How can i create a Linux Script (bash, sed, awk…) to add a line in a specific section of a configuration's file

Question

I need make a script with Linux common tools (Bash, awk, sed,...) to edit a configuration file in a style like INI, that is:

[sectionA]
var1=x
var2=y
#...

[sectionB]
var1=x
var2=y
#...

[sectionC]
var1=x
var2=y
#...

I need add a line in a specific section, that is, find a part that start with a line "[sectionX]" and append a line BEFORE the next new line or EOF. How can I do this?

Answer 1

sed -i '/^\[sectionB\]/a\append your line here' my_file

or

sed -i '/^\[sectionB\]/s/$/\nappend your line here/' my_file

example appending a line to [sectionB] using either command line above

the output

[sectionA]
var1=x
var2=y
#...

[sectionB]
append your line here
var1=x
var2=y
#...

[sectionC]
var1=x
var2=y
#...

Answer 2

sed -e 's/\(\[sectionB\]\)/\1\nvar_new=value/' -i file.ini

请注意，如果file.ini已经有定义var_new=something_else的行，则需要单独删除它。

Answer 3

You can do this with gnu awk

awk -vRS= -vORS="\n\n" -F"\n" -vOFS="\n" '/sectionB/ {$1=$1"\nnew=42"}1' file
[sectionA]
var1=x
var2=y
#...

[sectionB]
new=42
var1=x
var2=y
#...

[sectionC]
var1=x
var2=y
#...

Search for sectionB then add new=42 in that section.

Answer 4

您可以使用crudini更加健壮/轻松地编辑文件

crudini --set file 'sectionB' new 42