Shortest command to calculate the sum of a column of output on Unix?

ipcs -mb | tail +4 | awk '{ sum += $7 } END { print sum }'

Or without tail:

ipcs -mb | awk 'NR > 3 { sum += $7 } END { print sum }'

Using awk with bc to have arbitrary long results (credits to Jouni K.):

ipcs -mb | awk 'NR > 3 { print $7 }' | paste -sd+ | bc

I have a utility script which simply adds up all columns. It's usually easy enough to grab the one you want from the one-line output. As a bonus, some SI-suffixes are recognized.

#!/usr/bin/awk -f
# Sum up numerical values by column (white-space separated)
#
# Usage:  $0 [file ...]
#
# stern, 1999-2005

{
    for(i = 1; i <= NF; ++i) {
        scale = 1
        if ($i ~ /[kK]$/) { scale = 1000 }
        if ($i ~ /[mM]$/) { scale = 1000*1000 }
        if ($i ~ /[gG]$/) { scale = 1000*1000*1000 }
        col[i] += scale * $i;
    }
    if (NF > maxnf) maxnf = NF;
}

END {
    for(i = 1; i <= maxnf; ++i) { printf " %.10g", col[i] }
    print "";
}

Example with custom field separator:

$ head /etc/passwd | addcol -F:
0 0 45 39 0 0 0

Python Solution

#!/usr/bin/env python
text= file("the_file","r")
total= 0
for line in text:
    data = line.split()
    if data[0] in ('T', 'Shared', 'IPC'): continue
    print line
    segsize= int(data[6])
    total += segsize
print total

Most Linux distros have Python.

If you want to process stdin as part of a pipline, use

import sys
total = 0
for line in sys.stdin:
   ...etc...

If you want to assume that there's always 3 header lines:

import sys
total = 0
for line in sys.stdin.readlines()[3:]:
    total += int(line.split()[6])
print total

One-liner:

import sys; print sum( [int(line.split()[6]) for line in sys.stdin.splitlines()[3:]] )

You could start by running the data through cut - which would at least trim the columns down.

You should then be able to pipe that into grep, stripping-out non-numerics.

Then ... well, then I'm not sure. It might be possible to pipe that to bc. If not, it could certainly be handed to a shell script to add each item.

If you used tr to change the newlines (\n) to spaces (), and piped that through xargs into your script that loops until there are no more inputs, adding each one, you may have an answer.

So, something akin to the following:

cat <whatever> | cut -d'\t` -f7 | grep -v <appropriate-character-class> | tr '\n' ' ' | xargs script-that-adds-arguments

I may have the cut flags slightly wrong - but man is your friend :)

You could look it up in any online awk reference:

ipcs | awk '
BEGIN { sum = 0 }
/0x000000/ { sum = sum + $2 }
END {print sum}'

Thanks for the Python one-liner above!. It helped me to easy check the used space on my drive. Here is a mixed shell / Python one-liner, that do this - counts used space on the device /dev/sda in megabytes. It took me some time, before I found it out, so, maybe someone finds this useful too.

df -h -B 1M | grep dev/sda | tr -s ' '| cut -d' ' -f3 |python -c "import sys; print sum([int(num) for num in sys.stdin.readlines()])"

or more Python / less shell:

 df -h -B 1M | python -c "import sys; print sum([int(l.split()[2]) for l in sys.stdin.readlines() if '/dev/sda' in l])"

Thanks again!

To sum values in a column you can use GNU datamash. Since the first four lines do not contain values you want to sum up, we remove them with tail +4.

ipcs -mb  | tail +4 | datamash -W sum 7

The -W option sets the field delimiter to (possibly multiple) whitespaces.

If you have specific, multiple columns you want to sum, you can use:

input_command | awk '{s1+=$1;s2+=$2;s3+=$3;s4+=$4;s5+=$5}END{print s1,s2,s3,s4,s5}'

which will work if you want to sum columns 1–5.

Inconceivable how perl wasn't examplified!

See perldoc perlrun for -a (which implies -n). And perldoc perlvar to learn about $. and friends.

$ df |perl -aE'$.<2or$u+=$F[2]}{say"Used: $u"'
Used: 129016836

And if you really want to go crazy:

$ df -h |perl -anE'$|=1;
  BEGIN{%M=(""=>1,k=>1e3,K=>2**10,M=>2**20,G=>2**30,T=>2**40);%D=reverse%M}
  print;
  if($.<2){@V=map length(),/\s*+[^a-z]\S*(?:\s+[a-z]+)*/g;next} # parse header
  ($w=($_==$#V)+length($F[$_])-$V[$_])>0 and do{$V[$_]+=$w;$_<$#V and $V[$_+1]-=$w} for 0..$#F; # optimize column widths
  $S[$_]+=($F[$_]=~/^(\d+(?:[.]\d*)?)([kKMGT])?$/aa?$1*$M{($D||=$2)&&$2}:-Inf)for 0..$#F; # scale numeric values
}{ # show results
  say join("",map+("-"x($V[$_]-1)).($S[$_]<0?"^":"+"),0..$#V);
  $V[$_]+=$V[$_-1]for 1..$#V;
  if($D){for$s(@S){@s=sort{$b<=>$a}grep{$_<$s}keys%D and$s=sprintf"%.1f%s",$s/$s[0],$D{$s[0]}}}
  say sprintf+("%s%*s"x@S),map{((!$p||($_>0 and length($S[$_])>=($w=($V[$_]-$V[$_-1])))?(($q?"\n":(($p=$q=1)&&"")),$V[$_]):("",0+$w)),$S[$_])}grep{$S[$_]!=-Inf}0..$#S;
'