insert a string to a list variables in text file [use sed]

Question

I want to add zsh-autosuggestions plugin to ~/.zshrc by script.

original text:

plugins=(git)

or

 plugins=(git
 some1
 some2)

target :

plugins=(git
zsh-autosuggestions)

1. This doesn't work.

   sed -i  's/^plugins=\(([^\)]*)\)/plugins=\(\1\nzsh-autosuggestions\n\)/' ~/.zshrc
   

   I am confused, I think this ([^\)]*) is group 1, but why it not work

2. but remove first group's ()

   sed -i  's/^plugins=\([^\)]*\)/plugins=\(\1\nzsh-autosuggestions\n\)/' ~/.zshrc
   

   turn out to

   plugins=((git
   zsh-autosuggestions
   )
   )
   

   I have escaped the () by \, why it became group 1?

Answer 1

Sed solution:

Sample ~/.zshrc contents:

param=val1
plugins=(git)
param2=val2

plugins=(git
some1
some2)
param3=val3

---

sed '/^plugins=/ N;N; s/\(=([^)]*\))/\1\nzsh-autosuggestions)/' ~/.zshrc

• N - add a newline to the pattern space, then append the next line of input to the pattern space
• \(...\) - regex captured group; should be escaped with \ in BRE to enable its special meaning

---

The output:

param=val1
plugins=(git
zsh-autosuggestions)
param2=val2

plugins=(git
some1
some2
zsh-autosuggestions)
param3=val3

Answer 2

Below command works fine for me

---

Command

 echo "plugins=(git)" | sed "s/(.*[^)]/&\nzsh-autosuggestions/g"

---

Output

plugins=(git
zsh-autosuggestions)