在Shell中进行字符串大小比较

到网上摘抄了下面2个方法
====方法①===========
a="2004.03.08"
b="2005.03.08"
c=`expr $a \>= $b`
if [ $c -eq 1 ]
then
echo $a \>= $b
else
echo $a \< $b
fi




====方法②============
DATE="ef"

MODIFY="ab"

echo "`echo -e "$MODIFY \n$DATE"|sort| head -1 `"

if [ "$MODIFY" = `echo -e "$MODIFY \n$DATE"|sort| head -1 ` ]

then

echo "MODIFY is little than DATE"

else

echo "MODIFY is greater that DATE"

fi



====方法三========
如果是仅仅比较时间,可以把时间转换成整数比较,下面是示例

while [  `date -d $fromDay +%s` -le `date -d $toDay +%s ` ] 
do
        dim_date=$fromDay
        echo $dim_date
        fromDay=`date +%Y-%m-%d -d "$fromDay 1day"`
done

参考(里面有Bug,但是思路是正确的):
http://www.diybl.com/course/3_program/shell/shelljs/20110903/559590.html