Use sed and regex to replcae sections of a configuration file

April 13, 2022

I have a configuration file structured as follows:

[section1]
path = <path1>
read only = yes
guest ok = yes

[section2]
path = <path2>
read only = no
guest ok = yes

I would need to be able to replace a whole section of the configuration file with a new section using the sed command.
Example of what I would like to achieve:

sudo sed -E -i ':a;N;$!ba;\[section1\]<regex_match_until_end_of_section1>/<new_section_1>/' <config_path>

Expected result:

<new_section_1>

[section2]
path = <path2>
read only = no
guest ok = yes

sudo sed -E -i ':a;N;$!ba;\[section2\]<regex_match_until_end_of_section2>/<new_section_2>/' <config_path>

Expected result:

[section1]
path = <path1>
read only = yes
guest ok = yes

<new_section_2>

>Solution :

While sed may be able to do this but using awk is much more intuitive and clean:

awk -v s='[section1]' -v RS= '$1 == s {$0 = "<new_section_1>"}
{ORS=RT} 1' file

<new_section_1>

[section2]
path = <path2>
read only = no
guest ok = yes

Or:

awk -v s='[section2]' -v RS= '$1 == s {$0 = "<new_section_2>"} 
{ORS=RT} 1' file

[section1]
path = <path1>
read only = yes
guest ok = yes

<new_section_2>