shell字符串转换成数字

convert_string(){  
    str=$1  
    sum=0  
    index=0  
    length=${#str}  
      
    while [ ${index} -lt ${length} ]  
    do  
        let sum=10*sum+${str:${index}:1}  
        let index+=1  
    done  
      
    echo ${sum}  
}