diff --git a/build.sh b/build.sh
index a63b327624..bf3c3c15a9 100755
--- a/build.sh
+++ b/build.sh
@@ -15,32 +15,32 @@ set -e # exit at first error
 
 board=$1
 target=${*:2}
-cd $(dirname $0)
+cd "$(dirname "$0")"
 basedir=$(pwd)
 gzip=$(which pigz 2> /dev/null || which gzip 2> /dev/null)
 
 # extra environment from local file
-test -f $basedir/.build-env && source $basedir/.build-env
+test -f "$basedir/.build-env" && source "$basedir/.build-env"
 
 # OS name
 if [ -n "$THINGOS_SHORT_NAME" ]; then
     osname=$THINGOS_SHORT_NAME
 else
-    osname=$(source $basedir/board/common/overlay/etc/version && echo $OS_SHORT_NAME)
+    osname=$(source "$basedir/board/common/overlay/etc/version" && echo "$OS_SHORT_NAME")
 fi
 
 # OS version
 if [ -n "$THINGOS_VERSION" ]; then
     osversion=$THINGOS_VERSION
 else
-    osversion=$(source $basedir/board/common/overlay/etc/version && echo $OS_VERSION)
+    osversion=$(source "$basedir/board/common/overlay/etc/version" && echo "$OS_VERSION")
 fi
 
 # when the special "boards" keyword is used for board, simply list all known boards
 if [ "$board" == "boards" ]; then
-    boards=$(ls $basedir/configs/*_defconfig | grep -v initramfs | grep -oE '\w+_defconfig$' | cut -d '_' -f 1)
+    boards=$(ls "$basedir"/configs/*_defconfig | grep -v initramfs | grep -oE '\w+_defconfig$' | cut -d '_' -f 1)
     for b in $boards; do
-        echo $b
+        echo "$b"
     done
 
     exit 0
@@ -48,9 +48,9 @@ fi
 
 # when the special "all" keyword is used for board, all boards are processed, in turn
 if [ "$board" == "all" ]; then
-    boards=$(ls $basedir/configs/*_defconfig | grep -v initramfs | grep -oE '\w+_defconfig$' | cut -d '_' -f 1)
+    boards=$(ls "$basedir"/configs/*_defconfig | grep -v initramfs | grep -oE '\w+_defconfig$' | cut -d '_' -f 1)
     for b in $boards; do
-        if ! $0 $b $target; then
+        if ! $0 "$b" "$target"; then
             exit 1
         fi
     done
@@ -61,96 +61,96 @@ fi
 outputdir=$basedir/output/$board
 boarddir=$basedir/board/$board
 
-if ! [ -f $basedir/configs/${board}_defconfig ]; then
+if ! [ -f "$basedir/configs/${board}_defconfig" ]; then
     echo "unknown board: $board"
     exit 1
 fi
 
 function prepare_target_dir() {
-    if [ -L $outputdir/target/var/lib ]; then
-        rm $outputdir/target/var/lib
-        mkdir $outputdir/target/var/lib
+    if [ -L "$outputdir/target/var/lib" ]; then
+        rm "$outputdir/target/var/lib"
+        mkdir "$outputdir/target/var/lib"
     fi
 }
 
-mkdir -p $outputdir
+mkdir -p "$outputdir"
 
-if ! [ -f $outputdir/.config ]; then
-    make O=$outputdir ${board}_defconfig
+if ! [ -f "$outputdir/.config" ]; then
+    make O="$outputdir" "${board}_defconfig"
 fi
 
 if [ "$target" == "mkimage" ]; then
-    $boarddir/mkimage.sh
+    "$boarddir/mkimage.sh"
 
 elif [ "$target" == "mkrelease" ]; then
-    test -f $outputdir/images/$osname-$board.img || $boarddir/mkimage.sh
-    cp $outputdir/images/$osname-$board.img $outputdir/images/$osname-$board-$osversion.img
+    test -f "$outputdir/images/$osname-$board.img" || "$boarddir/mkimage.sh"
+    cp "$outputdir/images/$osname-$board.img" "$outputdir/images/$osname-$board-$osversion.img"
     
     echo "preparing compressed xz image"
-    rm -f $outputdir/images/$osname-$board-$osversion.img.xz
-    xz -6ek -T 0 $outputdir/images/$osname-$board-$osversion.img
+    rm -f "$outputdir/images/$osname-$board-$osversion.img.xz"
+    xz -6ek -T 0 "$outputdir/images/$osname-$board-$osversion.img"
     echo "your xz image is ready at $outputdir/images/$osname-$board-$osversion.img.xz"
     
     echo "preparing compressed gz image"
-    rm -f $outputdir/images/$osname-$board-$osversion.img.gz
-    $gzip $outputdir/images/$osname-$board-$osversion.img
+    rm -f "$outputdir/images/$osname-$board-$osversion.img.gz"
+    $gzip "$outputdir/images/$osname-$board-$osversion.img"
     echo "your gz image is ready at $outputdir/images/$osname-$board-$osversion.img.gz"
     
-    rm -f $outputdir/images/$osname-$board-$osversion.img
+    rm -f "$outputdir/images/$osname-$board-$osversion.img"
 
 elif [ "$target" == "clean-target" ]; then
-    if [ -d $outputdir/target ]; then
+    if [ -d "$outputdir/target" ]; then
         echo "removing target directory"
-        rm -rf $outputdir/target/*
+        rm -rf "$outputdir/target/"*
 
         echo "removing staging directory"
-        rm -rf $outputdir/staging/*
+        rm -rf "$outputdir/staging/"*
 
         echo "removing images directory"
-        rm -rf $outputdir/images/*
+        rm -rf "$outputdir/images/"*
     fi
 
-    if [ -d $outputdir/build ]; then
+    if [ -d "$outputdir/build" ]; then
         echo "removing .stamp_target_installed files"
-        find $outputdir/build -name .stamp_target_installed | xargs -r rm
+        find "$outputdir/build" -name .stamp_target_installed -print0 | xargs -0 -r rm
 
         echo "removing .stamp_staging_installed files"
-        find $outputdir/build -name .stamp_staging_installed | xargs -r rm
+        find "$outputdir/build" -name .stamp_staging_installed -print0 | xargs -0 -r rm
 
         echo "removing .stamp_host_installed files"
-        find $outputdir/build -name .stamp_host_installed | xargs -r rm
+        find "$outputdir/build" -name .stamp_host_installed -print0 | xargs -0 -r rm
 
         echo "removing .stamp_images_installed files"
-        find $outputdir/build -name .stamp_images_installed | xargs -r rm
+        find "$outputdir/build" -name .stamp_images_installed -print0 | xargs -0 -r rm
 
         echo "removing linux kernel build dir"
-        make O=$outputdir linux-dirclean
+        make O="$outputdir" linux-dirclean
     fi
 
-    if [ -f $outputdir/.config ]; then
+    if [ -f "$outputdir/.config" ]; then
         echo "removing .config file"
-        rm -f $outputdir/.config
+        rm -f "$outputdir/.config"
     fi
 
     echo "target is clean"
 
 elif [[ "$target" == initramfs* ]]; then
     extra_args=${target:10}
-    $0 ${board}_initramfs $extra_args
-    if [ -z "$extra_args" ] && [ -x $boarddir/cpinitramfs.sh ]; then
-        IMG_DIR=$basedir/output/${board}_initramfs/images/ BOARD_DIR=$boarddir $boarddir/cpinitramfs.sh
+    $0 "${board}_initramfs" "$extra_args"
+    if [ -z "$extra_args" ] && [ -x "$boarddir/cpinitramfs.sh" ]; then
+        IMG_DIR=$basedir/output/${board}_initramfs/images/ BOARD_DIR=$boarddir "$boarddir/cpinitramfs.sh"
     fi
 
 elif [ "$target" == "all" ]; then
     prepare_target_dir
-    make O=$outputdir all
+    make O="$outputdir" all
 
 elif [ -n "$target" ]; then
     prepare_target_dir
-    make O=$outputdir $target
+    make O="$outputdir" "$target"
 
 else  # if [ -z "$target ]
-    $0 $board all
+    $0 "$board" all
     echo "build successful"
 fi