shell script array length

Question

I assume arguments to my shell scripts willbe ./x.sh subject N file1 file2 fileN So I am splicing argv from 3 till end candidates=${@:3}

now I want to check whether length of candidates is same as given N I am trying with echo $((${#candidates[@]})) which is always returning 1.

I can do echo "$#-2" | bc but, I shouldn't I be able to get array size ?

I can use bc to do integer comparison. but I've to know the size of `candidates array which I am not getting properly.

Yes, but what shell? ${@:3} is a syntax error in many shells. — William Pursell
– William Pursell, Commented Dec 14, 2012 at 16:51

William Pursell · Accepted Answer · 2012-12-14 17:19:30Z

2

The way you are assigning candidates is not making an array. To make it an array, do:

candidates=(${@:3})

In bash, you can get the number of elements in the array with ${#candidates[*]}. To check if that is equal to $2, just do:

[[ ${#candidates[*]} == "$2" ]]

answered Dec 14, 2012 at 17:01

William Pursell

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6 Comments

candidates=${@:3} echo ${#candidates[*]} is returning 1

candidates is not an array!

Thanks the parenthesis fixed it. one more question here I am slicing 3 to end. but how can I slice 3 to end-1 th element ?

You could do: candidates=(${@:3:$(($#-3))})

candidates=(${@:3:n}) always gets first element only doesn't matter whatever I put in place of n

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