[code]for i in {1..4}dox=$[RANDOM%53]y=$[RANDOM%10]code1=${a:x:1}code2=${b:y:1}code=$code1$code2$codedoneecho $codeecho \'$code\' | mail -s \"code\" -r root rooti=1while [ $i -le 3 ]doread -p \"请输入正确的验证码:\" cif [ \"$c\" != \"$code\" ] || [ \"-z\" \"$c\" ];thenecho \"验证码错误\"let i++continueelseread -p \"验证码正确!,请输入要创建的用户名\" nuseradd $n &>/dev/nullusermod -s /bin/bash $n &>/dev/nullread -p \"请为用户名创建密码\" pecho \"$p\" | passwd --stdin $nif [ $? -ne 0 ];thenusermod -s /sbin/nologin $nread -p \"因为你没有输入密码,不能登录了,请重新输入要创建的用户名:\" m[ $m == $n ] && echo \"用户已经存在\"&&i=1&&continue[ $m != $n ] && i=1&&continuefifi