regex - How to turn newlines into indents with regular expressions -

i have list looks this:

item 1   subitem 1  item 2  item 3   subitem 1   subitem 2    subsubitem 1  item 4 

pretty much, every top-level item has 1 newline before it, , each subitem has 2 newlines, , sub-subitems have three, , on. want in format similar this:

item 1     subitem 1 item 2 item 3     subitem 1     subitem 2         subsubitem 1 item 4 

the regex have been using in vim this:

for first level:

%s/^$\n\(\t\w\)/\t\1/g 

for second level:

%s/^$\n\(\t\t\w\)/\t\1/g 

and on.

what's better way without having run different regex each level of list? i'm trying use vim this, *nix solution fine me.

one thing can recursively use following regex :

(?<!\n)\n\t*\n 

recursively find , replace occurrence of regex

• first pass replace : \n
• second pass replace : \n\t
• third pass replace : \n\t\t
• fourth pass replace : \n\t\t\t

...and on until there no match regex anywhere.

so don't have run different regex every time, still you'll have change replace part. can write small program recursively it.