Question

I want to run the command mvn clean in a bash script. But I want to put it in an if statement. If the clean does not run properly I would like to exit out of the bash script with an echo statement.
Here is the code that is causing the problem:
if [ mvn clean ]; then

I tried putting $(mvn clean) inside the if statement but there were too many arguments says the terminal. Does anyone know if this is possible? Thanks!

Answer 1

Here’s what you want:

mvn clean
if [ "$?" -ne 0 ]; then
    echo "Maven Clean Unsuccessful!"
    exit 1
fi

Explanation:

• $? is a special shell variable that contains the exit code (whether it terminated successfully, or not) of the most immediate recently executed command.
• -ne is an option to the test builtin [. It stands for “not equal”. So here we are testing if the exit code from mvn clean is not equal to zero.
• echo "Maven Clean Unsucccessful!" – If this is the case, then we output some indicative message, and exit the script itself with an errant exit code.

When you do $(mvn clean), that instead spawns a new subshell to run mvn clean, then simply dumps everything that was output to stdout in that subshell from running mvn clean to where $(...) was used in the parent shell.

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Alternatively, you can do:

mvn clean || { echo "Maven Clean Unsuccessful"; exit 1; }

Which is just shorthand syntactic sugar for doing the same thing.