思路：date -d " - 12hours" +%H判断时间
#!/bin/bash
d=`date +%H`
if [ $d -ge 0 -a $d -lt 7 ];then
tag=1
elif [ $d -ge 7 -a $d -lt 12 ];then
tag=2
elif [ $d -ge 12 -a $d -lt 18 ];then
tag=3
else
tag=4
fi
case $tag in
1)
echo "early in the morning !"
;;
2)
echo "Good morning !"
;;
3)
echo "Good afternoon !"
;;
4)
echo "Good evening !"
;;
*)
echo "Script error !"
;;
esac原文：https://blog.51cto.com/11594671/2555396