awk で気軽に集計 ref: http://qiita.com/kitsuyui/items/3647bd5b8a5b3e858d3c

file1.txt

$ awk '{s += $1} END {print s}' < sample-1.txt
18

file3.txt

$ awk '{a += $1; b += $2} END {print a, b}' < sample-2.txt
10 26

file5.txt

$ sort -n < sample-3.txt | uniq -c
   7 a
   3 b
   1 c

file6.txt

$ sort -n < sample-3.txt | uniq -c | awk '{a+=$1; print $2, $1} END {print "計”, a}'
a 7
b 3
c 1
計 11

sample-1.txt

3
4
5
6

sample-2.txt

1 5
2 6
3 7
4 8

sample-3.txt

a
a
a
a
a
a
a
b
b
b
c