Thanks Eric and Bob. I had sorted the files before calling comm, but I think the problem is that I sorted them as numeric:

sort -n test1 -o test1

When I removed the "-n", which is equivalent to what Bob has done, comm worked like a charm.

Sorry for rushing to file this as bug.

Cheers,

Ali

On Wed, Jan 7, 2015 at 5:59 PM, Bob Proulx <bob@proulx.com> wrote:

Eric Blake wrote:
> Ali Khanafer wrote:
> > I tried comm on test1.txt and test2.txt. The output I got is in
> > comm-test.txt. Comm found 11 common lines and missed 6 other lines.
> >
> > Could you please explain why this is happening?
>
> Using a newer version of coreutils would tell you why:
> ...
> Proper use of comm requires that you pre-sort both input files. As
> such, this is not a bug in comm, so I'm closing this bug. However, feel
> free to add further comments or questions.

If you are using bash then a bash specific feature is useful. You can
sort them on the fly.

comm <(sort test1) <(sort test2)

Or perhaps forcing a sort locale.

env LC_ALL=C comm <(sort test1) <(sort test2)

I included LC_ALL=C to force a specific sort order which may or may
not be appropriate for all of your use cases.

Bob