Check if Java Installed with Bash

Question

Can someone tell me why this simple command cannot find the output "java version"?

if java -version | grep -q "java version" ; then
  echo "Java installed."
else
  echo "Java NOT installed!"
fi

output from java -version is as follows

java version "1.8.0_77"
Java(TM) SE Runtime Environment (build 1.8.0_77-b03)
Java HotSpot(TM) 64-Bit Server VM (build 25.77-b03, mixed mode)

You're not actually checking the output or version, so is there a reason why you don't just use `which`? — dovetalk, Apr 03 '16 at 17:07
Why grep for the version, when you could just check if the binary itself exists and is executable? — OneCricketeer, Apr 03 '16 at 17:07
Binary is not in the same place on every machine, wouldn't be sound to test src. — WASasquatch, Apr 03 '16 at 17:23
Check this out: http://stackoverflow.com/questions/7334754/correct-way-to-check-java-version-from-bash-script — okutane, Feb 06 '17 at 15:34

Reimeus · Answer 1 · 2016-04-03T17:15:53.770

8

java outputs to STDERR. You can use

if java -version 2>&1 >/dev/null | grep -q "java version" ; then

but probably simpler to do something like

if [ -n `which java` ]; then

edited Apr 03 '16 at 17:15

answered Apr 03 '16 at 17:04

Reimeus

I noticed `which` is not always available from testing this software on multiple machines from the get go to see what is available. Why I was testing the java command. Thanks for the time. – WASasquatch Apr 03 '16 at 17:25

score 1 · Accepted Answer · answered Aug 28 '19 at 12:02

1

If your java is openJDK then you can use following options

java -version 2>&1 >/dev/null | grep "java version\|openjdk version"

or you can make more generic by

java -version 2>&1 >/dev/null | egrep "\S+\s+version"

to get java version

JAVA_VER=$(java -version 2>&1 >/dev/null | egrep "\S+\s+version" | awk '{print $3}' | tr -d '"')

answered Aug 28 '19 at 12:02

chitresh

egrep is nonstandard, probably better so do grep -E "\S+\s+version" – Prithvi Boinpally Jun 30 '21 at 21:12

2 Answers2