Java major version check in bash script

Question

I've just installed Kafka following tutorial. It doesn't start because of sh script error:

$ sudo kafka-server-start.sh /etc/kafka.properties /opt/Kafka/kafka_2.12-1.1.0/bin/kafka-run-class.sh: line 252: [[: 10 2018-04-17: syntax error in expression (error token is "2018-04-17") [0.000s][warning][gc] -Xloggc is deprecated. Will use -Xlog:gc:/opt/Kafka/kafka_2.12-1.1.0/bin/../logs/kafkaServer-gc.log instead. Unrecognized VM option 'PrintGCDateStamps' Error: Could not create the Java Virtual Machine. Error: A fatal exception has occurred. Program will exit. 

checking line 252:

if [[ "$JAVA_MAJOR_VERSION" -ge "9" ]] ; then 

I've added echo to get more info:

JAVA_MAJOR_VERSION=$($JAVA -version 2>&1 | sed -E -n 's/.* version "([^.-]*).*"/\1/p') echo "JAVA_MAJOR_VERSION: $JAVA_MAJOR_VERSION" if [[ "$JAVA_MAJOR_VERSION" -ge "9" ]] ; then 

output is changed with:

JAVA_MAJOR_VERSION: 10 2018-04-17

my java:

$ java -version openjdk version "10.0.1" 2018-04-17 

Question

How I should change JAVA_MAJOR_VERSION=$($JAVA -version 2>&1 | sed -E -n 's/.* version "([^.-]*).*"/\1/p') to fix my Kafka starter?

Answer 1

This works for older "1.x.y" format as well as newer "x.y" format:

java -version 2>&1 \ | head -1 \ | cut -d'"' -f2 \ | sed 's/^1\.//' \ | cut -d'.' -f1 

Source: https://odoepner.wordpress.com/2014/07/27/get-java-version-string-via-shell-commands/

Answer 2

One solution is to drop the date off the end by using cut. This approach would result in:

JAVA_MAJOR_VERSION=$($JAVA -version 2>&1 | sed -E -n 's/.* version "([^.-]*).*"/\1/p' | cut -d' ' -f1) 

This approach splits on the space character (-d' ') and takes the first field. Based upon the input, that would drop the openjdk appended date.