UNIX for Dummies Questions & Answers

Ive been trying to slide the second column one line down while keeping the first one in place. For a start, I tried to see if I can go through every line and print the element located on the line below with the following command, but it didnt work.
Maybe awk is not the right way to do it. Matlab can do this easily, but if there is a way to do this in unix, I'd highly appreciate it. thank you!

awk '{for(i=1; i<NR; i++) FNR==i {print i, $(i+1)}}' filename.txt

It would help to supply some input, using code tags, and show your expected output.

Okay, trying. thank you
Input:
7 1
49 0
83 0
5 2
42 0

Hopeful output:
7 0
49 0
83 0
5 2
42 0

I don't get it. You talked about changing the next line down, but all you have done here is change the 1 in the 2nd field of the 1st line to a zero. Nothing else changed??? You said you wanted to keep the first one in place, but the first 1 is the only thing that you changed???

In your output you only replaced the 2nd field in the 1st line
From your text I understand output should be
7 0
49 1
83 0
5 0
42 2

That would be

Code:

awk '{print $1+0,save+0} {save=$2}'

Indeed, this is what I meant. Fantastic, this worked! Thank you.

FYI, the awk code is executed left to right for each line(row).
A loop can hardly span over many lines (unless readline is used to "read ahead" but this often gets ugly).
Here the variable save stores the field2 at the current line, to be printed at the next line. (Initially save is "" or 0, casted to integer 0 by adding 0. Another method is to initialize with BEGIN {save=0}).