day19-三剑客之awk.png

补充—sed的后向引用

https://www.processon.com/view/link/5cb92f24e4b0bab9095ea765
筛选出stat /etc/hosts下的644

[✡root@oldboy /tmp]# stat /etc/hosts 
  File: ‘/etc/hosts’
  Size: 158         Blocks: 8          IO Block: 4096   regular file
Device: 803h/2051d  Inode: 16824726    Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-05-01 19:00:20.427999722 +0800
Modify: 2013-06-07 22:31:32.000000000 +0800
Change: 2019-03-26 13:52:54.724535531 +0800
 Birth: -
[✡root@oldboy /tmp]# stat /etc/hosts |sed -nr '4p'
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
[✡root@oldboy /tmp]# stat /etc/hosts|sed -n 4p|sed -r 's#(^.*\(0)([0-9]+)(/.*$)#\2#g'
\\此行命令就是用了后向引用
644

※三剑客之awk

下图是awk的执行过程 ima ge.png

1.取行------>NR==

取第一行    
[?root@oldboy /tmp]# awk 'NR==1' lidao.txt 
1 2 3 4 5 6 7 8 9 10

取带有oldboy的行
[✡root@oldboy /tmp]# awk '/oldboy/' lidao.txt 
I am oldboy teacher!
my blog is http://oldboy.blog.51cto.com
our size is http://blog.oldboyedu.com
oldboy oldboy oldboy

2.取列------->2第二列

image.png

取lidao.txt中的第一列和第三列内容   
[✡root@oldboy /tmp]# awk '{print $1,$3}' lidao.txt 
I oldboy
I linux.
 
I badminton
my is
our is
my is
 
not 
my am
oldboy oldboy

给分隔的字符添加内容
用双引号""
[✡root@oldboy /tmp]# awk '{print $1"@@##"$3}' lidao.txt 
I@@##oldboy
I@@##linux.
@@##
I@@##badminton
my@@##is{}
our@@##is
my@@##is
@@##
not@@##
my@@##am
oldboy@@##oldboy

显示oldboy.txt的第4行的第1列 第2列和第4列 
[✡root@oldboy /tmp]# cat lidao.txt|awk 'NR==4'
I like badminton ball,billiard ball and chinese chess!
[✡root@oldboy /tmp]# cat lidao.txt|awk 'NR==4 {print $1,$2,$4}' 
I like ball,billiard

找到这行的第一个字符 (以,逗号算一个分隔符)
[✡root@oldboy /tmp]# cat 2.txt 
I am lidao,my qq is 918391635
[✡root@oldboy /tmp]# awk -F"," '{print $1}' 2.txt 
I am lidao

找到这行的lidao和qq号码
[?root@oldboy /tmp]# cat 2.txt 
I am lidao,my qq is 918391635
[?root@oldboy /tmp]# awk -F "[, ]" '{print $3,$7}' 2.txt 
lidao 918391635

查看10.0.0.201是第几列(有空格和/)
[14:25 root@oldboy /tmp]# cat 1.txt 
  ////    10.0.0.201  /24   
I am oldboy teacher!
I teach linux.
I like badminton ball,billiard ball and chinese chess!
my blog is http://oldboy.blog.51cto.com
our size is http://blog.oldboyedu.com
my qq is 1351441522
[14:25 root@oldboy /tmp]# cat 1.txt |awk -F'[/ ]+' 'NR==1{print $2}'
10.0.0.201

3.比较 > _ >= _ < _ <= _ == _ !=

找出/etc/passwd下第三列大于999的行
[✡root@oldboy /tmp]# awk -F":" '$3>999' /etc/passwd
oldboy:x:1000:1000::/home/oldboy:/bin/bash
gyj:x:1001:1010::/home/gyj:/bin/bash

显示/etc/passwd中第4列大于0 并且 第4列小于1000的行
[✡root@oldboy /tmp]# awk -F":" '$4>0 && $4<1000' /etc/passwd
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
....省略

显示使用内存情况内存
[?root@oldboy /tmp]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  2.3G   17G  12% /
devtmpfs        980M     0  980M   0% /dev
tmpfs           991M     0  991M   0% /dev/shm
tmpfs           991M  9.6M  981M   1% /run
tmpfs           991M     0  991M   0% /sys/fs/cgroup
/dev/sda1       197M  133M   64M  68% /boot
tmpfs           199M     0  199M   0% /run/user/0

使用率大于百分之1的
[?root@oldboy /tmp]# df -h |awk '$5>1'
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  2.3G   17G  12% /
tmpfs           991M  9.6M  981M   1% /run
/dev/sda1       197M  133M   64M  68% /boot

使用率大于百分之10的
[?root@oldboy /tmp]# df -h |awk '$5+0>10'
/dev/sda3        19G  2.3G   17G  12% /
/dev/sda1       197M  133M   64M  68% /boot
[?root@oldboy /tmp]# 

三剑客练习题---https://www.jianshu.com/p/952188a96a3e