Difference between two rows

Shell Programming and Scripting
1

Dears,

I have a list as follows,

2
4
8

If I want to find the difference between two consecutive rows. Then I have to store the specific rows in two variables and then find the difference. Could someone tell how this can be done.

Regards,

2

You can use this poor script:

#!/bin/sh
x="1"
if [ $1 != "" ]; then
a=`sed -n '$x,$xp' $1`
x=$(($x+1))
b=`sed -n '$x,$xp' $1`
fi
if [ $a = $b ];then
echo "ok"
else
echo "no"
fi

However this scrip is just a stupid! You can write something similar with "while" and better.

3

Converting absolute to relative and vice versa is a very common requirement.
There really should be a standard tool for it, hmm....
Anyway here's a python script I use:

#!/usr/bin/env python
                                                                                
import sys
                                                                                
prev=0
while 1:
    line = sys.stdin.readline()
    if line == '':
        break
    try:
        cur = float(line)
        print cur - prev
        prev = cur
    except:
        pass
4

nawk '{print $0-prev; prev=$0}' listFile

NOTE: pixelbeat, I think you've replied to the wrong thread.

5

No I didn't. I was just speaking in more general terms.

6

vgersh99, is right

7

2
4
2

2-4=-2
4-2=2

'difference' != absolute

8

vgersh99 your method is correct.

Regards