ffmpeg read file length (unit: second)

GetFileDuration(){
	fileUrl=$1
	duration_line=`./ffmpeg -i $fileUrl 2>&1 | grep 'Duration'`
	duration_1=${duration_line%%,*}
	duration_2=${duration_1%%.*}
	duration_3=${duration_2#*:}
	echo $duration_3
	durationList=(${duration_3//:/ })
	duration_senconds=0
	duration_senconds=$(($duration_senconds+${durationList[2]}))
	duration_senconds=$(($duration_senconds+${durationList[1]}*60))
	duration_senconds=$(($duration_senconds+${durationList[0]}*3600))
	duration=$duration_senconds
}

transfer:

let duration=0

GetFileDuration file name