How to add all values in an array

Question

I have been stuck on this for way to long now. Tried googling and couldn't find what I was looking for.

I simply need to add all the values in an array.(array called packets) I have gotten to the point where I can add them, however when that happens the number value is not able to be called upon later in the script.

Here is the whole script, pretty simple just checking amount of packet data compared to time, aka bandwidth.

rawdata=`tcpdump -nn -S -r test.pcap | awk '{print 1ドル" "$NF}'`
time="`echo "$rawdata" | sed -r 's/(.{15}).*/1円/'`"
starttime="`echo "$time" | awk 'NR > 1 { exit }; 1'`"
endtime="`echo "$time" | awk 'END{print}'`"
stime=`date --date="$starttime" +%s`
etime=`date --date="$endtime" +%s`
difftime="echo $(($etime - $stime))"
echo $difftime
echo $addedpackets
echo $sum
echo ------------------------------------
packets="`echo "$rawdata" | awk '{print 2ドル}' | sed 's/[^0-9]*//g'`"
echo ------------------------------------
for i in "${packets[*]}"
do
 plus=$(printf '%d+' ${i})0
 added="echo $(($plus))"
done
echo ------------------------------------
$added
$difftime
bc -l <<< "$added/$difftime"
echo ------------------------------------

• pabouk - Ukraine stay strong: The variable packets you set on the line 12 is not an array. It is a simple scalar variable.
• Korilic: Oh okay, well is that correct? should I be trying to do maths with scalar variables?

Answer 1

Do the whole thing in awk, shell loops are not the right tool to do this kind of processing:

tcpdump -tt -nn -S -r test.pcap | awk '
 NR == 1 {start = 1ドル}
 {total += $NF}
 END {
 duration = 1ドル - start
 print "total:", total
 print "duration:", duration
 print "average:", total/duration
 }'

Note how that's 2 commands running concurrently as opposed to thousands running in sequence without sharing information in your approach. This one also handles time stamps correctly.

If for some reason, you want those in shell variables, you'd do:

eval "$(
 tcpdump -tt -nn -S -r test.pcap | awk '
 NR == 1 {start = 1ドル}
 {total += $NF}
 END {
 duration = 1ドル - start
 print "total=" total
 print "duration=" duration
 print "average=" total/duration
 }'
)"
echo "$total $duration $average"

• Korilic: This is very nice. Thank You, however how can I now create a variable from the output of awk? Or since I believe that's not possible, how can I simply output all of this to a file?
• Stéphane Chazelas: @user118489, see edit.

Answer 2

To fill the variable packets as an array (single line to a single item) change the line 12 to:

origifs="$IFS"
IFS=$'\r\n'
packets=($(echo "$rawdata" | awk '{print 2ドル}' | sed 's/[^0-9]*//g'))
IFS="$origifs"

to process individual items of the array you have to use @ instead of * at line 14:

for i in "${packets[@]}"

Note: Instead of backticks like `commands` it is preferred to use $(commands).

• pabouk - Ukraine stay strong: Originally I forgot about $IFS. Bash uses the separators from $IFS when splitting the string to the array items. By default it would split also by spaces and tabs. You want to split only by newlines. I have corrected my answer.