05: Further explanation of `sort`

[mjones01]

Currently in 05 sort and sort -n is introduced, however, on this dataset (downloaded from website link on 31 Aug 2016) both work the same, might want to consider explanation for this.

[iglpdc]

Yep, I agree. By default, if you are ordering according to a numeric value you should always use sort -n. In this case, it doesn't matter because the numbers are properly prepended with some whitespace makes sort work as sort -n. But, I agree it's confusing...

[gdevenyi]

Hi, on this dataset, sort and sort -n do not produce the same results,

from https://github.com/swcarpentry/shell-novice/blob/gh-pages/_episodes/04-pipefilter.md:

> cat lengths.txt
  20  cubane.pdb
  12  ethane.pdb
   9  methane.pdb
  30  octane.pdb
  21  pentane.pdb
  15  propane.pdb
 107  total
> sort lengths.txt
 107  total
  12  ethane.pdb
  15  propane.pdb
  20  cubane.pdb
  21  pentane.pdb
  30  octane.pdb
   9  methane.pdb
> sort -n lengths.txt
   9  methane.pdb
  12  ethane.pdb
  15  propane.pdb
  20  cubane.pdb
  21  pentane.pdb
  30  octane.pdb
 107  total

This is on linux with GNU coreutils' version of sort.

Are you using another system?

[iglpdc]

They produce the same result in the Macs (and maybe in Windows).

[shwina]

Can confirm that both commands produce the same result on Macs. Macs don't use GNU sort by default. Maybe we should just recommend using the -n switch to sort numerically if it doesn't work without it (perhaps in a callout?).

[aliceminotto]

Wouldn't it be good to add a note or a comment in the lesson? Last time we had about 1/3 of the people with a red post it to ask why they were getting a different output than the instructor. I realized the pattern mac/linux users after checking on a couple of people. I guess since the instructor likely works on a specific OS s/he may no notice this before the actual carpentry.