Task

Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.

Note: The order of the middle digits should be preserved.

Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:

123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345
1, 2, -1, -10, 2002, -2002, 0

Show your output on this page.




function middle3digits 
{ 
  typeset -i n="${1#-}"
  typeset -i l=${#n}
  if (( l < 3 )); then
    echo >&2 "$1 has less than 3 digits"
    return 1
  elif (( l % 2 == 0 )); then
    echo >&2 "$1 has an even number of digits"
    return 1
  else
    echo ${n:$((l/2-1)):3}
    return 0
  fi
}
 
# test
testdata=(123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1
          -10 2002 -2002 0)
for n in ${testdata[@]}; do
  printf "%10d: " $n
  middle3digits "$n"
done