Is it possible to insert new column in input file using awk?

Question

My input file is as below

file name: marksheet

No         Name       Sub1     Sub2    Sub3
1          Atul       89        56      78
2          Jay        56        88      75
3          Mariya     85        75      56
4          Nita       90        88      95

Now i want to perform total and percentage. So i performed below command

awk 'total=$3+$4+$5, per=total/3 {print total "\t" per}' marksheet

it gives output of total and column. as

223       74.3333
219       73
216       72
273       91

So now i want to add above column( output) in file marksheet. So if it is possible then how to perform the command using awk.

Answer 1

As I had never used the -i switch and inplace editing (in Gnu awk since v. 4.1.0 (gawk -V), according to awk save modifications in place) I decided to take it for a spin. I took OP's example data and code and went with it:

$ awk -i inplace -v INPLACE_SUFFIX=.bak 'NR==1 && $6="total", $7="per"; NR>1 && $6=$3+$4+$5, $7=$6/3' OFS='\t' file
$ cat file
No      Name    Sub1    Sub2    Sub3    total   per
1       Atul    89      56      78      223     74.3333
2       Jay     56      88      75      219     73
3       Mariya  85      75      56      216     72
4       Nita    90      88      95      273     91

And the backup:

$ cat file.bak
No         Name       Sub1     Sub2    Sub3
1          Atul       89        56      78
2          Jay        56        88      75
3          Mariya     85        75      56
4          Nita       90        88      95

Spacing difference comes from real tabs in output vs. cut'n pasting the question for input.

Answer 2

Begin statement is to define header of the file. you have already calculated sum and average. Printed $0 means whole line and then total and then per variables which contains value of sum and average value. OFS here make awk aware of the output fields to be separated using tab.

awk  -v OFS="\t" 'BEGIN{print "No         Name       Sub1     Sub2    Sub3    total    percent"} NR>1{total=$3+$4+$5; per=total/3 ;print $0 ,total,per }' marksheet
No         Name       Sub1     Sub2    Sub3     total   percent
1          Atul       89        56      78      223     74.3333
2          Jay        56        88      75      219     73
3          Mariya     85        75      56      216     72
4          Nita       90        88      95      273     91  

To actually modify your base file:

awk  -v OFS="\t" 'BEGIN{print "No         Name       Sub1     Sub2    Sub3    total    percent"} NR>1{total=$3+$4+$5; per=total/3 ;print $0 ,total,per }' marksheet >marksheet.tmp && mv marksheet.tmp marksheet