Polish "Fix shellcheck warnings in CLI's bash script"

Closes gh-11458

spring-boot-project/spring-boot-cli/src/main/executablecontent/bin/spring

@@ -36,14 +36,14 @@ if [ -z "${JAVA_HOME}" ]; then
 			export JAVA_HOME="/System/Library/Frameworks/JavaVM.framework/Home"
 		fi
 	else
-		javaExecutable="$(which javac)"
+		javaExecutable="$(command -v javac)"
 		if [[ -z "$javaExecutable" || "$(expr "${javaExecutable}" : '\([^ ]*\)')" = "no" ]]; then
 			echo "JAVA_HOME not set and cannot find javac to deduce location, please set JAVA_HOME."
 			exit 1
 		fi
 		# readlink(1) is not available as standard on Solaris 10.
-		readLink=(which readlink)
-		[ $(expr "$readLink" : '\([^ ]*\)') = "no" ] && {
+		readLink="$(command -v readlink)"
+		[ "$(expr "${readLink}" : '\([^ ]*\)')" = "no" ] && {
 			echo "JAVA_HOME not set and readlink not available, please set JAVA_HOME."
 			exit 1
 		}
@@ -74,23 +74,23 @@ fi
 
 # Attempt to find SPRING_HOME if not already set
 if [ -z "${SPRING_HOME}" ]; then
-    # Resolve links: $0 may be a link
-    PRG="$0"
-    # Need this for relative symlinks.
-    while [ -h "$PRG" ] ; do
-	    ls=$(ls -ld "$PRG")
-	    link=$(expr "$ls" : '.*-> \(.*\)$')
-	    if expr "$link" : '/.*' > /dev/null; then
-		    PRG="$link"
-	    else
-		    PRG=$(dirname "$PRG")"/$link"
-	    fi
-    done
-    SAVED="$(pwd)"
-    cd "$(dirname "${PRG}")/../" >&-
-    SPRING_HOME="$(pwd -P)"
-    export SPRING_HOME
-    cd "$SAVED" >&-
+	# Resolve links: $0 may be a link
+	PRG="$0"
+	# Need this for relative symlinks.
+	while [ -h "$PRG" ] ; do
+		ls=$(ls -ld "$PRG")
+		link=$(expr "$ls" : '.*-> \(.*\)$')
+		if expr "$link" : '/.*' > /dev/null; then
+			PRG="$link"
+		else
+			PRG=$(dirname "$PRG")"/$link"
+		fi
+	done
+	SAVED="$(pwd)"
+	cd "$(dirname "${PRG}")/../" >&- || exit 1
+	SPRING_HOME="$(pwd -P)"
+	export SPRING_HOME
+	cd "$SAVED" >&- || exit 1
 fi
 
 if [ ! -d "${SPRING_HOME}" ]; then
@@ -103,7 +103,7 @@ CLASSPATH=.:${SPRING_HOME}/bin
 if [ -d "${SPRING_HOME}/ext" ]; then
 	CLASSPATH=$CLASSPATH:${SPRING_HOME}/ext
 fi
-for f in ${SPRING_HOME}/lib/*; do
+for f in "${SPRING_HOME}"/lib/*; do
 	CLASSPATH=$CLASSPATH:$f
 done
 
@@ -112,4 +112,5 @@ if $cygwin; then
 	CLASSPATH=$(cygpath --path --mixed "$CLASSPATH")
 fi
 
-"${JAVA_HOME}/bin/java" ${JAVA_OPTS} -cp "$CLASSPATH" org.springframework.boot.loader.JarLauncher "$@"
+IFS=" " read -r -a javaOpts <<< "$JAVA_OPTS"
+"${JAVA_HOME}/bin/java" "${javaOpts[@]}" -cp "$CLASSPATH" org.springframework.boot.loader.JarLauncher "$@"