Fix shellcheck issues on startup script

fixes #470
also fixes some other quoting issues and improves vmArgs handling

Author: maths22

src/main/resources/linux/startup.sh.vtl

@@ -1,4 +1,3 @@
-#set ($vmArgs = $StringUtils.join($info.vmArgs, " "))
 #!/usr/bin/env bash
 # GNU/Linux startup script generated by JavaPackager plugin
 
@@ -11,7 +10,7 @@ function showMessage() {
 	if type -p notify-send; then
 		notify-send -u critical "${info.name}" "$1"
 	else
-		echo $1
+		echo "$1"
 	fi
 }
 if type -p java > /dev/null; then
@@ -45,8 +44,7 @@ function compareVersions() {
         return 0
 }
 JAVA_VERSION=$("$JAVA" -version 2>&1 | awk -F '"' '/version/ {print $2}')
-compareVersions "$JAVA_VERSION" "${info.jreMinVersion}"
-if [[ $? != 0 ]]; then
+if ! compareVersions "$JAVA_VERSION" "${info.jreMinVersion}"; then
     showMessage "The application requires a Java Runtime Environment ${info.jreMinVersion} or higher."
     exit 1
 fi
@@ -63,17 +61,21 @@ BINARY="$SCRIPTPATH/${info.jarFile.name}"
 export PATH=${info.envPath}
 #end
 
-JVMDefaultOptions="${vmArgs}"
+JVMDefaultOptions=()
+#foreach ($vmArg in $info.vmArgs)
+JVMDefaultOptions+=("$vmArg")
+#end
+
 JVMOptionsFile="$SCRIPTPATH/${info.name}.l4j.ini"
-[ -f "${JVMOptionsFile}" ] && while read -r option; do JVMDefaultOptions+=" $option"; done <<< $(sed "/^#.*$/d" "${JVMOptionsFile}")
+[ -f "${JVMOptionsFile}" ] && while read -r -a option; do JVMDefaultOptions+=("${option[@]}"); done <<< "$(sed -e "/^#.*$/d" -e "/^[[:space:]]*$/d" "${JVMOptionsFile}")"
 
 JVMClassPath="$BINARY"
 #foreach ($classpath in $info.classpaths)
 JVMClassPath+=":${classpath}"
 #end
 
 #if ($info.useResourcesAsWorkingDir)
-cd "$SCRIPTPATH"
+cd "$SCRIPTPATH" || exit 1
 #end
 
 #if ($info.scripts.bootstrap)
@@ -82,8 +84,8 @@ Bootstrap="$SCRIPTPATH/scripts/${info.bootstrapFile.name}" && [ -x "$Bootstrap"
 #end
 
 #if ($info.administratorRequired)
-pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY GDKBACKEND=x11 "${JAVA}" ${JVMDefaultOptions} -jar "${JVMClassPath}" $@
+pkexec env DISPLAY="$DISPLAY" XAUTHORITY="$XAUTHORITY" GDKBACKEND=x11 "${JAVA}" "${JVMDefaultOptions[@]}" -jar "${JVMClassPath}" "$@"
 #else
-"${JAVA}" ${JVMDefaultOptions} -jar "${JVMClassPath}" $@
+"${JAVA}" "${JVMDefaultOptions[@]}" -jar "${JVMClassPath}" "@"
 #end
 exit 0