Use shell to calculate the sum of numbers in text

    A strange thing happened today ： use wc -l *.txt > wc.out In the file of , The last line is not the sum of the records of all the files counted . In this case , I still need to write a shell Script , Let's add up wc.out The sum of the numbers of each record in the document .
    The following is the corresponding script ,shell The parameter of is file name , Here is wc.out.wc.out The file format is 『 Numbers file name 』.
    The main idea is ： Read every line in the file , And then use cut command , Get the number in each line , Then add up this number .

#!/bin/bash

if [ $# -ne 1 ]
then
    echo "need one parameter: file_name needed"
    exit
fi

sum=0;
while read line; do amount=`echo $line|cut -d " " -f1`; sum=$(( ${amount} + $sum )) ;  done < $1;
echo "total amount is $sum"