Largest number in array. Help!

Shell Programming and Scripting
1

I need to calculate the biggest number in array size n.
Example: Users enter: 1 7 4 9
The biggest number is : 9
Simple but I'm really new on this on Shell/Bash! Anything will be helpful! Thanks!

#!/bin/bash 

printf "\tEnter a list of numbers, with spaces: "
read -a ARRAY

BIG=$1
for i in ${!ARRAY[@]} ; do
    if [ $i -gt $BIG ] ; then
        BIG=$i
    fi
done

echo "Largest number is $BIG"
2

You'll need to populate your array like this:

typeset -a ARRAY
printf "\tEnter a list of numbers, with spaces: "
read  ans
ARRAY=( $ans )

There are other ways, but I think this is easiest.

You need to set big to something real, not $1. Safe to set to first value of the array.

BIG=${ARRAY[0]}

You want to look at aray elements, not the indexes:

for i in ${ARRAY[@]}
1 Like
3

Thanks for the explanation! :b::b: Any good book to start Shell Scripting???

4

Hi folks.

You're right. That's the key.
Just for studying purposes, I've created two bash scripts using different for loop syntax for solving this problem.

Here we go:

#!/opt/local/bin/bash
# rod@wgo.com.br
# get the biggest number in an array of integers

declare -a list # array of integers
declare -i size # size of the array
declare -i biggest # biggest number of the array
declare -i current # current element of the array

read -a list -p "Enter each integer element separated by white spaces: " 
size=${#list[@]}

biggest=${list[0]} # first element of the array is supposed to be the biggest one
for ((i=1; i<$size; i++)); do # loop through the array ( this syntax  is kind of similar to the for loop used by the C programming language )
    current=${list[$i]} # get the current element of the array. This way  you don't have to worry too much about bash syntax for accessing  elements is an array
    if [ $current -gt $biggest ]; then
        biggest=$current
    fi
done

echo -e "\nThe biggest integer number in the array is: $biggest";


#!/opt/local/bin/bash
# rod@wgo.com.br
# get the biggest number in an array of integers

declare -a list # array of integers
declare -i biggest # biggest number of the array
declare -i current # current element of the array

read -a list -p "Enter each integer element separated by white spaces: " 
size=${#list[@]}

biggest=${list[0]} # first element of the array is supposed to be the biggest one
for current in ${list[@]}; do # loop through the array
    if [ $current -gt $biggest ]; then
        biggest=$current
    fi
done

echo -e "\nThe biggest integer number in the array is: $biggest";

Of course, there is more than a way for doing such things.
I suggest you give "Advanced Bash-Scripting Guide" a try. It's a really good and powerful book about Bash Scripting. You may download it for free here:

http://www.tldp.org/guides.html

Hope it helps.

1 Like
5

Thanks a lot!

6

Unless it is for learning purposes, in this case there is no need for arrays.

BIG=0
printf "\tEnter a list of numbers, separated by spaces: "
read list
for i in $list; do
  if [ $i -gt $BIG ]; then
    BIG=$i
  fi
done
printf "%s\n" "Largest number is $BIG"