shell脚本截取日期处理

[Author]: kwu 

shell脚本截取日期处理，在linux中日期格式化固定为8位：2015-01-01

如实现 2015-1-1 需要进行字符串处理

 #!/bin/sh
 # upload logs to hdfs


 yesterday2="2015-01-08"

 echo ${yesterday2}

 first=${yesterday2:5:1}
 second=${yesterday2:8:1}

 echo ${first}
 echo ${second}

 res=$yesterday2
 echo ${res}

 if [ $first -eq 0 ] && [ $second -eq 0 ]
 then
     res=${yesterday2:0:5}${yesterday2:6}
     res=${res:0:7}${res:8}
 elif [ $first -eq 0 ]
 then
     res=${yesterday2:0:5}${yesterday2:6}
 elif [ $second -eq 0 ]
 then
     res=${yesterday2:0:8}${yesterday2:9}
 fi

 echo ${res}

如上命令最终输出为

2015-1-8