diff --git a/tools/ci/cibuild.sh b/tools/ci/cibuild.sh
index 4c405ac25d..b9eb75017c 100755
--- a/tools/ci/cibuild.sh
+++ b/tools/ci/cibuild.sh
@@ -26,19 +26,19 @@
 set -e
 set -o xtrace
 
-WD=$(cd $(dirname $0) && pwd)
-WORKSPACE=$(cd $WD/../../../ && pwd -P)
-nuttx=$WORKSPACE/nuttx
-apps=$WORKSPACE/apps
-tools=$WORKSPACE/tools
-prebuilt=$WORKSPACE/prebuilt
+WD=$(cd "$(dirname "$0")" && pwd)
+WORKSPACE=$(cd "${WD}"/../../../ && pwd -P)
+nuttx=${WORKSPACE}/nuttx
+apps=${WORKSPACE}/apps
+tools=${WORKSPACE}/tools
+prebuilt=${WORKSPACE}/prebuilt
 os=$(uname -s)
 EXTRA_PATH=
 
-case $os in
+case ${os} in
   Darwin)
     install="python-tools u-boot-tools elf-toolchain gen-romfs kconfig-frontends arm-gcc-toolchain riscv-gcc-toolchain xtensa-esp32-gcc-toolchain avr-gcc-toolchain c-cache binutils"
-    mkdir -p ${prebuilt}/homebrew
+    mkdir -p "${prebuilt}"/homebrew
     export HOMEBREW_CACHE=${prebuilt}/homebrew
     # https://github.com/actions/virtual-environments/issues/2322#issuecomment-749211076
     rm -rf /usr/local/bin/2to3
@@ -51,17 +51,17 @@ case $os in
 esac
 
 function add_path {
-  PATH=$1:$PATH
-  EXTRA_PATH=$1:$EXTRA_PATH
+  PATH=$1:${PATH}
+  EXTRA_PATH=$1:${EXTRA_PATH}
 }
 
 function python-tools {
   # Python User Env
   PIP_USER=yes
   export PIP_USER
-  PYTHONUSERBASE=$prebuilt/pylocal
+  PYTHONUSERBASE=${prebuilt}/pylocal
   export PYTHONUSERBASE
-  add_path $PYTHONUSERBASE/bin
+  add_path "${PYTHONUSERBASE}"/bin
   pip3 install pexpect
 
   # MCUboot's tool for image signing and key management
@@ -72,7 +72,7 @@ function python-tools {
 
 function u-boot-tools {
   if ! type mkimage > /dev/null; then
-    case $os in
+    case ${os} in
       Darwin)
         brew install u-boot-tools
         ;;
@@ -82,7 +82,7 @@ function u-boot-tools {
 
 function elf-toolchain {
   if ! type x86_64-elf-gcc > /dev/null; then
-    case $os in
+    case ${os} in
       Darwin)
         brew install x86_64-elf-gcc
         ;;
@@ -92,70 +92,70 @@ function elf-toolchain {
 }
 
 function gen-romfs {
-  add_path $prebuilt/genromfs/usr/bin
+  add_path "${prebuilt}"/genromfs/usr/bin
 
-  if [ ! -f "$prebuilt/genromfs/usr/bin/genromfs" ]; then
-    if [ ! -d "$tools" ]; then
-      git clone https://bitbucket.org/nuttx/tools.git $tools
+  if [ ! -f "${prebuilt}/genromfs/usr/bin/genromfs" ]; then
+    if [ ! -d "${tools}" ]; then
+      git clone https://bitbucket.org/nuttx/tools.git "${tools}"
     fi
-    mkdir -p $prebuilt; cd $tools
-    tar zxf genromfs-0.5.2.tar.gz -C $prebuilt
-    cd $prebuilt/genromfs-0.5.2
-    make install PREFIX=$prebuilt/genromfs
-    cd $prebuilt
+    mkdir -p "${prebuilt}"; cd "${tools}"
+    tar zxf genromfs-0.5.2.tar.gz -C "${prebuilt}"
+    cd "${prebuilt}"/genromfs-0.5.2
+    make install PREFIX="${prebuilt}"/genromfs
+    cd "${prebuilt}"
     rm -rf genromfs-0.5.2
   fi
 }
 
 function gperf {
-  add_path $prebuilt/gperf/bin
+  add_path "${prebuilt}"/gperf/bin
 
-  if [ ! -f "$prebuilt/gperf/bin/gperf" ]; then
-    cd $prebuilt
+  if [ ! -f "${prebuilt}/gperf/bin/gperf" ]; then
+    cd "${prebuilt}"
     wget --quiet http://ftp.gnu.org/pub/gnu/gperf/gperf-3.1.tar.gz
     tar zxf gperf-3.1.tar.gz
-    cd $prebuilt/gperf-3.1
-    ./configure --prefix=$prebuilt/gperf; make; make install
-    cd $prebuilt
+    cd "${prebuilt}"/gperf-3.1
+    ./configure --prefix="${prebuilt}"/gperf; make; make install
+    cd "${prebuilt}"
     rm -rf gperf-3.1; rm gperf-3.1.tar.gz
   fi
 }
 
 function kconfig-frontends {
-  add_path $prebuilt/kconfig-frontends/bin
+  add_path "${prebuilt}"/kconfig-frontends/bin
 
-  if [ ! -f "$prebuilt/kconfig-frontends/bin/kconfig-conf" ]; then
-    cd $tools/kconfig-frontends
-    ./configure --prefix=$prebuilt/kconfig-frontends \
+  if [ ! -f "${prebuilt}/kconfig-frontends/bin/kconfig-conf" ]; then
+    cd "${tools}"/kconfig-frontends
+    ./configure --prefix="${prebuilt}"/kconfig-frontends \
       --disable-kconfig --disable-nconf --disable-qconf \
       --disable-gconf --disable-mconf --disable-static \
       --disable-shared --disable-L10n
     # Avoid "aclocal/automake missing" errors
     touch aclocal.m4 Makefile.in
     make install
-    cd $tools; git clean -xfd
+    cd "${tools}"; git clean -xfd
   fi
 }
 
 function bloaty {
-  add_path $prebuilt/bloaty/bin
-  if [ ! -f "$prebuilt/bloaty/bin/bloaty" ]; then
+  add_path "${prebuilt}"/bloaty/bin
+  if [ ! -f "${prebuilt}/bloaty/bin/bloaty" ]; then
     git clone --depth 1 --branch v1.1 https://github.com/google/bloaty bloaty-src
     cd bloaty-src
-    mkdir -p $prebuilt/bloaty
-    cmake -DCMAKE_SYSTEM_PREFIX_PATH=$prebuilt/bloaty
+    mkdir -p "${prebuilt}"/bloaty
+    cmake -DCMAKE_SYSTEM_PREFIX_PATH="${prebuilt}"/bloaty
     make install -j 6
-    cd $prebuilt
+    cd "${prebuilt}"
     rm -rf bloaty-src
   fi
 }
 
 function arm-gcc-toolchain {
-  add_path $prebuilt/gcc-arm-none-eabi/bin
+  add_path "${prebuilt}"/gcc-arm-none-eabi/bin
 
-  if [ ! -f "$prebuilt/gcc-arm-none-eabi/bin/arm-none-eabi-gcc" ]; then
+  if [ ! -f "${prebuilt}/gcc-arm-none-eabi/bin/arm-none-eabi-gcc" ]; then
     local flavor
-    case $os in
+    case ${os} in
       Darwin)
         flavor=mac
         ;;
@@ -163,7 +163,7 @@ function arm-gcc-toolchain {
         flavor=x86_64-linux
         ;;
     esac
-    cd $prebuilt
+    cd "${prebuilt}"
     wget --quiet https://developer.arm.com/-/media/Files/downloads/gnu-rm/9-2019q4/RC2.1/gcc-arm-none-eabi-9-2019-q4-major-${flavor}.tar.bz2
     tar jxf gcc-arm-none-eabi-9-2019-q4-major-${flavor}.tar.bz2
     mv gcc-arm-none-eabi-9-2019-q4-major gcc-arm-none-eabi
@@ -173,21 +173,21 @@ function arm-gcc-toolchain {
 }
 
 function mips-gcc-toolchain {
-  add_path $prebuilt/pinguino-compilers/linux64/p32/bin
+  add_path "${prebuilt}"/pinguino-compilers/linux64/p32/bin
 
-  if [ ! -f "$prebuilt/pinguino-compilers/linux64/p32/bin/p32-gcc" ]; then
-    cd $prebuilt
+  if [ ! -f "${prebuilt}/pinguino-compilers/linux64/p32/bin/p32-gcc" ]; then
+    cd "${prebuilt}"
     git clone https://github.com/PinguinoIDE/pinguino-compilers
   fi
   p32-gcc --version
 }
 
 function riscv-gcc-toolchain {
-  add_path $prebuilt/riscv64-unknown-elf-gcc/bin
+  add_path "${prebuilt}"/riscv64-unknown-elf-gcc/bin
 
-  if [ ! -f "$prebuilt/riscv64-unknown-elf-gcc/bin/riscv64-unknown-elf-gcc" ]; then
+  if [ ! -f "${prebuilt}/riscv64-unknown-elf-gcc/bin/riscv64-unknown-elf-gcc" ]; then
     local flavor
-    case $os in
+    case ${os} in
       Darwin)
         flavor=x86_64-apple-darwin
         ;;
@@ -195,7 +195,7 @@ function riscv-gcc-toolchain {
         flavor=x86_64-linux-ubuntu14
         ;;
     esac
-    cd $prebuilt
+    cd "${prebuilt}"
     wget --quiet https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.3.0-2019.08.0-${flavor}.tar.gz
     tar zxf riscv64-unknown-elf-gcc-8.3.0-2019.08.0-${flavor}.tar.gz
     mv riscv64-unknown-elf-gcc-8.3.0-2019.08.0-${flavor} riscv64-unknown-elf-gcc
@@ -205,11 +205,11 @@ function riscv-gcc-toolchain {
 }
 
 function xtensa-esp32-gcc-toolchain {
-  add_path $prebuilt/xtensa-esp32-elf/bin
+  add_path "${prebuilt}"/xtensa-esp32-elf/bin
 
-  if [ ! -f "$prebuilt/xtensa-esp32-elf/bin/xtensa-esp32-elf-gcc" ]; then
-    cd $prebuilt
-    case $os in
+  if [ ! -f "${prebuilt}/xtensa-esp32-elf/bin/xtensa-esp32-elf-gcc" ]; then
+    cd "${prebuilt}"
+    case ${os} in
       Darwin)
         wget --quiet https://dl.espressif.com/dl/xtensa-esp32-elf-gcc8_2_0-esp-2019r2-macos.tar.gz
         tar xzf xtensa-esp32-elf-gcc8_2_0-esp-2019r2-macos.tar.gz
@@ -229,7 +229,7 @@ function xtensa-esp32-gcc-toolchain {
 
 function avr-gcc-toolchain {
   if ! type avr-gcc > /dev/null; then
-    case $os in
+    case ${os} in
       Darwin)
         brew tap osx-cross/avr
         brew install avr-gcc
@@ -239,14 +239,14 @@ function avr-gcc-toolchain {
 }
 
 function rx-gcc-toolchain {
-  add_path $prebuilt/renesas-toolchain/rx-elf-gcc/bin
+  add_path "${prebuilt}"/renesas-toolchain/rx-elf-gcc/bin
 
-  if [ ! -f "$prebuilt/renesas-toolchain/rx-elf-gcc/bin/rx-elf-gcc" ]; then
-    case $os in
+  if [ ! -f "${prebuilt}/renesas-toolchain/rx-elf-gcc/bin/rx-elf-gcc" ]; then
+    case ${os} in
       Linux)
         # Download toolchain source code
         # RX toolchain is built from source code. Once prebuilt RX toolchain is made available, the below code snippet can be removed.
-        mkdir -p $prebuilt/renesas-tools/rx/source; cd $prebuilt/renesas-tools/rx/source
+        mkdir -p "${prebuilt}"/renesas-tools/rx/source; cd "${prebuilt}"/renesas-tools/rx/source
         wget --quiet https://gcc-renesas.com/downloads/d.php?f=rx/binutils/4.8.4.201803-gnurx/rx_binutils2.24_2018Q3.tar.gz \
           -O rx_binutils2.24_2018Q3.tar.gz
         tar zxf rx_binutils2.24_2018Q3.tar.gz
@@ -258,30 +258,30 @@ function rx-gcc-toolchain {
         tar zxf rx_newlib2.2.0_2018Q3.tar.gz
 
         # Install binutils
-        cd $prebuilt/renesas-tools/rx/source/binutils; chmod +x ./configure ./mkinstalldirs
-        mkdir -p $prebuilt/renesas-tools/rx/build/binutils; cd $prebuilt/renesas-tools/rx/build/binutils
-        $prebuilt/renesas-tools/rx/source/binutils/configure --target=rx-elf --prefix=$prebuilt/renesas-toolchain/rx-elf-gcc \
+        cd "${prebuilt}"/renesas-tools/rx/source/binutils; chmod +x ./configure ./mkinstalldirs
+        mkdir -p "${prebuilt}"/renesas-tools/rx/build/binutils; cd "${prebuilt}"/renesas-tools/rx/build/binutils
+        "${prebuilt}"/renesas-tools/rx/source/binutils/configure --target=rx-elf --prefix="${prebuilt}"/renesas-toolchain/rx-elf-gcc \
           --disable-werror
         make; make install
 
         # Install gcc
-        cd $prebuilt/renesas-tools/rx/source/gcc
+        cd "${prebuilt}"/renesas-tools/rx/source/gcc
         chmod +x ./contrib/download_prerequisites ./configure ./move-if-change ./libgcc/mkheader.sh
         ./contrib/download_prerequisites
         sed -i '1s/^/@documentencoding ISO-8859-1\n/' ./gcc/doc/gcc.texi
         sed -i 's/@tex/\n&/g' ./gcc/doc/gcc.texi && sed -i 's/@end tex/\n&/g' ./gcc/doc/gcc.texi
-        mkdir -p $prebuilt/renesas-tools/rx/build/gcc; cd $prebuilt/renesas-tools/rx/build/gcc
-        $prebuilt/renesas-tools/rx/source/gcc/configure --target=rx-elf --prefix=$prebuilt/renesas-toolchain/rx-elf-gcc \
+        mkdir -p "${prebuilt}"/renesas-tools/rx/build/gcc; cd "${prebuilt}"/renesas-tools/rx/build/gcc
+        "${prebuilt}"/renesas-tools/rx/source/gcc/configure --target=rx-elf --prefix="${prebuilt}"/renesas-toolchain/rx-elf-gcc \
         --disable-shared --disable-multilib --disable-libssp --disable-libstdcxx-pch --disable-werror --enable-lto \
         --enable-gold --with-pkgversion=GCC_Build_1.02 --with-newlib --enable-languages=c
         make; make install
 
         # Install newlib
-        cd $prebuilt/renesas-tools/rx/source/newlib; chmod +x ./configure
-        mkdir -p $prebuilt/renesas-tools/rx/build/newlib; cd $prebuilt/renesas-tools/rx/build/newlib
-        $prebuilt/renesas-tools/rx/source/newlib/configure --target=rx-elf --prefix=$prebuilt/renesas-toolchain/rx-elf-gcc
+        cd "${prebuilt}"/renesas-tools/rx/source/newlib; chmod +x ./configure
+        mkdir -p "${prebuilt}"/renesas-tools/rx/build/newlib; cd "${prebuilt}"/renesas-tools/rx/build/newlib
+        "${prebuilt}"/renesas-tools/rx/source/newlib/configure --target=rx-elf --prefix="${prebuilt}"/renesas-toolchain/rx-elf-gcc
         make; make install
-        rm -rf $prebuilt/renesas-tools/
+        rm -rf "${prebuilt}"/renesas-tools/
         ;;
     esac
   fi
@@ -289,55 +289,55 @@ function rx-gcc-toolchain {
 }
 
 function c-cache {
-  add_path $prebuilt/ccache/bin
+  add_path "${prebuilt}"/ccache/bin
 
   if ! type ccache > /dev/null; then
-    case $os in
+    case ${os} in
       Darwin)
         brew install ccache
         ;;
       Linux)
-        cd $prebuilt;
+        cd "${prebuilt}";
         wget https://github.com/ccache/ccache/releases/download/v3.7.7/ccache-3.7.7.tar.gz
         tar zxf ccache-3.7.7.tar.gz
-        cd ccache-3.7.7; ./configure --prefix=$prebuilt/ccache; make; make install
-        cd $prebuilt; rm -rf ccache-3.7.7; rm ccache-3.7.7.tar.gz
+        cd ccache-3.7.7; ./configure --prefix="${prebuilt}"/ccache; make; make install
+        cd "${prebuilt}"; rm -rf ccache-3.7.7; rm ccache-3.7.7.tar.gz
         ;;
     esac
   fi
 
   ccache --version
-  mkdir -p $prebuilt/ccache/bin/
-  ln -sf `which ccache` $prebuilt/ccache/bin/x86_64-elf-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/x86_64-elf-g++
-  ln -sf `which ccache` $prebuilt/ccache/bin/cc
-  ln -sf `which ccache` $prebuilt/ccache/bin/c++
-  ln -sf `which ccache` $prebuilt/ccache/bin/clang
-  ln -sf `which ccache` $prebuilt/ccache/bin/clang++
-  ln -sf `which ccache` $prebuilt/ccache/bin/gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/g++
-  ln -sf `which ccache` $prebuilt/ccache/bin/arm-none-eabi-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/arm-none-eabi-g++
-  ln -sf `which ccache` $prebuilt/ccache/bin/p32-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/riscv64-unknown-elf-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/riscv64-unknown-elf-g++
-  ln -sf `which ccache` $prebuilt/ccache/bin/xtensa-esp32-elf-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/avr-gcc
-  ln -sf `which ccache` $prebuilt/ccache/bin/avr-g++
+  mkdir -p "${prebuilt}"/ccache/bin/
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/x86_64-elf-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/x86_64-elf-g++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/cc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/c++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/clang
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/clang++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/g++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/arm-none-eabi-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/arm-none-eabi-g++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/p32-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/riscv64-unknown-elf-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/riscv64-unknown-elf-g++
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/xtensa-esp32-elf-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/avr-gcc
+  ln -sf "$(which ccache)" "${prebuilt}"/ccache/bin/avr-g++
 }
 
 function binutils {
-  mkdir -p $prebuilt/bintools/bin
-  add_path $prebuilt/bintools/bin
+  mkdir -p "${prebuilt}"/bintools/bin
+  add_path "${prebuilt}"/bintools/bin
 
   if ! type objcopy > /dev/null; then
-    case $os in
+    case ${os} in
       Darwin)
         brew install binutils
         # It is possible we cached prebuilt but did brew install so recreate
         # simlink if it exists
-        rm -f $prebuilt/bintools/bin/objcopy
-        ln -s /usr/local/opt/binutils/bin/objcopy $prebuilt/bintools/bin/objcopy
+        rm -f "${prebuilt}"/bintools/bin/objcopy
+        ln -s /usr/local/opt/binutils/bin/objcopy "${prebuilt}"/bintools/bin/objcopy
         ;;
     esac
   fi
@@ -368,19 +368,19 @@ function enable_ccache {
 
 function setup_repos {
   pushd .
-  if [ -d "$nuttx" ]; then
-    cd $nuttx; git pull
+  if [ -d "${nuttx}" ]; then
+    cd "${nuttx}"; git pull
   else
-    git clone https://github.com/apache/incubator-nuttx.git $nuttx
-    cd $nuttx
+    git clone https://github.com/apache/incubator-nuttx.git "${nuttx}"
+    cd "${nuttx}"
   fi
   git log -1
 
-  if [ -d "$apps" ]; then
-    cd $apps; git pull
+  if [ -d "${apps}" ]; then
+    cd "${apps}"; git pull
   else
-    git clone https://github.com/apache/incubator-nuttx-apps.git $apps
-    cd $apps
+    git clone https://github.com/apache/incubator-nuttx-apps.git "${apps}"
+    cd "${apps}"
   fi
   git log -1
   popd
@@ -388,30 +388,30 @@ function setup_repos {
 
 function install_tools {
   pushd .
-  for func in $install; do
-    $func
+  for func in ${install}; do
+    ${func}
   done
   popd
 
-  echo PATH=$EXTRA_PATH\$PATH > $prebuilt/env.sh
+  echo PATH="${EXTRA_PATH}"/"${PATH}" > "${prebuilt}"/env.sh
 }
 
 function run_builds {
   local ncpus
 
-  case $os in
+  case ${os} in
     Darwin)
       ncpus=$(sysctl -n hw.ncpu)
       ;;
     Linux)
-      ncpus=`grep -c ^processor /proc/cpuinfo`
+      ncpus=$(grep -c ^processor /proc/cpuinfo)
       ;;
   esac
 
-  options+="-j $ncpus"
+  options+="-j ${ncpus}"
 
-  for build in $builds; do
-    $nuttx/tools/testbuild.sh $options -e "-Wno-cpp -Werror" $build
+  for build in "${builds[@]}"; do
+    "${nuttx}"/tools/testbuild.sh ${options} -e "-Wno-cpp -Werror" "${build}"
   done
 }
 
@@ -419,7 +419,7 @@ if [ -z "$1" ]; then
    usage
 fi
 
-while [ ! -z "$1" ]; do
+while [ -n "$1" ]; do
   case "$1" in
   -h )
     usage
@@ -437,7 +437,7 @@ while [ ! -z "$1" ]; do
     options+="$1 "
     ;;
   * )
-    builds=$@
+    builds=( "$@" )
     break
     ;;
   esac