Update READMEs: Use consistent formatting for environment variables

Author: szarnyasg

README.md

@@ -52,15 +52,15 @@ To place Spark under `/opt/`:
 ```bash
 curl https://archive.apache.org/dist/spark/spark-3.2.2/spark-3.2.2-bin-hadoop3.2.tgz | sudo tar -xz -C /opt/
 export SPARK_HOME="/opt/spark-3.2.2-bin-hadoop3.2"
-export PATH="$SPARK_HOME/bin":"$PATH"
+export PATH="${SPARK_HOME}/bin":"${PATH}"
 ```
 
 To place under `~/`:
 
 ```bash
 curl https://archive.apache.org/dist/spark/spark-3.2.2/spark-3.2.2-bin-hadoop3.2.tgz | tar -xz -C ~/
 export SPARK_HOME=~/spark-3.2.2-bin-hadoop3.2
-export PATH="$SPARK_HOME/bin":"$PATH"
+export PATH="${SPARK_HOME}/bin":"${PATH}"
 ```
 
 Both Java 8 and Java 11 are supported.
@@ -185,7 +185,7 @@ The `ldbc/datagen-jar` image contains the assembly JAR, so it can bundled in you
 ```docker
 FROM my-spark-image
 ARG VERSION
-COPY --from=ldbc/datagen-jar:$VERSION /jar /lib/ldbc-datagen.jar
+COPY --from=ldbc/datagen-jar:${VERSION} /jar /lib/ldbc-datagen.jar
 ```
 
 The JAR-only Docker image can be built with the provided Dockerfile. To build, execute the following command from the repository directory:

tools/emr/README.md

@@ -35,7 +35,7 @@ export PLATFORM_VERSION=$(sbt -batch -error 'print platformVersion')
 export DATAGEN_VERSION=$(sbt -batch -error 'print version')
 export LDBC_SNB_DATAGEN_JAR=$(sbt -batch -error 'print assembly / assemblyOutputPath')
 export JAR_NAME=$(basename ${LDBC_SNB_DATAGEN_JAR})
-aws s3 cp ${LDBC_SNB_DATAGEN_JAR} s3://${BUCKET_NAME}/jars/$JAR_NAME
+aws s3 cp ${LDBC_SNB_DATAGEN_JAR} s3://${BUCKET_NAME}/jars/${JAR_NAME}
 ```
 
 1. Submit the job. Run with `--help` for customization options.