Title sums it up.
$ echo `seq 0 10` `seq 5 15` | sort -n
0 1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 12 13 14 15
Why doesn't this work?
Even if I don't use seq:
echo '0 1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 12 13 14 15' | sort -n
0 1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 12 13 14 15
And even ditching echo directly:
$ echo '0 1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 12 13 14 15' > numbers
$ sort -n numbers
0 1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 12 13 14 15
sort(1) sorts lines. You have to parse whitespace delimited data yourself:
echo `seq 0 10` `seq 5 15` | tr " " "\n" | sort -n