Filling space/tab separated, empty columns with 0

Question

i have a huge file and as an output some columns doesn\'t have a value, i need to fill these columns with 0 for further analysis. I can separate the columns with space or ta

Answer 1

This is really a job for a CSV parser, but if it has to be a regex, and you never have tabs within quoted CSV entries, you could search for

(^|\t)(?=\t|$)

and replace with

$10

So, in Perl:

(ResultString = $subject) =~ 
s/(    # Match either...
   ^   # the start of the line (preferably)
   |   # or
   \t  # a tab character
  )    # remember the match in backreference no. 1
  (?=  # Then assert that the next character is either
   \t  # a(nother) tab character
   |   # or
   $   # the end of the line
  )    # End of lookahead assertion
/${1}0/xg;

This will transform

1   2       4           7   8
    2   3       5   6   7   

into

1   2   0   4   0   0   7   8   
0   2   3   0   5   6   7   0