shell的这个脚本每一段具体的意思求大神解释！！！

VAR=254096
export KEY_NO=
BINSUFFIX=".bin"
CI_KEY="CI_KEY_"
export BINFILENAME=
export BINFILENAME2=

ls ./oldkey/ -1 >keylist.txt

sed -i "s/.bin//g" keylist.txt
for KEY_NO in $(cat keylist.txt)
do
BINFILENAME=${KEY_NO}${BINSUFFIX}
BINFILENAME2=${CI_KEY}${VAR}${BINSUFFIX}
cp ./oldkey/$BINFILENAME ./newkey/
mv ./newkey/$BINFILENAME ./newkey/$BINFILENAME2
VAR=$[VAR+1]
done