Question

I am learning to use sed and have a hypothetical requirement:

bash$ cat states
California


Massachusetts


Arizona

Wisconsin

I would like the output: (Basically I want only one blank line in between)

California

Massachusetts

Arizona

Wisconsin

Please suggest ways to do it with sed.
Should it use concept of multiline pattern space etc.

Thanks,

Jagrati

---

In response to one of the comments, Ok, I ran some test scripts, and I was wrong with hypopthesis that address space selection criteria is applied only once. It seems to get activated again and again.

bash$ cat file 
a 
b 
c 
a 
b 
c 

bash$ sed -e '/a/,/b/s/$/x/g' file 
ax 
bx 
c 
ax 
bx 
c 

I had the impression that it would yield:

ax 
bx 
c 
a 
b 
c

So could someone please explain how the sed proceeds in case of comma separated address spaces.

Answer 1

Try this it will delete all consecutive blank lines

cat states | sed '/./,/^$/!d'

outputs:

California

Massachusetts

Arizona

Wisconsin