CODEWITHSUNDEEP
bashshell
Kintarō
Kintarō

Reputation: 3187

Why does shell script execute "then" block if the condition is 0?

I am new to shell script and I am seeing something that I don't understand.

Consider the code below:

function test {
    return 0
}

if test; then
   echo "hihi"
fi

If I execute the code, it will call "hihi". If the test return 1, it will not call.

I am just wondering why?

Upvotes: 1

Views: 53

Answers (2)

mtk
mtk

Reputation: 13709

Having a non-zero return value indicates some issue/error in Unix terminology, so if you replace the return 0 with some non-zero number you'll go into the else block

function test {
    return 1    # or any non-zero value
}

if test; then
   echo "hihi"
else
    echo 'else block'
fi

Output: 

else block

Upvotes: 1

user3899165
user3899165

Reputation:

In UNIX, an exit code of 0 is used to signal success, while a non-zero exit code signals some sort of error. You would read it as:

if operation_that_might_fail_succeeds; then
    echo "everything went ok!"
fi

Upvotes: 3

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