Bash sum of array

Question

I'm writing script in Bash and I have a problem with sum elements of array. I add to array results of df for two paths. In result I want to get sum elements of array.

use=()
i=0
for d in '$PATH1' '$PATH2'
do 
    usagebck=$(du $d | awk '{print awk $1}')
    use[i]=$usagebck
    sum=0
    for j in $use
    do
             sum=$($sum + ${use[$i]})

    done

    i=$((i+1))

done
echo ${use[*]}

Variables do not expand in single quotes. So '$PATH' is the literal string $PATH. — Etan Reisner
– Etan Reisner, Commented Dec 24, 2014 at 14:30
There's also no reason to have the usagebck variable in this script as-written. And $use will only give you the first value in the array. — Etan Reisner
– Etan Reisner, Commented Dec 24, 2014 at 14:31
Do you actually have a directory name $PATH1, or do you not understand the difference between single quotes and double quotes? You probably meant to write for d in "$PATH1" "$PATH2" — William Pursell
– William Pursell, Commented Dec 24, 2014 at 16:51

Cyrus · Accepted Answer · 2014-12-24 15:30:05Z

3

If your du has option -s:

use=()
sum=0
for d in "$PATH1" "$PATH2"
do
  usagebck="$(du -s "$d" | awk 'END{print $1}')"
  use+=($usagebck)
  ((sum+=$usagebck))
done
echo ${use[*]}
echo $sum

edited Dec 24, 2014 at 15:30

answered Dec 24, 2014 at 14:54

Cyrus

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1 Comment

chepner Over a year ago

There's no reason to prefer ${use[*]} over "${use[@]}" here.

David W. · Accepted Answer · 2014-12-24 16:18:03Z

First, take a look at the parameters in du. On BSD based systems, there's -c which will give you a grand total. On GNU and BSD, there's the -a parameter which will report on all files for a directory.

Since you're already using awk, why not do everything in awk?

$ du -ms $PATH1 $PATH2 | 
  awk 'BEGIN {sum = 0} 
       END {print "Total: " sum } 
       {
           sum+=$1
           print $0
       }'

du -ms specifies that I want the total sums of each file specified
BEGIN is executed before the main awk program. Here I'm initializing sum. This isn't necessary because variables are assumed to equal zero when created.
END is executed after the main awk program. Here, I'm specifying that I want sum printed.
Between the { ... } is the main Awk program. Two lines. The first line adds Column 1 (the size of the file) to sum. The second line prints out the entire line.

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