download the easy fm more to learn mp3 from start day to now

mtw_download.sh

#!/bin/bash
#usage:
#download the easy fm more to learn mp3 from start day to now
trap ctrl_c INT
function ctrl_c(){
    echo "\n catched interput signal, exiting..."
    [ ! -e $current_process_file ] || rm $current_process_file
    echo "bye!"
    exit
}

start_time="20150101"
now=`date +%Y%m%d`
end_time=$now
#end_time="20131231"

it=$start_time
current_process_file=${it}".mp3"
while [ "$it" -le "$end_time" ]
do
    src_url="http://mod.cri.cn/eng/ez/mtl/${it:0:4}/atw${it:2:6}.mp3"
    echo "processing ${it:0:4}/${it:4:2}/${it:6:2}"
    echo "Downloading from $src_url ..."
    current_process_file=${it}".mp3"
    res=$( curl -s -o $current_process_file -w '%{http_code}\n' $src_url ) 
    if ((res != 200));then
        echo "http return: $res"
        rm ${it}".mp3"
    else
        echo "${it}.mp3 downloaded success."
    fi
    it=$(date -d "$it + 1 day" +%Y%m%d)
done

Thank you pengyou!