printf field width doesn't support multibyte characters?

Question

I want printf to recognize multi-byte characters when calculating the field width so that columns line up properly... I can\'t find an answer to this problem and was wonderi

Answer 1

The best I can think of is:

function formatwidth
{
  local STR=$1; shift
  local WIDTH=$1; shift
  local BYTEWIDTH=$( echo -n "$STR" | wc -c )
  local CHARWIDTH=$( echo -n "$STR" | wc -m )
  echo $(( $WIDTH + $BYTEWIDTH - $CHARWIDTH ))
}

printf "## %5s %*s %5s ##\n## %5s %*s %5s ##\n" \
    '' $( formatwidth "*" 5 ) '*' '' \
    '' $( formatwidth "•" 5 ) "•" ''

You use the * width specifier to take the width as an argument, and calculate the width you need by adding the number of additional bytes in multibyte characters.

Note that in GNU wc, -c returns bytes, and -m returns (possibly multibyte) characters.