-ngcpcfg 2>/dev/null)
   [ -n "${versinfo:-}" ] || versinfo='information not available'
-  printf "ngcpcfg, version ${versinfo}\n"
+  printf "ngcpcfg, version %s\n" "${versinfo}"
 }
 
 case ${1:-} in
diff --git a/scripts/apply b/scripts/apply
index ea44ab1e..b425fcb5 100755
--- a/scripts/apply
+++ b/scripts/apply
@@ -16,7 +16,6 @@ if ! [ -r "${FUNCTIONS}"/main ] ; then
   exit 1
 fi
 
-timestamp_replacementchars=''
 . "${FUNCTIONS}"/main
 
 # based on check_local_state() from scripts/status
diff --git a/scripts/build b/scripts/build
index b49bbc15..c04d4431 100755
--- a/scripts/build
+++ b/scripts/build
@@ -11,12 +11,12 @@ FUNCTIONS="${FUNCTIONS:-/usr/share/ngcp-ngcpcfg/functions/}"
 HELPER="${HELPER:-/usr/share/ngcp-ngcpcfg/helper/}"
 SCRIPTS="${SCRIPTS:-/usr/share/ngcp-ngcpcfg/scripts/}"
 
-if ! [ -r ${FUNCTIONS}/main ] ; then
-  printf "Error: ${FUNCTIONS}/main could not be read. Exiting.\n" >&2
+if ! [ -r "${FUNCTIONS}"/main ] ; then
+  printf "Error: %s/main could not be read. Exiting.\n" "${FUNCTIONS}" >&2
   exit 1
 fi
 
-. ${FUNCTIONS}/main
+. "${FUNCTIONS}"/main
 
 # Sanity check the YAML and schema files.
 "${SCRIPTS}"/check
@@ -33,7 +33,7 @@ killall tt2-daemon 2>/dev/null || true
 rm -f /var/run/ngcpcfg.port
 
 # Start new tt2-daemon Perl process
-${HELPER}/tt2-daemon
+"${HELPER}"/tt2-daemon
 
 # Load all the configs in proper order and check their avialability and valid YAML syntax
 for f in ${NGCPCTL_CONFIG:-} ${HOST_CONFIG:-} ${LOCAL_CONFIG:-} ${NETWORK_CONFIG:-} ${EXTRA_CONFIG_FILES:-} ${CONSTANTS_CONFIG:-} ; do
@@ -50,7 +50,7 @@ build_config_files() {
   for file in $(generate_template_list "$@") ; do
     log_debug "${HELPER}/build_config $file"
     "${HELPER}/build_config" "${file}"
-    RC=$(($RC + $?))
+    RC=$((RC + $?))
   done
 
   record_commit_id
@@ -73,7 +73,7 @@ else
 
   if [ -n "${EXTRA_CONFIG_FILES:-}" ] ; then
     for file in $EXTRA_CONFIG_FILES ; do
-      if git diff-index --name-only HEAD | grep -qe -- "$(basename $file)" ; then
+      if git diff-index --name-only HEAD | grep -qe -- "$(basename "$file")" ; then
 	log_debug "modification in EXTRA_CONFIG_FILES file $file found"
         trigger_rebuild=true
         break # no reason for further checks
@@ -82,11 +82,11 @@ else
   fi
 
   if git diff-index --name-only HEAD | grep \
-         -qe "$(basename $NGCPCTL_CONFIG)" \
-         -qe "$(basename $HOST_CONFIG)" \
-         -qe "$(basename $LOCAL_CONFIG)" \
-         -qe "$(basename $NETWORK_CONFIG)" \
-         -qe "$(basename $CONSTANTS_CONFIG)" ; then
+         -qe "$(basename "$NGCPCTL_CONFIG")" \
+         -qe "$(basename "$HOST_CONFIG")" \
+         -qe "$(basename "$LOCAL_CONFIG")" \
+         -qe "$(basename "$NETWORK_CONFIG")" \
+         -qe "$(basename "$CONSTANTS_CONFIG")" ; then
     log_debug "modification in main configuration file found"
     trigger_rebuild=true
   fi
@@ -108,9 +108,9 @@ else
 
         # drop HA file suffix of all registered nodes
         if [ -r /etc/ngcp-config/systems.cfg ] ; then
-          for host in $(cat /etc/ngcp-config/systems.cfg) ; do
-             build_file="${build_file%%.${host}}"
-           done
+          while IFS= read -r host ; do
+            build_file="${build_file%%.${host}}"
+          done < /etc/ngcp-config/systems.cfg
         fi
 
         build_file="${build_file%%.tt2}"
@@ -128,7 +128,7 @@ else
      done
 
      log_debug "Executing: build_config_files ${file_list}"
-     build_config_files ${file_list}
+     build_config_files "${file_list}"
   fi
 fi
 
diff --git a/scripts/show b/scripts/show
index 31483fd2..77e4e692 100755
--- a/scripts/show
+++ b/scripts/show
@@ -24,7 +24,7 @@ fi
 
 
 cd "$NGCPCTL_MAIN"
-git show ${git_commit}
+git show "${git_commit}"
 
 exit 0
 
diff --git a/testsuite/build-check b/testsuite/build-check
index 09f76cd7..af86f27a 100644
--- a/testsuite/build-check
+++ b/testsuite/build-check
@@ -11,19 +11,20 @@ else
   bailout() { exit 1; }
 fi
 
-export testsuite="$(dirname $PWD/$0)"
+testsuite="$(dirname "${PWD}/$0")"
+export testsuite
 
 TMPDIR="$(mktemp -d)"
 echo "Switching to temporary directory $TMPDIR"
 cd "$TMPDIR"
-cp -a ${testsuite}/* .
+cp -a "${testsuite}"/* .
 
 export FUNCTIONS="$testsuite/../functions/"
 export HELPER="$testsuite/../helper/"
 export SCRIPTS="$testsuite/../scripts/"
 
 echo -n "Testing ngcpcfg without any arguments: "
-if $testsuite/../sbin/ngcpcfg 2>&1 | grep -q "^Usage:$" ; then
+if "$testsuite"/../sbin/ngcpcfg 2>&1 | grep -q "^Usage:$" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg without any arguments" >&2
@@ -31,7 +32,7 @@ else
 fi
 
 echo -n "Testing ngcpcfg --help: "
-if $testsuite/../sbin/ngcpcfg --help 2>&1 | grep -q "^Usage:$" ; then
+if "$testsuite"/../sbin/ngcpcfg --help 2>&1 | grep -q "^Usage:$" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg --help" >&2
@@ -39,7 +40,7 @@ else
 fi
 
 echo -n "Testing ngcpcfg --version: "
-if $testsuite/../sbin/ngcpcfg --version 2>&1 | grep -q "version" ; then
+if "$testsuite"/../sbin/ngcpcfg --version 2>&1 | grep -q "version" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg --version" >&2
@@ -47,12 +48,9 @@ else
 fi
 
 echo "Testing ngcpcfg build:"
-$testsuite/../sbin/ngcpcfg build > build.log
+"$testsuite"/../sbin/ngcpcfg build > build.log
 
-oldIFS="$IFS"
-IFS="
-"
-for line in $(cat build.log) ; do
+while IFS= read -r line ; do
   case "$line" in
     Generating\ testsuite/*OK) echo generation OK ;;
     Executing\ postbuild\ for\ testsuite/*) echo postbuild OK;;
@@ -63,8 +61,7 @@ for line in $(cat build.log) ; do
      bailout
      ;;
   esac
-done
-IFS="$oldIFS"
+done < build.log
 
 # test main tt2 processing
 if [[ $(cat testsuite/testtemplate) == "foo" ]] ; then
diff --git a/testsuite/ngcp-network b/testsuite/ngcp-network
index 75e70b0e..8143e953 100644
--- a/testsuite/ngcp-network
+++ b/testsuite/ngcp-network
@@ -23,11 +23,11 @@ bailout() {
 trap bailout 1 2 3 3 6 9 14 15
 
 OK() {
-    printf "ok ${1}           ${2}\n"
+    printf "ok %s           %s\n" "$1" "$2"
 }
 
 FAIL() {
-    printf "not ok ${1}        ${2}\n"
+    printf "not ok %s        %s\n" "$1" "$2"
     RC=1
 }
 
@@ -112,7 +112,7 @@ assertEqualFiles testfiles/deployment.yml network-config/deployment.yml
 
 
 # TAP output
-printf "1..$count\n"
+printf "1..%s\n" "${count}"
 cat "$OUTPUT"
 
 bailout
diff --git a/testsuite/values-check b/testsuite/values-check
index a1526126..ad025f4c 100644
--- a/testsuite/values-check
+++ b/testsuite/values-check
@@ -11,19 +11,20 @@ else
   bailout() { exit 1; }
 fi
 
-export testsuite="$(dirname $PWD/$0)"
+testsuite="$(dirname "${PWD}/$0")"
+export testsuite
 
 TMPDIR="$(mktemp -d)"
 echo "Switching to temporary directory $TMPDIR"
 cd "$TMPDIR"
-cp -a ${testsuite}/* .
+cp -a "${testsuite}"/* .
 
 export FUNCTIONS="$testsuite/../functions/"
 export HELPER="$testsuite/../helper/"
 export SCRIPTS="$testsuite/../scripts/"
 
 echo -n "Testing ngcpcfg without any arguments: "
-if $testsuite/../sbin/ngcpcfg 2>&1 | grep -q "^Usage:$" ; then
+if "$testsuite"/../sbin/ngcpcfg 2>&1 | grep -q "^Usage:$" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg without any arguments" >&2
@@ -31,7 +32,7 @@ else
 fi
 
 echo -n "Testing ngcpcfg --help: "
-if $testsuite/../sbin/ngcpcfg --help 2>&1 | grep -q "^Usage:$" ; then
+if "$testsuite"/../sbin/ngcpcfg --help 2>&1 | grep -q "^Usage:$" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg --help" >&2
@@ -39,7 +40,7 @@ else
 fi
 
 echo -n "Testing ngcpcfg --version: "
-if $testsuite/../sbin/ngcpcfg --version 2>&1 | grep -q "version" ; then
+if "$testsuite"/../sbin/ngcpcfg --version 2>&1 | grep -q "version" ; then
   echo OK
 else
   echo "Error with executing ngcpcfg --version" >&2
@@ -47,21 +48,21 @@ else
 fi
 
 echo "Testing ngcpcfg values: database.dbhost"
-value=$($testsuite/../sbin/ngcpcfg values database.dbhost)
+value=$("$testsuite"/../sbin/ngcpcfg values database.dbhost)
 if [ "${value}" != "localhost" ] ; then
   echo "Error caught: database.dbhost != 'localhost'"
   bailout
 fi
 
 echo "Testing ngcpcfg values: ossbss.provisioning.database.user"
-value=$($testsuite/../sbin/ngcpcfg values ossbss.provisioning.database.user)
+value=$("$testsuite"/../sbin/ngcpcfg values ossbss.provisioning.database.user)
 if [ "${value}" != "soap" ] ; then
   echo "Error caught: ossbss.provisioning.database.user != 'soap'"
   bailout
 fi
 
 echo "Testing ngcpcfg values: www_admin.fees_csv.element_order"
-value=$($testsuite/../sbin/ngcpcfg values www_admin.fees_csv.element_order)
+value=$("$testsuite"/../sbin/ngcpcfg values www_admin.fees_csv.element_order)
 if [ "${value}" != "destination zone zone_detail onpeak_init_rate \
 onpeak_init_interval onpeak_follow_rate onpeak_follow_interval \
 offpeak_init_rate offpeak_init_interval offpeak_follow_rate \