How to subtract values of two columns and add to a new column in text file using awk/bash script

user_17245599 0
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I want to subtract the values from two columns and add result into a new column (at the very end) using awk or bash. the data is in a txt file.

I tried

awk 'BEGIN {OFS="\t"} NR == 1 {$20 = "tr_pe"} NR >=2 {$20= $5-$11}1' <filename

or

awk OFS="\t" \{$(NF+1)=$5-$11}1' filename.txt

The first code did the subtraction but saved it in column 2 instead of at the end, and I realised that it actually did not get saved to the txt.file. Second one did some calculation but it was not accurate

What I want to do - subtract values from column 5 with column 11 and save it under header tr_pre (which falls into column 20 at the end of all the 19 columns in the file). Columns are separated by tab.

awk bash
3 Answers

You could use next after line 1 to continue the iteration. To print the result at the end, you can print the whole line using $0 followed by the value that you want at the end.

cat filename.txt

c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 c13 c14 c15 c16 c17 c18 c19
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

For example

awk 'BEGIN {OFS="\t"}
{$1=$1}
NR == 1 {
  print $0, "tr_pre"
  next
} 
{
  print $0, $5-$11
}' filename.txt > output.txt

output.txt

c1  c2  c3  c4  c5  c6  c7  c8  c9  c10 c11 c12 c13 c14 c15 c16 c17 c18 c19 tr_pre
1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16  17  18  19  -6
user_54249880

Based on your description, this should solve your problem.

awk 'BEGIN {FS=OFS="\t"} NR == 1 {print $0, "tr_pre"} NR >=2 {print $0, $5 - $11}' filename.tsv > file_with_new_tr_pre_column.tsv

If there are other confounding factors, please provide a minimal reproducible example

user_129573400 
$ awk '{print $0 "\t" (NR==1?"tr_pre":$5-$11)}' oldfile > newfile
user_14358690
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