正则表达式练习题

实例1-1 取出网卡的ip 地址

方法1

[[email?protected] /oldboy]# ip a s eth0 |awk 'NR==3'|awk? -F"[ /]+"? '{print $3}'

10.0.0.200

?[[email?protected] ~]# ifconfig eth0 |awk 'NR==2{}'

[[email?protected] ~]# ifconfig eth0 |awk 'NR==2{print $2}'

addr:10.0.0.200

方法2

[[email?protected] ~]# ifconfig eth0 |awk -F'[: ]+' 'NR==2{print $4}'

10.0.0.200

[[email?protected] ~]# ifconfig eth0

eth0????? Link encap:Ethernet? HWaddr 00:0C:29:59:D4:13?

????????? inet addr:10.0.0.200? Bcast:10.0.0.255? Mask:255.255.255.0

????????? inet6 addr: fe80::20c:29ff:fe59:d413/64 Scope:Link

????????? UP BROADCAST RUNNING MULTICAST? MTU:1500? Metric:1

????????? RX packets:52080 errors:0 dropped:0 overruns:0 frame:0

????????? TX packets:25292 errors:0 dropped:0 overruns:0 carrier:0

????????? collisions:0 txqueuelen:1000

????????? RX bytes:61200096 (58.3 MiB)? TX bytes:11691848 (11.1 MiB)

方法3

1>定位

[[email?protected] ~]# ip a s eth0 |sed -n 3p

2>把ip地址之前的内容替换掉

[[email?protected] ~]# ip a s eth0 |sed -n 3p |sed 's#^.*t ##g'

10.0.0.200/24 brd 10.0.0.255 scope global eth0

3>把ip地址之后的替换掉

[[email?protected] ~]# ip a s eth0 |sed -n 3p |sed 's#^.*t ##g'|sed 's#/.*$##g'

10.0.0.200

命令优化

使用2个sed

[[email?protected] ~]# ip a s eth0 |sed -n 3p |sed -r 's#^.*t |/.*$##g'

10.0.0.200

方法4 sed 后向引用

在前面先保护(你想要的内容),在后面通过数字使用

[[email?protected] ~]# ip a s eth0 |sed -n 3p

??? inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0

[[email?protected] ~]# ip a s eth0 |sed -n 3p |sed -r 's#^.*t (.*)/.*$#1#g'

10.0.0.200

实例1-2 ip a s eth0第三行的inet替换为oldboy

[[email?protected] ~]# ip a s eth0 |sed -n 3p

??? inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0

[[email?protected] ~]# ip a s eth0 |sed -n 3p|sed 's#inet#oldboy#g'

??? oldboy 10.0.0.200/24 brd 10.0.0.255 scope global eth0

实例1-3 只通过正则表达式取出ip

[[email?protected] ~]# ip a s eth0 |egrep '[0-9]{1,3}.[0-9]{1,3}'

??? inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0

[[email?protected] ~]# ip a s eth0 |egrep '([0-9]{1,3}.){3}[0-9]{1,3}'

??? inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0

[[email?protected] ~]# ip a s eth0 |egrep '([0-9]{1,3}.?){4}'

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

??? inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0

所有网卡的ip地址

[[email?protected] ~]# hostname -I

10.0.0.200

实例1-4 取出stat /etc/hosts 文件权限 644 或 0644?

方法1

awk

[[email?protected] ~]# stat /etc/hosts |awk 'NR==4'

Access: (0644/-rw-r--r--)? Uid: (??? 0/??? root)?? Gid: (??? 0/??? root)

[[email?protected] ~]# stat /etc/hosts |awk 'NR==4'|awk -F'[(/]'?? '{print $2}'

0644

[[email?protected] ~]# stat /etc/hosts |awk -F'[(/]'?? 'NR==4{print $2}'

0644

方法2

sed 后向引用

[[email?protected] ~]# stat /etc/hosts |sed -n 4p |sed -r 's#(^.*()([0-9]+)(/.*$)#1#g'

Access: (

[[email?protected] ~]# stat /etc/hosts |sed -n 4p |sed -r 's#(^.*()([0-9]+)(/.*$)#2#g'

0644

[[email?protected] ~]# stat /etc/hosts |sed -n 4p |sed -r 's#^.*(([0-9]+)/.*$#1#g'

0644

[[email?protected] ~]#

方法3

[[email?protected] ~]# stat -c%a? /etc/hosts

644

实例1-5 已知/oldboy/test.txt文件内容为：

oldboy

?

xizi

?

xiaochao

请问如何把文件中的空行过滤掉（要求命令行实现）。

通过三剑客进行过滤

方法1grep

[[email?protected] /oldboy]# grep -v '^$' test.txt

oldboy

xizi

xiaochao

方法2sed

[[email?protected] /oldboy]# sed '/^$/d' test.txt

oldboy

xizi

xiaochao

方法3awk

[[email?protected] /oldboy]# awk '!/^$/' test.txt

oldboy

xizi

xiaochao

实例1-6?????????? 已知/oldboy/ett.txt文件内容为：

oldboy

olldboooy

test

请使用grep或egrep正则匹配的方式过滤出前两行内容

方法1 egrep

[[email?protected] /oldboy]# egrep 'ol+dbo+y' ett.txt

oldboy

olldboooy

方法2sed

[[email?protected] /oldboy]# sed -nr '/ol+dbo+y/p'? ett.txt

oldboy

olldboooy

方法3awk

[[email?protected] /oldboy]# awk '/ol+dbo+y/' ett.txt

oldboy

olldboooy

实例1-7?????????? linux下通过mkdir命令创建新目录/oldboy/ett，ett的硬链接数是多少，为什么？

[[email?protected] /oldboy]# mkdir -p /oldboy/ett

[[email?protected] /oldboy]# ll -d ett

drwxr-xr-x 2 root root 4096 Jul 20 02:01 ett

[[email?protected] /oldboy]# ll -di ett ett/.

1046554 drwxr-xr-x 2 root root 4096 Jul 20 02:01 ett

1046554 drwxr-xr-x 2 root root 4096 Jul 20 02:01 ett/.

mkdir -p /oldboy/ett/oldboy

ett目录的硬连接数是？

[[email?protected] /oldboy]# ll -d ett

drwxr-xr-x 3 root root 4096 Jul 20 02:05 ett

[[email?protected] /oldboy]# ll -di ett ett/. ett/oldboy/..

1046554 drwxr-xr-x 3 root root 4096 Jul 20 02:05 ett

1046554 drwxr-xr-x 3 root root 4096 Jul 20 02:05 ett/.

1046554 drwxr-xr-x 3 root root 4096 Jul 20 02:05 ett/oldboy/..

实例1-8 按照要求的格式显示日期

[[email?protected] /oldboy]# date +%F

2018-07-20

[[email?protected] /oldboy]# date +%Y-%m-%d

2018-07-20

[[email?protected] /oldboy]# date +%T

02:29:22

[[email?protected] /oldboy]# date +%H:%M:%S

02:29:46

[[email?protected] /oldboy]# date +%w

5

小结：

%F? %Y-%m-%d??? 年-月-日

%T? %H:%M:%S??? 时:分:秒

%w????????????? 周几

实例1-9 显示当前日期格式: 年月日_小时

[[email?protected] /oldboy]# date +%F

2018-07-20

[[email?protected] /oldboy]# date -d "1 day ago"

Thu Jul 19 02:41:01 CST 2018

[[email?protected] /oldboy]# date -d "1day"

Sat Jul 21 02:41:15 CST 2018

[[email?protected] /oldboy]# date -d "-1day"

Thu Jul 19 02:41:28 CST 2018

[[email?protected] /oldboy]# date -d "-1day" +%F

2018-07-19

date 显示系统时间

-d? 根据你的描述显示指定日期

-d? '-7day'? 7天之前

-d? '7day'? 7天之后

-d '+7day'? 7天之后