Bad substitution for string passed as argument

Question

I'm writing a script that, at one point, needs to compute the length of a string to draw a box around it. I can't use wc -c for that effect because I will use it for non-ASCII characters (sad). I'm also avoiding bashims for maximum compatibility.

I'm using the shell's built-in string length calculator:

string="string"
echo ${#string}
# 6
string="stríñg"
echo ${#string}
# 6

So far so good, but now when I pass it as an argument...

_function () {
  string_length=$(${#"$1"})
}
# line 21: ${#"$1"}: bad substitution

Priting $string_length doesn't show anything as well.

What am I doing terribly wrong?

Answer 1

It's

string_length=${#1}

The variable is 1 , so $1 or ${1} get's the value of the variable. Then ${#1} get's the length of 1 after expansion.