shelll脚本，常见的脚本题目。

[root@localhost wyb]# cat 2quan.sh 
#!/bin/bash

#写一个脚本，先要求输入用户名，然后让他输入一个数字，输的如果是数字给输出yes，不是数字，输出no
#然后如果输入三次以上不是数字锁定此用户，就是不能让他上了
#要求次数累加，即使关了脚本再重启，也没用，依旧锁定，次数到了3就锁定
read_user()
{

read -p "Please Input a Username:" username

}
read_user
while [ -z $username ]
do
    read_user
done

[ ! -f $username.log ] && touch $username.log


judge_user()
{
   key=`cat $username.log|wc -l`
   [ $key -ge 3 ] && echo "This $username is lock" && exit
}

judge_user
echo ‘input `quit`to quit‘
while :
do
  judge_user
  read -p "Pleas input a number:" num
   [ -z $num ] && continue
   [[ "$num" = "quit" ]] && break
   
   expr $num + 1 &>/dev/null
  [ $? -ne 0 ] && echo error  >> $username.log && echo no|| echo yes

done
[root@localhost wyb]# bash 2quan.sh 
Please Input a Username:cheng
input `quit`to quit
Pleas input a number:eee
no
Pleas input a number:123
yes
Pleas input a number:123
yes
Pleas input a number:ddd
no
Pleas input a number:aaa
no
This cheng is lock
[root@localhost wyb]# bash 2quan.sh 
Please Input a Username:cheng
This cheng is lock
[root@localhost wyb]# bash 2quan.sh 
Please Input a Username:jing
input `quit`to quit
Pleas input a number:123
yes
Pleas input a number:bbb
no
Pleas input a number:ddd
no
Pleas input a number:aaa
no
This jing is lock
[root@localhost wyb]# bash 2quan.sh 
Please Input a Username:quit
input `quit`to quit
Pleas input a number:quit
[root@localhost wyb]# cat jing.log 
error
error
error
[root@localhost wyb]# cat cheng.log 
error
error
error
[root@localhost wyb]#