1

Okay here is my code you can probably get the jist of what I'm trying to do. I'm not that good with Linux bash.

#random numbers
MAXCOUNT=100
count=1


while [ "$count" -le $MAXCOUNT ]; do
    number[$count]=$RANDOM
    let "count += 1"
done

#adding function
function sum()
{
    echo $(($1+$2))
}

#main section
first="${count[1-20]}"
echo "The sum of the first 20 elements are: $first"
last="${count[1-20]}"
echo "The sum of the last 20 elements is: $last"

if [ $first -gt $last ]; then
    echo "The sum of the first 20 numbers is greater."
else
    echo "The sum of the last 20 numbers is greater."
fi

My goals with this script:

  • Get and echo the sum of the first 20 numbers of the array containing randoms numbers.

  • Get and echo the sum of the LAST 20 numbers of the array containing randoms numbers.

  • Echo whether the first sum is greater than the second sum.

Any help would this would be great! Bash please.

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3 Answers 3

Reset to default
3

Let's start with the sum function. We actually want to make it a bit more generalized -- make it add up ALL arguments so we can get rid of a couple of loops doing something like reduce func array.

# Since you are using bash, let's use declare to make things easier.
# Don't use those evil `function foo` or `function foo()` stuffs -- obsolete bourne thing.
sum(){ declare -i acc; for i; do acc+=i; done; echo $acc; }

The rest is quite easy.

MAXCOUNT=100 num=()
# Let's use the less evil native 0-based indices.
for ((i=0; i<MAXCOUNT; i++)); do nums+=($RANDOM); done

# https://gnu.org/software/bash/manual/bashref.html#Shell-Parameter-Expansion
# set f to the sum of the 20 elements of nums starting from elem 0
f=$(sum "${nums[@]:0:20}"); echo f20=$f
# set l to the sum of the LAST 20 elems of nums, mind the space
l=$(sum "${nums[@]: -20}"); echo l20=$l
if ((f > l)); then echo f20g; else echo l20g; fi
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3
  • At the end on f20g, and l20g what is the "20g" for? Commented Dec 5, 2015 at 22:16
  • @DavidPrentice Just too lazy to type those 'last 20 blah greater' thing. Commented Dec 5, 2015 at 22:19
  • Okay well it is taking me a bit to digest this, but you 100% answered my question. Commented Dec 5, 2015 at 22:25
2 
unset  num[@] sum; c=-1
while  num[c+=1]=$RANDOM
do     case $c  in      ([2-7]?) ;;
       ($((sum+=num[c])):|99) ! eval '
               printf "$@$sum" "$'"$((sum<$3?2:4))\" greater";;
       (19)    set "The sum of the %-5s 20 elements is:\t%s\n" \
                    first "$sum" last "";  sum=0
       esac||break
done

The sum of the first 20 elements is:    308347
The sum of the last  20 elements is:    306596
The sum of the first 20 elements is:    greater
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2

Another possible solution:

#!/bin/bash

        max=100 rng=20   ### Problem conditions

texta="The sum of the %.3sst %d elements is: %d\n"      ### Output
textb="The first sum is %ser than the last sum\n"       ### Output

unset   num                                             ### used vars
for     (( s1=s2=c=0 ;  c<max ; c++ ))
do      num[c]=$RANDOM
        (( c<rng      )) && (( s1+=num[c] ))            ### first sum.
        (( c>=max-rng )) && (( s2+=num[c] ))            ### last sum.
done

    compare=small; (( s1 > s2 )) && compare=bigg

    printf "$texta" "first" "$rng" "$s1"
    printf "$texta" " last" "$rng" "$s2"
    printf "$textb" "$compare"

The sum of the first 20 elements is: 348899
The sum of the  last 20 elements is: 336364
The first sum is bigger than the last sum
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