Bash script store command output into variable

Question

I have a problem concerning storing the output of a command inside a variable within a bash script.
I know in general there are two ways to do this

either

foo=$(bar)
# or
foo=`bar`

but for the Java version query, this doesn't seem to work.

I did:

version=$(java --version)

This doesn't store the value inside the var. It even still prints it, which really shouldn't be the case.

I also tried redirecting output to a file but this also fails.

user unknown · Answer 1 · 2012-03-19 10:09:38Z

up vote 8 down vote

 version=$(java -version 2>&1)

The version param only takes one dash, and if you redirect stderr, which is, where the message is written to, you'll get the desired result.

answered Mar 19 '12 at 10:09

user unknown
12.8k52051

thanks a ton, exactly what i was looking for – user1278282 Mar 19 '12 at 12:31

bmk · Answer 2 · 2012-03-19 10:21:19Z

up vote 4 down vote

That is because java -version writes to stderr and not stdout. You should use:

version=$(java -version 2>&1)

In order to redirect stderr to stdout.

You can see it by running the following 2 commands:

java -version > /dev/null

java -version 2> /dev/null

edited Mar 19 '12 at 10:21

bmk
5,0721820

answered Mar 19 '12 at 10:15

Eran Ben-Natan
54917

thank you for your insight, it seems top also prints the version too stderr – user1278282 Mar 19 '12 at 12:31

2 Answers