Scripting number evaluation

dotmil · 11-03-2012, 11:41 AM

I've been trying to come up with a way to do this in a Bash script and haven't been able to get the expected results. I'm hoping someone much more experienced than myself has a pointer.

In a nutshell, I'm reading from a file with 2 space separated columns, column1 is user names, column2 is an integer of 1 to 6 digits long. What I need to do is evaluate the number and perform one action if it is greater than $NUM. The username must also be associated with the results.

In other words, if the value in column 2 is > $NUM, then output the complete line. If less than $NUM, just continue on to the next line. Any suggestions on how to do this in a sane and scaleable way if the list to be evaluated is quite long?

rigor · 11-03-2012, 12:16 PM

If I'm understanding you correctly, your data looks something like this:

Code:

John_Doe 5
Jane_Smith 6
Peter_Jones 7

I'm not sure I'd use a bash script to handle a truly long file, there are probably other languages other than bash script language that might be faster, but if your data looks something like the above, why wouldn't a bash script like the following work?

Code:

if [  $#  -eq  1  ]
    then

        comparator="$1"

        while read user_name number
            do
                if [  $number  -gt  $comparator  ]
                    then
                        echo "$user_name $number"
                fi
            done

    else

        echo "Usage: ${0} number_for_comparison"
fi

H_TeXMeX_H · 11-03-2012, 12:54 PM

I would use awk:

Code:

x=6
awk -v num=$x '{ if ($2 > num) print}' test.txt

dotmil · 11-04-2012, 12:25 AM

Thanks guys. The awk solution fit best for me for now. Awesome :-)

grail · 11-04-2012, 06:31 AM

Just to provide some more information on the awk solution, you can represent the data in 3 different ways using the same example:

Code:

# Original from H_TeXMeX_H
awk -v num=6 '{ if ($2 > num) print}' test.txt

# Using the if expression to give brace access
awk -v num=6 '$2 > num{print}' test.txt

# And lastly to use default action of a true evaluated expression to print
awk -v num=6 '$2 > num' test.txt