sed和awk

sed：stream editor :一次处理一行内容，处理时，把当前的行存储在临时缓冲区，处理完后，输送到屏幕

sed [参数] '命令' file
	p	##显示
	d	##删除
	a	##添加
	c	##替换
	i	##插入

---

p静默状态下的显示：

 1. 
[root@localhost mnt]# cat /etc/fstab 
    
    #
    # /etc/fstab
    # Created by anaconda on Wed May  7 01:22:57 2014
    #
    # Accessible filesystems, by reference, are maintained under '/dev/disk'
    # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
    # UUID=9bf6b9f7-92ad-441b-848e-0257cbb883d1 /                       xfs     defaults        1 1 [root@localhost mnt]# cat -n /etc/fstab 
         1	
         2	#
         3	# /etc/fstab
         4	# Created by anaconda on Wed May  7 01:22:57 2014
         5	#
         6	# Accessible filesystems, by reference, are maintained under '/dev/disk'
         7	# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
         8	#
         9	UUID=9bf6b9f7-92ad-441b-848e-0257cbb883d1 /                       xfs     defaults        1 1
    
    
    [root@localhost mnt]# sed -n '/\:/p' /etc/fstab      显示含有：的行（：需要转译）
    # Created by anaconda on Wed May  7 01:22:57 2014 [root@localhost mnt]# sed -n '/-/p' /etc/fstab 
    UUID=9bf6b9f7-92ad-441b-848e-0257cbb883d1 /                      
    xfs     defaults        1 1
    
    
    
    [root@localhost mnt]# sed -n '/^#/p' /etc/fstab 显示以#开头的行
    #
    # /etc/fstab
    # Created by anaconda on Wed May  7 01:22:57 2014
    #
    # Accessible filesystems, by reference, are maintained under '/dev/disk'
    # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
    
    
    [root@localhost mnt]# sed -n '/^#/!p' /etc/fstab   显示不以#开头的行
    
    UUID=9bf6b9f7-92ad-441b-848e-0257cbb883d1 /                      
    xfs     defaults        1 1
    
    
    [root@localhost mnt]# sed -n '2,6p' /etc/fstab 显示2-6行
    #
    # /etc/fstab
    # Created by anaconda on Wed May  7 01:22:57 2014
    #
    # Accessible filesystems, by reference, are maintained under '/dev/disk'
    
    
    
    [root@localhost mnt]# sed -n '2,6!p' /etc/fstab 显示除过2-6行
    
    # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
    # UUID=9bf6b9f7-92ad-441b-848e-0257cbb883d1 /                       xfs     defaults        1 1

d删除模式

[root@localhost mnt]# sed '/^UUID/d' /etc/fstab    		 删除以UUID开头的行

#
# /etc/fstab
# Created by anaconda on Wed May  7 01:22:57 2014
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
[root@localhost mnt]# sed '/^#/d' /etc/fstab 		删除以#开头的行
[root@localhost mnt]# sed '/^$/d' /etc/fstab 		删除空格
[root@localhost mnt]# sed '1,4d' /etc/fstab 		删除1-4行
#

a：添加模式

[root@localhost mnt]# cat westos 
haha
[root@localhost mnt]# sed '/haha/ahello' westos 
haha
hello

c:替换

[root@localhost mnt]# sed '/haha/chello world' westos 
hello world

i：插入(不改变源文件内容)

[root@localhost mnt]# sed '/haha/iworld\nwestos' westos 
world
westos
haha

i （改变源文件内容）

[root@localhost mnt]# sed -i 's/haha/redhat/' westos 
[root@localhost mnt]# cat westos 
redhat
[root@localhost mnt]# sed -i 's/redhat/westos/g' westos 		全局替换
[root@localhost mnt]# cat westos 
westos
[root@localhost mnt]# 

2.awk报告生成器
1）awk处理机制：根据模式一次从文件中抽取一行文本，对这行文本进行切片（默认使用空白字符作为分隔符）

[root@server mnt]# cat test
this  | is | a | file
 $1     $2  $3    $4

awk '{print $0}' test	##$0表示输出一整行

awk '{print $1}' test

awk '{print $4}' test

awk '{print $1,$2}' test	##显示两个字段

awk -F ":" '{print $1,$3}' /etc/passwd	##指定分隔符

2）awk常用变量

awk '{print FILENAME,NR}' /etc/passwd	##输出文件名，和当前操作的行号

awk -F: '{print NR,NF}' /etc/passwd	##输出每次处理的行号，以及当前以":"为分隔符的字段个数

总结：awk '{print "第NR行"，"有NF列"}' /etc/passwd


BEGIN{}:读入第一行文本之前执行的语句，一般用来初始化操作
{}:逐行处理
END{}:处理完最后以行文本后执行，一般用来处理输出结果

awk 'BEGIN { a=34;print a+10 }'

awk -F: 'BEGIN{print "REDHAT"} {print NR;print } END {print "WESTOS"}' passwd 		##文件开头加REDHAT，末尾加WESTOS，打印行号和内容

awk -F: '/bash$/{print}' /etc/passwd	##输出以bash结尾的

awk -F: 'NR==3 {print}' /etc/passwd

awk -F: 'NR % 2 == 0 {print}' /etc/passwd	##偶数行

awk -F: 'NR >=3 && NR <=5 {print }' /etc/passwd

awk 'BEGIN{i=0}{i+=NF}END{print i}' linux.txt	##统计文本总字段个数