在bash中使用sed修改配置文件

I am trying to set net.ipv4.ip_forward to 1 in /etc/sysctl.conf.The following works fine but it sure missing some edge cases

我正在尝试设置net.ipv4。ip_forward to 1 in /etc/sysctl.conf。下面的操作很好，但是它确实遗漏了一些边缘情况

#Enable IP packet forwarding so that our VPN traffic can pass through.
sed -i 's/net.ipv4.ip_forward = 0/net.ipv4.ip_forward = 1/g' /etc/sysctl.conf 
sed -i 's/#net.ipv4.ip_forward = 1/net.ipv4.ip_forward = 1/g' /etc/sysctl.conf 
grep -qF "net.ipv4.ip_forward" /etc/sysctl.conf  || echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf

For e.g if the sysctl.conf contain any one of the following it won't match

为e。如果sysctl g。conf包含以下任何一个它不匹配

#net.ipv4.ip_forward=1

# net.ipv4.ip_forward = 1

##net.ipv4.ip_forward=1.

# # net.ipv4.ip_forward = 1。

Is there a more reliable way to modify settings in config files ?

有更可靠的方法来修改配置文件中的设置吗?

3 个解决方案

#1

You can use the -r switch to enable Extended Regular Expressions(ERE) in GNU sed and optionally match the white-space and the # occurence with the regex ? optional item anchor,

您可以使用-r开关来启用GNU sed中的扩展正则表达式(ERE)，并可选择地将空格和#发生率与regex进行匹配。可选的项锚,

sed -ir 's/#{1,}?net.ipv4.ip_forward ?= ?(0|1)/net.ipv4.ip_forward = 1/g' /etc/sysctl.conf

This will match for any of the below input lines and modify it with the replacement part net.ipv4.ip_forward = 1

这将匹配以下任何输入行，并使用替换部分net.ipv4对其进行修改。ip_forward = 1

net.ipv4.ip_forward=0
net.ipv4.ip_forward = 0
#net.ipv4.ip_forward=0
##net.ipv4.ip_forward = 0
#net.ipv4.ip_forward=1
##net.ipv4.ip_forward=1
#net.ipv4.ip_forward = 1
##net.ipv4.ip_forward = 1

See the RegEx Demo for more clarity.

请参阅RegEx演示，以获得更清晰的信息。

#2

What about removing all lines matching net.ipv4.ip_forward, no matter whether commented out or not and then appending what you need?

删除所有匹配的网络。ipv4。ip_forward，无论是否注释掉，然后添加什么?

fgrep -v net.ipv4.ip_forward /etc/sysctl.conf > /etc/sysctl.conf.tmp
echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf.tmp
mv /etc/sysctl.conf.tmp /etc/sysctl.conf

This is simple and readable.

这是简单易读的。

#3

You can use this setting to do it for zero or more spaces and zero or multiple #(comment)

您可以使用这个设置来为0或更多的空格和0或多个#(注释)

sed -i 's/[#| ]*net.ipv4.ip_forward[ ]*=[ ]*0/net.ipv4.ip_forward = 1/g' /etc/sysctl.conf 
grep -qF "net.ipv4.ip_forward" /etc/sysctl.conf  || echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf

#1