Bash 'while read line' into an array and sum total

Question

I hope someone can help...

I've parsed integers to a file separated by carriage returns like so:

...
427562786
6834257
978539857
9742
578375
...

I wish to put these into an array and sum the total. However, after some fervent Googling, I can only find a reasonable way to do this using a for loop, which I'm on pretty good authority is not the best way to read a file line by line.

I understand that somewhere in this script I would need to declare something like this:

IFS='
'
while read line
do
array creation magic here
done < /tmp/file

SUM=0
while read line
do
SUM= sum array elements magic here
done < /tmp/file

printf $SUM

Please can someone more knowledgeable than me let me know what I'm missing? Thanks. :)

Chris · Accepted Answer · 2012-08-22 10:28:18Z

2

If the array is only an intermediate step and not required beyond that point then this takes you straight to the final answer:

sum=0
while read N
do
    # sum=$((sum+N)) - the line below shows a more concise syntax
    ((sum += N))
    echo "Added $N to reach $sum"
done < /tmp/list_of_numbers

echo $sum

edited Aug 22, 2012 at 10:28

answered Aug 22, 2012 at 9:59

Chris

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1 Comment

Chris Over a year ago

I've tweaked the syntax to a more concise form (see tldp.org/LDP/abs/html/arithexp.html)

chepner · Accepted Answer · 2012-08-22 13:06:56Z

1

In bash 4, there is the mapfile command.

mapfile -t numbers < /tmp/list_of_numbers

for n in "${numbers[@]}"; do
    (( sum += n ))
done

In earlier versions of bash, you can use read, but it's a little more verbose:

IFS=$'\n' read -d '' -a numbers < /tmp/list_of_numbers

edited Aug 22, 2012 at 13:06

answered Aug 22, 2012 at 12:42

chepner

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