Silence shellcheck warnings (RPi-Distro#255)

* Made more specific shellcheck disables
* Fixed variable quoting (SC2086,SC2064)
* Use `$*` expansion instead of `$@` when not using arrays (SC2124)
* Use cleaner `$()` syntax instead of back quotes (SC2006)
* Improved comparator (SC2166)
* Minor improvements in coding style

Tested clean output using: `find -name "*.sh" | xargs -n1 shellcheck -x`.

build-docker.sh

@@ -1,11 +1,10 @@
 #!/bin/bash -e
 
-BUILD_OPTS="$@"
+BUILD_OPTS="$*"
 
 DOCKER="docker"
 set +e
-$DOCKER ps >/dev/null 2>&1
-if [ $? != 0 ]; then
+if ! $DOCKER ps >/dev/null 2>&1; then
 	DOCKER="sudo docker"
 fi
 if ! $DOCKER ps >/dev/null; then
@@ -23,8 +22,11 @@ while getopts "c:" flag
 do
 	case "$flag" in
 		c)
+			# shellcheck disable=SC1090
 			source "$OPTARG"
 			;;
+		*)
+			;;
 	esac
 done
 
@@ -53,7 +55,7 @@ fi
 
 $DOCKER build -t pi-gen .
 if [ "$CONTAINER_EXISTS" != "" ]; then
-	trap "echo 'got CTRL+C... please wait 5s'; $DOCKER stop -t 5 ${CONTAINER_NAME}_cont" SIGINT SIGTERM
+	trap 'echo "got CTRL+C... please wait 5s"; $DOCKER stop -t 5 ${CONTAINER_NAME}_cont' SIGINT SIGTERM
 	time $DOCKER run --rm --privileged \
 		--volumes-from="${CONTAINER_NAME}" --name "${CONTAINER_NAME}_cont" \
 		pi-gen \
@@ -62,7 +64,7 @@ if [ "$CONTAINER_EXISTS" != "" ]; then
 	rsync -av work/*/build.log deploy/" &
 	wait "$!"
 else
-	trap "echo 'got CTRL+C... please wait 5s'; $DOCKER stop -t 5 ${CONTAINER_NAME}" SIGINT SIGTERM
+	trap 'echo "got CTRL+C... please wait 5s"; $DOCKER stop -t 5 ${CONTAINER_NAME}' SIGINT SIGTERM
 	time $DOCKER run --name "${CONTAINER_NAME}" --privileged \
 		pi-gen \
 		bash -e -o pipefail -c "dpkg-reconfigure qemu-user-static &&
@@ -76,7 +78,7 @@ ls -lah deploy
 
 # cleanup
 if [ "$PRESERVE_CONTAINER" != "1" ]; then
-	$DOCKER rm -v $CONTAINER_NAME
+	$DOCKER rm -v "$CONTAINER_NAME"
 fi
 
 echo "Done! Your image(s) should be in deploy/"

build.sh

@@ -1,5 +1,5 @@
 #!/bin/bash -e
-# shellcheck disable=SC2119,SC1091
+# shellcheck disable=SC2119
 run_sub_stage()
 {
 	log "Begin ${SUB_STAGE_DIR}"
@@ -102,7 +102,7 @@ run_stage(){
 			./prerun.sh
 			log "End ${STAGE_DIR}/prerun.sh"
 		fi
-		for SUB_STAGE_DIR in ${STAGE_DIR}/*; do
+		for SUB_STAGE_DIR in "${STAGE_DIR}"/*; do
 			if [ -d "${SUB_STAGE_DIR}" ] &&
 			   [ ! -f "${SUB_STAGE_DIR}/SKIP" ]; then
 				run_sub_stage
@@ -124,6 +124,7 @@ fi
 
 
 if [ -f config ]; then
+	# shellcheck disable=SC1091
 	source config
 fi
 
@@ -132,8 +133,11 @@ do
 	case "$flag" in
 		c)
 			EXTRA_CONFIG="$OPTARG"
+			# shellcheck disable=SC1090
 			source "$EXTRA_CONFIG"
 			;;
+		*)
+			;;
 	esac
 done
 
@@ -206,8 +210,8 @@ log "Begin ${BASE_DIR}"
 
 STAGE_LIST=${STAGE_LIST:-${BASE_DIR}/stage*}
 
-for STAGE_DIR_ in $STAGE_LIST; do
-	STAGE_DIR=`realpath "${STAGE_DIR_}"`
+for STAGE_DIR in $STAGE_LIST; do
+	STAGE_DIR=$(realpath "${STAGE_DIR}")
 	run_stage
 done
 

export-noobs/00-release/files/partition_setup.sh

@@ -3,6 +3,7 @@
 
 set -ex
 
+# shellcheck disable=SC2154
 if [ -z "$part1" ] || [ -z "$part2" ]; then
   printf "Error: missing environment variable part1 or part2\n" 1>&2
   exit 1
@@ -17,7 +18,8 @@ sed /tmp/1/cmdline.txt -i -e "s|root=[^ ]*|root=${part2}|"
 sed /tmp/2/etc/fstab -i -e "s|^[^#].* / |${part2}  / |"
 sed /tmp/2/etc/fstab -i -e "s|^[^#].* /boot |${part1}  /boot |"
 
-if [ -z $restore ]; then
+# shellcheck disable=SC2154
+if [ -z "$restore" ]; then
   if [ -f /mnt/ssh ]; then
     cp /mnt/ssh /tmp/1/
   fi

stage2/02-net-tweaks/01-run.sh

@@ -23,13 +23,11 @@ systemctl disable hostapd
 systemctl disable dnsmasq
 EOF
 
-if [ -v WPA_COUNTRY ]
-then
+if [ -v WPA_COUNTRY ]; then
 	echo "country=${WPA_COUNTRY}" >> "${ROOTFS_DIR}/etc/wpa_supplicant/wpa_supplicant.conf"
 fi
 
-if [ -v WPA_ESSID -a -v WPA_PASSWORD ]
-then
+if [ -v WPA_ESSID ] && [ -v WPA_PASSWORD ]; then
 on_chroot <<EOF
 wpa_passphrase "${WPA_ESSID}" "${WPA_PASSWORD}" >> "/etc/wpa_supplicant/wpa_supplicant.conf"
 EOF