Largest number in array. Help!


 
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# 1  
Old 03-21-2012
Lightbulb Largest number in array. Help!

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!

Code:
#!/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  
Old 03-21-2012
You'll need to populate your array like this:

Code:
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 $1. Safe to set to first value of the array.
Code:
BIG=${ARRAY[0]}

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

Code:
for i in ${ARRAY[@]}

This User Gave Thanks to agama For This Post:
# 3  
Old 03-21-2012
Quote:
Originally Posted by agama
You'll need to populate your array like this:

Code:
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 $1. Safe to set to first value of the array.
Code:
BIG=${ARRAY[0]}

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

Code:
for i in ${ARRAY[@]}

Thanks for the explanation! SmilieSmilie Any good book to start Shell Scripting???
# 4  
Old 03-21-2012
Hi folks.
Quote:
You need to set big to something real, not $1. Safe to set to first value of the array.
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:

Code:
#!/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";

Code:
#!/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:
Code:
http://www.tldp.org/guides.html

Hope it helps.
This User Gave Thanks to chapeupreto For This Post:
# 5  
Old 03-22-2012
Thanks a lot!
# 6  
Old 03-22-2012
Unless it is for learning purposes, in this case there is no need for arrays.

Code:
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"

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