Extract the last three columns from a text file with awk - bash

Question

I have a .txt file like this:
ENST00000000442 64073050 64074640 64073208 64074651 ESRRA
ENST00000000233 127228399 127228552 ARF5
ENST00000003100 91763679 91763844 CYP51A1
I want to get only the last 3 columns of each line.
as you see some times there are some empty lines between 2 lines which must be ignored. here is the output that I want to make:
64073208 64074651 ESRRA
127228399 127228552 ARF5
91763679 91763844 CYP51A1
awk  '/a/ {print $1- "\t" $-2 "\t" $-3}'  file.txt.
it does not return what I want. do you know how to correct the command?

Answer 1

Following awk may help you in same.
awk 'NF{print $(NF-2),$(NF-1),$NF}' OFS="\t" Input_file
Output will be as follows.
64073208 64074651 ESRRA
127228399 127228552 ARF5
91763679 91763844 CYP51A1
EDIT: Adding explanation of command too now.(NOTE this following command is for only explanation purposes one should run above command only to get the results)
awk 'NF ###Checking here condition NF(where NF is a out of the box variable for awk which tells number of fields in a line of a Input_file which is being read).
###So checking here if a line is NOT NULL or having number of fields value, if yes then do following.
{
print $(NF-2),$(NF-1),$NF###Printing values of $(NF-2) which means 3rd last field from current line then $(NF-1) 2nd last field from line and $NF means last field of current line.
}
' OFS="\t" Input_file ###Setting OFS(output field separator) as TAB here and mentioning the Input_file here.

Answer 2

You can use sed too
sed -E '/^$/d;s/.*\t(([^\t]*[\t|$]){2})/\1/' infile

Answer 3

With some piping:
$ cat file | tr -s '\n' | rev | cut -f 1-3 | rev
64073208 64074651 ESRRA
127228399 127228552 ARF5
91763679 91763844 CYP51A1
First, cat the file to tr to squeeze out repeted \ns to get rid of empty lines. Then reverse the lines, cut the first three fields and reverse again. You could replace the useless cat with the first rev.