On Thu, Mar 30, 2017 at 03:25:43PM -0300, Daniel Ferreira (theiostream) wrote:
> On Thu, Mar 30, 2017 at 4:46 AM, Michael Haggerty <mhag...@alum.mit.edu>
> wrote:
> > Is there a special reason to write the date to the file as opposed to, say
> >
> > touch dir/b
> >
> > ? (Some people use `: >dir/b` for this purpose, though I've never found
> > out why.) If you write the date to the file, the reader will be
> > distracted unnecessarily wondering whether the contents are important to
> > the test.
> >
>
> There's no reason. They will be `touch`ed instead of written in a next
> version.
>
> `:` is a bash builtin that that returns an exit code of zero and
> produces no output. On my Mac at least:
>
> bash-3.2$ type :
> : is a shell builtin
> bash-3.2$ type touch
> touch is /usr/bin/touch
>
> I suppose there are reasons to try to keep the most of a shell
> script's logic within the shell itself, without involving external
> binaries.
I think we actually prefer just:
>dir/b
in our tests. The advantages over touch are:
1. It is clear that the output will be empty afterwards (whereas with
touch, it might just update the timestamp on an existing file).
2. It's faster, since it doesn't require an extra process.
It's equivalent to ": >dir/b". I think you'll find all three forms in
our test suite, but ">dir/b" is the most common.
-Peff
