Trying to test variable for unset, and specific value for launching Docker entrypoint Java app in debug mode

Question

I am trying to follow the advice on How to check if a variable is set in Bash?

So our app is being deployed on AWS ECS cluster using CloudFormation Template, and sometimes we may need to switch on debug mode.

It seems the best way is to introduce an env variable DEBUG_MODE, that when is set to TRUE, the entrypoint.sh script would launch the java app with debug parameters.

Here is my latest attempt, I initially wanted to use && for single IF, but was getting error so trying to isolate it and split it in two:

if [ -z ${DEBUG_MODE+FALSE} ]
then
        echo not debug, not set
else
        if [ $DEBUG_MODE = TRUE ]
        then
                echo debug
        else
                echo not debug, set to $DEBUG_MODE
        fi
fi

Output:

user@hostname:~$ export DEBUG_MODE=
user@hostname:~$ sh test.sh
test.sh: 5: [: =: unexpected operator
not debug, set to

I cant seem to figure this out, how to write it so that:

If DEBUG_MODE is unset, empty, or anything but TRUE, it executes regular java command.
Only if DEBUG_MODE is TRUE, it executes java command with debug parameters?

Thanks!

Sergio Guillen Mantilla · Accepted Answer · 2019-10-17T15:33:37.403

0

you could simplify a bit that script without the need to check first if it's empty:

#!/bin/bash

if [[ "${DEBUG_MODE}" == 'TRUE' ]]; then
   # Run in debug mode
else
   # Run as usual
fi

Also I noticed you are using sh this solutions applies to bash, but isn't your Docker image already has bash installed?

In case you need sh only, problem seems to be in the comparison, you might need to wrap your variables with double quotes if [ "$DEBUG_MODE" = TRUE ]

if [ -z "${DEBUG_MODE+FALSE}" ]
then
        echo not debug, not set
else
        if [ "$DEBUG_MODE" = TRUE ]
        then
                echo debug
        else
                echo not debug, set to $DEBUG_MODE
        fi
fi

edited Oct 17 '19 at 15:33

answered Oct 17 '19 at 14:37

Sergio Guillen Mantilla

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Why does that solution I linked to, then checks first? – Carmageddon Oct 17 '19 at 15:01
In any case, dont you mean the reverse, meaning = instead of `!=`? – Carmageddon Oct 17 '19 at 15:01
I proposed this solution because if DEBUG_MODE is unset it will be evaluated as empty so no need to check if its set or not, just compare to the expected value to be TRUE to run in a special mode – Sergio Guillen Mantilla Oct 17 '19 at 15:07
image is alpine based, does not have bash available unfortunately :( – Carmageddon Oct 17 '19 at 15:11
And so using it in sh shell, with empty value for the var, causes error: `test.sh: 3: [: ==: unexpected operator start normal` (newline prints echo start normal from the else section) – Carmageddon Oct 17 '19 at 15:13
I tried variations of the syntax for sh, still getting similar errors for line 3.. like `[: unexpected operator` – Carmageddon Oct 17 '19 at 15:30
I edited, for sh only you will need to wrap variables with quotes – Sergio Guillen Mantilla Oct 17 '19 at 15:34
cool, I mentioned that in the last part of my answer but seems it was not very clear, sorry for that. Good it's working – Sergio Guillen Mantilla Oct 17 '19 at 15:38

Trying to test variable for unset, and specific value for launching Docker entrypoint Java app in debug mode

1 Answers1