Regular expression exercise

1、 Show /proc/meminfo The size of the file s Beginning line （ requirement , Use two methods ）

2、 Show /etc/passwd Not in the document /bin/bash The line at the end

3、 Show users root default shell Program

4、 find /etc/passwd Two or three digits in

5、 Show /etc/grub2.cfg In file , A line that begins with at least one white space character and is followed by a non white space character

6、 find netstat -tan In the command result listen A line that ends with any number of white space characters

7、 Add users bash、tesbash、basher、sh、nologin（shell by /sbin/nologin）, find shell Row with the same name as the user

8、 utilize df and grep, Take out the utilization of each partition of the disk , And sort

9、 Show three users root、lgw、admin Of uid And default shell（ Extended regularization ）

10、 find /etc/rc.d/init.d/functions The first line in the file is a word （ Include underline ） The line followed by a parenthesis

11、 Use egrep Take out /etc/rc.d/init.d/functions Middle base name

11、 Use egrep Take out /etc/rc.d/init.d/functions Directory name in

12、 Statistics last In the order root Every host that logs in ip Address login times

13、 Use regular expressions to express 0-9、10-99、100-99、200-249、250-255;

14、 Show ifconfig All in the command result ipv4 Address

15、 Put this string welcome to lgw  company Each character in is de duplicated and sorted , The one with the most repetitions is at the top .