安装 watch
sudo brew install watch
iTerm or Terminal（终端）
示例代码
watch -t -n1 "date"
2016 3 29 20 33 54 CST
watch && figlet
watch -t -n1 "date +%T|figlet -f banner"
##### ### # ##### # # # #####
# # # # ### # # # # ### # # # #
# # # # # # # # # # # #
##### # # ##### # # # # ######
# # # # # ####### # ####### #
# # # ### # # # ### # # #
####### ### # ##### # # # #####
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