shell文本处理3：sed

Sed 行编辑器

sed（stream editor）：

1. 用来操作纯 ASCII 码的文本
2. Sed 一次处理一行内容
   处理时，把当前处理的行存储在临时缓冲区中，称之为“模式空间”（pattern space）
3. 可以指定仅仅处理哪些行，Sed 符合模式条件的处理，不符合条件的不予处理
4. 处理完成之后把缓冲区的内容送往屏幕
5. 接着处理下一行,这样不断重复,直到文件末尾

sed命令格式

sed [参数] ‘命令’ file

Sed 对字符的处理

p 　　　##显示，将某个选择的数据打印显示。通常 p 会与参数 sed -n 一起执行
d 　　　##删除，显示模式空间删除指定行后的内容，不会对原文件数据删除
a 　　　##添加，a 的后面可以接字符串，该字符串会在当前指定行的下一行出现
c 　　　##更改， c 的后面可以接字符串，该字符串可以取代 n1,n2 之间的行
i 　　　##插入， i 的后面可以接字符串，该字符串会在当前指定行的上一行出现

p

[root@foundation63 mnt]# cat -n /etc/fstab 
     1	
     2	#
     3	# /etc/fstab
     4	# Created by anaconda on Sun Sep 23 22:41:24 2018
     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	/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
    10	UUID=9bbad413-0771-45fc-9ddb-fd2ba6994561 /boot                   xfs     defaults        0 0
    11	UUID=A5EB-573A          /boot/efi               vfat    umask=0077,shortname=winnt 0 0
    12	/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0
[root@foundation63 mnt]#  sed -n '/\:/p' /etc/fstab 
# Created by anaconda on Sun Sep 23 22:41:24 2018
[root@foundation63 mnt]# sed -n '/^#/p' /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Sep 23 22:41:24 2018
#
# 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@foundation63 mnt]# sed -n '/^#/!p' /etc/fstab

/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
UUID=9bbad413-0771-45fc-9ddb-fd2ba6994561 /boot                   xfs     defaults        0 0
UUID=A5EB-573A          /boot/efi               vfat    umask=0077,shortname=winnt 0 0
/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0
[root@foundation63 mnt]#  sed -n '2,6p' /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Sep 23 22:41:24 2018
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
[root@foundation63 mnt]# sed -n '2p;6p' /etc/fstab  
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'

d

[root@foundation63 mnt]# sed '/^UUID/d' fstab 

#
# /etc/fstab
# Created by anaconda on Sun Sep 23 22:41:24 2018
#
# 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
#
/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0
[root@foundation63 mnt]#  sed '/^#/d' fstab 

/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
UUID=9bbad413-0771-45fc-9ddb-fd2ba6994561 /boot                   xfs     defaults        0 0
UUID=A5EB-573A          /boot/efi               vfat    umask=0077,shortname=winnt 0 0
/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0
[root@foundation63 mnt]# sed '/^$/d' fstab 
#
# /etc/fstab
# Created by anaconda on Sun Sep 23 22:41:24 2018
#
# 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
#
/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
UUID=9bbad413-0771-45fc-9ddb-fd2ba6994561 /boot                   xfs     defaults        0 0
UUID=A5EB-573A          /boot/efi               vfat    umask=0077,shortname=winnt 0 0
/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0
[root@foundation63 mnt]#  sed '1,4d' fstab 
#
# 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
#
/dev/mapper/rhel_foundation63-root /                       xfs     defaults        0 0
UUID=9bbad413-0771-45fc-9ddb-fd2ba6994561 /boot                   xfs     defaults        0 0
UUID=A5EB-573A          /boot/efi               vfat    umask=0077,shortname=winnt 0 0
/dev/mapper/rhel_foundation63-swap swap                    swap    defaults        0 0

a

[root@foundation63 mnt]# cat hello.sh 
hello
[root@foundation63 mnt]# sed '/hello/aworld' hello.sh 
hello
world
[root@foundation63 mnt]# sed 's/hello/hello world/g' hello.sh 
hello world
[root@foundation63 mnt]# 
[root@foundation63 mnt]# sed 's/hello/hello\nworld/g' hello.sh
hello
world

c

[root@foundation63 mnt]# sed '/hello/chello world' hello.sh
hello world

i

[root@foundation63 mnt]# sed '/hello/iworld\nwestos' hello.sh 
world
westos
hello

练习：

将httpd服务的端口80改为8080

#!/bin/bash
yum install httpd -y $> /dev/null
sed -i "/^Listen/cListen $1" /dev/httpd/conf/httpd.conf
echo -e "Port has changed!"
echo "Now,port is $1!"
ststemctl restart httpd

~