隨機生成一個數字md5加密並且截圖字符串

root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# a=echo $RANDOM |md5sum |awk '{print $1}'
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo $a
0e662f747e4523855fe132a6a4903d12
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker#
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo $a
0e662f747e4523855fe132a6a4903d12
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:3:4}
62f7
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0:4}
0e66
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0:6}
0e662f
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0:6} >passwd1.txt
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# cat passwd1.txt
0e662f
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0:6}
0e662f
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a: -8}
a4903d12
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a: -5}
03d12
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0 -5}
03d12
root@iZuf6a50pk1lwwqhsq7cp2Z:/data/server/docker# echo ${a:0-5}