How to add the sum of any column value to the last column of the last record in a tab delimited file

Question

I need to take the sum of col2 and add the value to the last column of the last record. Please advice on how we can achieve this using the UNIX shell script.

Eg Input file: Col1 Col2 Col3 Col4 abc 2 A null bcd 3 B null adf 4 C null Output file Col1 Col2 Col3 Col4 abc 2 A null bcd 3 B null adf 4 C 9 

Answer 1

Assuming you want to keep a space in your output:

 $ awk '{sum+=$2; s=s $0 ORS} END{ sub("null"ORS"$",sum,s); print s}' file Col1 Col2 Col3 Col4 abc 2 A null bcd 3 B null adf 4 C 9 

or

 $ awk '{sum+=$2; printf "%s",p} {p=$0 ORS} END{ sub("null$",sum); print}' file Col1 Col2 Col3 Col4 abc 2 A null bcd 3 B null adf 4 C 9 

Answer 2

This awk script will do this, I think:

 awk '{sum+=$2; if (NR != 4) print; } END {$4=sum; print;}' infile 

EDIT: Or even better:

 awk '{sum+=$2; if (NR>1) print x; x=$0} END {$4=sum; print $0;}' infile 

Answer 3

Here is one way: GNU awk :

 awk -v last="$(wc -l < file.txt)" 'NR == 1 { print; next } { sum += $2 } NR == last { sub($NF, sum) }1' file.txt 

Results:

 Col1 Col2 Col3 Col4 abc 2 A null bcd 3 B null adf 4 C 9