sort

POSIX: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sort.html

Sort line wise.

Uses External R-Way merge. This algorithm allows to sort files that are larger than RAM memory.

Sort f1, f2 together line wise:

sort f1 f2

Useful options:

-r: reverse order
-n: numbers
-u: uniq
-t:: set field separator to :
-k5: sort by the Nth field.

Example:
```
sort -k 2,2n -k 4,4hr
```
- sort field 2 (from 2 to 2) numerically
- sort field 4 by human sizes and reverse
From field 2 to 2, numerically, then from 4 to 4, human and reverse
-R: randomize: pseudo reverse of sorting.
-h: sort by human readable file sizes like 1k, 2M, 3G
-f: ignore case
-fs: ignore case and put always upper before lower
-b: ignore leading blanks
-uf: remove duplicates case insensitive
-m: suppose f1 and f2 are already sorted, making sort faster
-c: check if is sorted

Custom line separator

http://stackoverflow.com/questions/2625976/sorting-space-delimited-numbers-with-linux-bash

No direct way apparently, just tr it.

GNU extensions

-V: sort dot separated versions numbers:

[ "$(printf '10.0\n9.10\n9.9\n' | sort -V)" = "$(printf '9.9\n9.10\n10.0\n')" ] || exit 1