Replacing missing value blank space with zero

Question

I have input.txt tab-delimited text file around 30K lines, I would like to check each row (s1..s30K lines) for missing value (i.e blank space) and fill the missing value with zero value.See out.txt

input.txt

 id  no1  no2  no3  no4
 s1  23   34   45   12
 s2       4    4      
 s3  4         8    0

out.txt

id  no1  no2  no3  no4
s1  23   34   45   12
s2  0     4    4    0  
s3  4     0    8    0

Answer 1

You could do it like this with awk:

awk 'BEGIN { FS = OFS = "\t" } { for(i=1; i<=NF; i++) if($i ~ /^ *$/) $i = 0 }; 1' file

Explanation

Setting FS and OFS to tab ensures the output is correctly delimited. The for-loop looks at every field and sets it to zero if it is empty. The one at the end is a shorthand for { print $0 }.

Answer 2

I'd prefer:

sed 's/<TAB> /<TAB>0/g' <input.txt >output.txt

Replace <TAB> with the real TAB character (generally obtained by hitting Ctrl-V, then Tab)