shell整数计算器

#! /bin/bash

checkInt() {
  arr=$1
  for i in "${arr[@]}" ; do
    temp=`echo $i | sed 's/[0-9]//g' | sed 's/[ ]*//g'`
    if [ -n "$temp" ]; then
      echo "$i must be integer"
      return 1
    fi
  done
  return 0
}

fuhao="" #判断符号
getFuhao() {
  f=$(echo $1 | grep +)
  if [ -n "$f" ]; then
    fuhao="+"
  fi
  f=$(echo $1 | grep -)
  if [ -n "$f" ]; then
    fuhao="-"
  fi
  f=$(echo $1 | grep x)
  if [ -n "$f" ]; then
    fuhao="x"
  fi
  f=$(echo $1 | grep /)
  if [ -n "$f" ]; then
    fuhao="/"
  fi
  #echo "fuhao=$fuhao"
}

getLast() {
  arr=$1
  last=0;
  case $fuhao in
  "+")
    last=$((${arr[0]} + ${arr[1]}))
    ;;
  "-")
    last=$((${arr[0]} - ${arr[1]}))
    ;;
  "x")
    last=$((${arr[0]} * ${arr[1]}))
    ;;
  "/")
    last=$((${arr[0]} / ${arr[1]}))
    ;;
  esac
  echo "${arr[0]} $fuhao ${arr[1]} = $last"
}

r="" #输入
checkinputAndCompute() {
  while true; do
      echo "please input two num to plus, eg: a +-x/ b"
      read r
      if [ -z "$r" ]; then
        echo "cannot be null"
      else
        r=`echo "$r" | sed 's/\\*/x/'`
        getFuhao $r
        arr=(${r//$fuhao/ })
        if [ ${#arr[@]} -ne 2 ]; then
          echo "error input, eg: a +-x/ b"
        else
          if checkInt $arr; then
            getLast $arr
          fi
        fi
      fi
  done
}

checkinputAndCompute