"Invalid arithmetic operator" error when checking hostname in Bash script

Question

I have a simple hostname check in a bash script:

if [[ `hostname` -eq "cps1214" ]]
then
    JAVA_HOME=/usr/local/jdk1.6.0_21
fi

On our old SuSE 8 system this works fine. On our newer CentOS system this causes an error:

[[: dev.example.com: syntax error: invalid arithmetic operator
(error token is ".example.com")

I'm not really sure what the issue is here. My understanding is that -eq is explicitly for string comparisons, hostname is clearly returning a string, and the right-hand side is also a string. Why is it complaining about arithmetic?

I think you got Bash and Perl confused. Bash -eq is specifically for numeric comparison, not strings. — Mark Reed
– Mark Reed, Commented Nov 8, 2013 at 21:06

fregante · Accepted Answer · 2017-07-12 02:10:00Z

3

Because -eq is not for string comparisons, but an arithmetic operator, as described in the bash documentation.

You can swap -eq with = or ==, and you are fine.

edited Jul 12, 2017 at 2:10

fregante

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answered Nov 8, 2013 at 20:55

user2719058

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2 Comments

ficuscr Over a year ago

tldp.org/LDP/abs/html/comparison-ops.html Also beware white space and note the number of brackets effect on the comparison.

Brad Mace Over a year ago

the double-quotes used in examples I looked at led me to believe they were comparing as strings, but evidently double-quotes get sprayed everywhere in bash scripts. Changing to == has it working on both systems.

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