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preserving last read value in shell script

Dear ALL,

Here are the contents of the file
1600
1900
2200
2800

I want to read file content using shell script
and check if the difference between the two line count is 300

With regards,
Keerti

Hi,

Code:

#!/bin/bash



PrevValue="-1"



for ThisValue in $(cat infile)

do

  if [ ! $PrevValue = "-1" ]

  then

    let SubtValue=ThisValue-PrevValue

    if (( SubtValue == 300 ))

    then

      echo "difference is 300 ($ThisValue - $PrevValue)"

    else

      echo "difference is not 300 ($ThisValue - $PrevValue)"

    fi

  fi

  let PrevValue=ThisValue

done

Hope this helps.

Or another option:

Code:

awk 'NR > 1{printf "Difference is %s300\n",($0 - x == 300)?"":"not "}{x = $0}' file

Thanks druuna,it worked for me

I created a script named readfile and a test data file named testdata. Testdata contains all the data in your sample.

Code:

#!/bin/bash

read var1

echo "variable 1 is: $var1"

let var3=0

echo "Variable 3 is: $var3"

let check=0



while read var2 ; do

  echo "Variable 2 is: $var2"

  var3=$(expr $var2 - $var1)

  echo "Variable 3 is computed as var2 - var1: $var3"

  let var1=var2

  echo "Variable 1 now set to value of variable 2"

  echo "Variable 1 is $var1 Variable 2 is $var2 Variable 3 is $var3"

  echo "loop for more records"

done



echo "Read completed"

Note: I don't do testing to verify the data, I'm assuming you know how to do that. This script simply shows the process of reading the data and uses echo to display messages and values that demonstrate the process the loop is going through.

Hope this helps!

Roger