3. chpasswd - update passwords in batch mode
echo "user:password" | chpasswd
[root@dev1 ~]# adduser test
[root@dev1 ~]# echo "test:123456" | chpasswd
# cat passwd.txt
neo:neopass
jam:jampass
# cat passwd.txt | chpasswd
# chpasswd -c < passwd.txt
passwd 命令實現相同功能
echo "mypasword" | passwd –stdin neo