CODEWITHSUNDEEP
bashshellif-statement
Uranus
Uranus

Reputation: 71

error: line 9: * 12: syntax error: operand expected

I've been getting the error: line 9: * 12: syntax error: operand expected (error token is "* 12") (I entered 3, 4, 1 as a test on the script) the result that I need still shows at the end but after this error line. Why is that line showing if everything "works"?

Here's my code so you can understand what I did:

y='1'
z='0'

while [ $z = 0 ]
do
read x
        if [[ "$x" -ge "0" ]];
        then
        y=$[$x*$y]
        fi
done

echo -n "The multiplication of positive numbers entered is: $y"

exit

Upvotes: 0

Views: 1614

Answers (3)

janos
janos

Reputation: 124646

line 9: * 12: syntax error: operand expected (error token is "* 12")

How is this possible? The message is trying to tell you that an operand is expected, but it wasn't there. As an additional hint, the error token is * 12. Look closely where this might be.

This happens in the expression $x*$y. For example if x is 2, and y is 12, then the expression is 2 * 12. But if the value of x is the empty string, then the expression is * 12, that is, nothing multiplied by 12. That makes no sense, hence the error.

When x has no value (you entered a blank line), you probably want to break out of the loop:

while [ $z = 0 ]; do
    read x
    [[ $x ]] || break
    if [[ "$x" -ge "0" ]]; then
        y=$[$x*$y]
    fi
done

In addition, as @mklement0 pointed out in a comment, the $[...] syntax is obsoleted in favor of $((...)), and there's no good reason to mix [...] and [[...]] style conditionals. Here's a more modern, cleaner version of your script, also with the unused z variable eliminated:

while true; do
    read x
    [[ $x ]] || break
    if ((x >= 0)); then
        ((y = x * y))
    fi
done

Upvotes: 2

choroba
choroba

Reputation: 241838

How do you end the input? If you entered Ctrl + d or an empty string, x was emtpy, and the shell tried to assign

y=$[*12]

Hence the error. I don't see why the loop ends in such a case, though, as $z never changes.

Upvotes: 2

Tom Fenech
Tom Fenech

Reputation: 74605

The syntax of this line isn't correct:

y=$[$x*$y]

To assign the result of $x * $y to $y, use this:

y=$(( x * y ))

Remember that the shell only supports integer arithmetic.

Upvotes: 0

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