sed运用实例一——基于变量的动态替换

在工作中我需要修改两个文件:

文件一:/etc/vmware/networking

1. VERSION=1,0
2. answer VNET_1_DHCP yes
3. answer VNET_1_DHCP_CFG_HASH 50CE8453B1072EA401BFFA704E6C01F7AE0BA67C
4. answer VNET_1_HOSTONLY_NETMASK 255.255.255.0
5. answer VNET_1_HOSTONLY_SUBNET 172.16.77.0
6. answer VNET_1_VIRTUAL_ADAPTER yes
7. answer VNET_8_DHCP yes
8. answer VNET_8_DHCP_CFG_HASH 1DA1A936DCB3AA3313CF293A9C96D25B76AB48A2
9. answer VNET_8_HOSTONLY_NETMASK 255.255.255.0
10. answer VNET_8_HOSTONLY_SUBNET 192.168.43.0
11. answer VNET_8_NAT yes
12. answer VNET_8_VIRTUAL_ADAPTER yes

文件二:/etc/vmware/vmnet8/dhcpd/dhcpd.conf

1. # Configuration file for ISC 2.0 vmnet-dhcpd operating on vmnet8.
2. #
3. # This file was automatically generated by the VMware configuration program.
4. # See Instructions below if you want to modify it.
5. #
6. # We set domain-name-servers to make some DHCP clients happy
7. # (dhclient as configured in SuSE, TurboLinux, etc.).
8. # We also supply a domain name to make pump (Red Hat 6.x) happy.
9. #
10. ###### VMNET DHCP Configuration. Start of "DO NOT MODIFY SECTION" #####
11. # Modification Instructions: This section of the configuration file contains
12. # information generated by the configuration program. Do not modify this
13. # section.
14. # You are free to modify everything else. Also, this section must start
15. # on a new line
16. # This file will get backed up with a different name in the same directory
17. # if this section is edited and you try to configure DHCP again.
18. # Written at: 03/22/2013 15:49:55
19. allow unknown-clients;
20. default-lease-time 1800; # default is 30 minutes
21. max-lease-time 7200; # default is 2 hours
22. subnet 192.168.43.0 netmask 255.255.255.0 {
23. range 192.168.43.128 192.168.43.254;
24. option broadcast-address 192.168.43.255;
25. option domain-name-servers 192.168.43.2;
26. option domain-name localdomain;
27. default-lease-time 1800; # default is 30 minutes
28. max-lease-time 7200; # default is 2 hours
29. option netbios-name-servers 192.168.43.2;
30. option routers 192.168.43.2;
31. }
32. host vmnet8 {
33. hardware ethernet 00:50:56:C0:00:08;
34. fixed-address 192.168.43.1;
35. option domain-name-servers 0.0.0.0;
36. option domain-name "";
37. option routers 0.0.0.0;
38. }
39. ####### VMNET DHCP Configuration. End of "DO NOT MODIFY SECTION" #######

需求:

将两个文件中的"192.168.43"修改为"202.16.22",不过,有时"192.168.43"会表现为其它的IP值,而要修改的目标字串"202.16.22"也可能会随着环境的改变另行设置.

基于此需求,本人编写了如下测试脚本:

针对文件一:

1. #!/bin/bash
2. # $vmnat_subnet_old变量表示vmnat8原有的子网配置,注意只截取前三段
3. vmnat_subnet_old=`grep "VNET_8_HOSTONLY_SUBNET" /etc/vmware/networking | sed 's/..$//' | cut -d' ' -f 3`
4. # $vmnat_subnet_new变量表示vmnat8子网的目标配置,注意只截取前三段
5. vmnat_subnet_new='192.168.40'
6. cp /etc/vmware/networking /etc/vmware/networking_bak0
7. sed -i '/VNET_8_HOSTONLY_SUBNET/s/'"$vmnat_subnet_old"'/'"$vmnat_subnet_new"'/' /etc/vmware/networking
8. grep "$vmnat_subnet_new" /etc/vmware/networking
9. cp /etc/vmware/networking_bak0 /etc/vmware/networking

针对文件二:

1. #!/bin/bash
2. # $vmnat_subnet_new变量表示vmnat8子网的目标配置,注意只截取前三段
3. vmnat_subnet_new='192.168.40'
4. # $vmnat_subnet_old变量表示vmnat8原有的子网配置,注意只截取前三段
5. vmnat_subnet_old=`grep "VNET_8_HOSTONLY_SUBNET" /etc/vmware/networking | sed 's/..$//' | cut -d' ' -f 3`
6. cat /etc/vmware/vmnet8/dhcpd/dhcpd.conf
7. cp /etc/vmware/vmnet8/dhcpd/dhcpd.conf /etc/vmware/vmnet8/dhcpd/dhcpd.conf_bak0
8. sed -i '/'"$vmnat_subnet_old"'/s//'"$vmnat_subnet_new"'/g' /etc/vmware/vmnet8/dhcpd/dhcpd.conf
9. grep "$vmnat_subnet_new" /etc/vmware/vmnet8/dhcpd/dhcpd.conf
10. cp /etc/vmware/vmnet8/dhcpd/dhcpd.conf_bak0 /etc/vmware/vmnet8/dhcpd/dhcpd.conf

优点：

可以不用事先知道要替换的字符是（本例中：192.168.43）什么，只需要知道自己想替换为（本例中：202.16.22）什么就可以了。

呵呵，我的工作桌面截图。