CODEWITHSUNDEEP
pythonbashshellawk
Sanchit J R
Sanchit J R

Reputation: 87

How can I get absolute difference of two numbers?

Is there any bash/shell command to get absolute difference of two numbers? Eg.-

Absolute diff of -10 and -5 is 5, -10 and 10 is 20, 7 and 21 is 14 & 100 and -11 is 111.

Or any workaroud to find it? Please help.

Upvotes: 1

Views: 10624

Answers (6)

Feriman
Feriman

Reputation: 627

You can do that without any external command by using ${var#-}.

${var#Pattern} Remove from $var the shortest part of $Pattern that matches the front end of $var. tdlp

Example:

s2=7; s1=8
s3=$((s1-s2))

echo $s3
-1

echo ${s3#-}
1

Upvotes: 0

Jan
Jan

Reputation: 2273

This works for non-integer numbers also using bc.

function abs_diff {
    if [ $(bc <<<"$1 >= $2") -eq 1 ]; then
        diff="$(echo $1 - $2 | bc)"
    else
        diff="$(echo $2 - $1 | bc)"
    fi
    
    echo $diff
}

abs_diff 5.0 1.0  #gives output: 4.0
abs_diff 1.0 5.0  #gives output: 4.0

Upvotes: 0

5gon12eder
5gon12eder

Reputation: 25419

You can do simple integer arithmetic directly in the shell using the $((...)) syntax.

function abs_diff {
    local diff
    diff=$(($1 - $2));
    if [ $diff -lt 0 ]
    then
        diff=$((-$diff))
    fi
    echo $diff
}

It can be written more tersely as a single expression using the ternary ? operator.

function abs_diff {
    echo $(($1 >= $2 ? $1 - $2 : $2 - $1))
}

Then simply use

abs_diff -10 -5

in your code.

Update: “It would be great if you could explain the logic.” — There we go…

The basic idea is that we write a Bash function that takes two integers as arguments and returns the absolute difference of them.

A Bash function can be called like an external program using the FUNCTION_NAME [ARG...] syntax. Inside a function, we can refer to its arguments via $1, $2, … just as we refer to a shell script's arguments outside of any function. To “return” a value from a function, we print it to standard output. (Don't abuse the return statement for that. It is intended to report success or failure, not business data.) If we want to assign the result of a function call to a variable, we can use the VAR=$(COMMAND [ARG...]) syntax. A function definition has the syntax function FUNCTION_NAME { FUNCTION_BODY }. If we declare variables that should be local to a function, we can use the local keyword. This is a Bash feature.

Now let's see how we can compute the absolute value of the difference. We only have integer arithmetic so how can we do it? Obviously, if we subtract an integer n from an integer m, there are only two possible outcomes: a non-negative or a negative result. In the first case, we are done. In the second, all we need to do is to take the negative.

The first function does exactly this.

function abs_diff {           # Define the function 'abs_diff'
    local diff                # with 'diff' as a local variable
    diff=$(($1 - $2));        # to compute the difference of its first two arguments
    if [ $diff -lt 0 ]        # and if it is negative
    then                      # then
        diff=$((-$diff))      # negate the result
    fi                        # and
    echo $diff                # finally print the result.
}

The second version is more terse. If you know the ternary ? operator for example from C or Java, then it will come at no surprise. What this line

echo $(($1 >= $2 ? $1 - $2 : $2 - $1))

means is: If $1 >= $2 evaluates to true, then print $1 - $2, otherwise $2 - $1, which ensures that the result will always be non-negative.

If your need is a one-time thing and defining a function seems like overkill to you, simply copying the body of the second function to the place where it is needed might be a viable alternative.

Upvotes: 4

midori
midori

Reputation: 4837

Here is the simple one:

echo $(($1-$2)) | sed 's/-//'
./script.sh -10 -5

output

5

The logic is pretty simple. You provide parameters $1 and $2 to your script like ./script.sh -10 -5 and then output result of $1 - $2 using echo. sed will delete - if it is presented.

Upvotes: 6

vikramls
vikramls

Reputation: 1822

How about this bash implementation:

export A=5
export B=10
echo "$A-$B" | bc | tr -d -

Output:

5

Upvotes: 2

thefourtheye
thefourtheye

Reputation: 239483

You can execute Python commands, from the command line with -c parameter. So, you can make use of it, like this

python -c "import sys; print(abs(int(sys.argv[1]) - int(sys.argv[2])))" 100 -11
# 111

This script gets two arguments from the command line, converts both of them to integers, subtracts second value from the first value and prints the absolute value of the result

Upvotes: 2

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