I am getting error in nested elif statement in shell scripting-CodePudding

I am preparing shell code for comparing 3 numbers. My code is as follows

#!/bin/bash

echo "enter any 3 numbers"
read num1
read num2
read num3

if [ $num1 -gt $num2 ]
  then
     if [ $num1 -gt $num3 ]
      then 
        echo "$num3 is greater than $num1 & $num1"
      fi
elif [ $num2 -gt $num1 ]
  then 
     if [ $num2 -gt $num3 ]
      then 
         echo "$num2 is greater than $num1 & $num3"
     fi
elif [ $num3 -gt $num1 ]
  then
     if [ $num3 -gt $num2 ]
       then
         echo "$num3 is greater then $num2 &$num1"
     fi
else
   echo "invalid"
fi

if i put 1st or 2nd highest number then it is giving right output,But in case if i put 3rd higest number it is not evaluating.Second elif statement is not getting evaluated.

CodePudding user response：

Let's make this more readable first:

if [ $num1 -gt $num2 ]; then
    if [ $num1 -gt $num3 ]; then
        echo "$num1 is greater than $num2 & $num3" # typos fixed
    fi
elif [ $num2 -gt $num1 ]; then
    if [ $num2 -gt $num3 ]; then
        echo "$num2 is greater than $num1 & $num3"
    fi
elif [ $num3 -gt $num1 ]; then
    if [ $num3 -gt $num2 ]; then
        echo "$num3 is greater then $num1 & $num2" # typos fixed
    fi
else
    echo "invalid"
fi

If you enter e.g. num1 == 1, num2 == 2, num3 == 3, then it won't work because this is true:

elif [ $num2 -gt $num1 ]; then

but after that, this is false:

if [ $num2 -gt $num3 ]; then

thus there is no output. Execution will not continue with elif [ $num3 -gt $num1 ]; then if that is what you expected, ifs don't work like that.

You could restructure it like this:

if [ $num1 -gt $num2 ] && [ $num1 -gt $num3 ]; then
    echo "$num1 is greater than $num2 & $num3"
elif ...

and continue adding elifs until all possible permutations and cases are covered.

CodePudding user response：

This is a lot simpler if you just make two comparisons at once:

if [ "$num1" -gt "$num2" ] && [ "$num1" -gt "$num3" ]; then
    echo "$num1 is greater than $num2 and $num3"
elif [ "$num2" -gt "$num1" ] && [ "$num2" -gt "$num3" ]; then
    echo "$num2 is greater than $num1 and $num3"
elif [ "$num3" -gt "$num1" ] && [ "$num3" -gt "$num2" ]; then
    echo "$num3 is greater than $num1 and $num2"
# else echo "no one number is biggest"
fi