Re: [PATCH] maintenance: specify explicit stdin for crontab

[Kevin Daudt <me@ikke.info>]

On Tue, Mar 30, 2021 at 08:02:22AM -0400, Derrick Stolee wrote:
> On 3/30/2021 1:41 AM, Martin Ågren wrote:
> > On Mon, 29 Mar 2021 at 23:23, Kevin Daudt <me@ikke.info> wrote:
> >>
> >> There are multiple crontab implementations that require stdin for
> >> editing a crontab to be explicitly specified as '-'.
> 
> Thank you for reporting this, especially with a patch!
> 
> However, I'm not sure about this adding of '-' being something that
> crontab ignores so commonly. My Ubuntu machine reports this:
> 
> $ crontab -e -
> crontab: usage error: no arguments permitted after this option
> usage:  crontab [-u user] file
>         crontab [ -u user ] [ -i ] { -e | -l | -r }
>                 (default operation is replace, per 1003.2)
>         -e      (edit user's crontab)
>         -l      (list user's crontab)
>         -r      (delete user's crontab)
>         -i      (prompt before deleting user's crontab)
> 
> Is there a way we could attempt writing over stdin, notice the
> failure, then retry with the '-' option?

We do not use -e to edit, we run `crontab` and provide the contents to
stdin. `crontab -e` just opens the crontab in the users editor, which
would work with busybox as well, but that's not what's being done here.

> 
> > 
> > [...]
> > 
> >> --- a/t/helper/test-crontab.c
> >> +++ b/t/helper/test-crontab.c
> >> @@ -17,7 +17,7 @@ int cmd__crontab(int argc, const char **argv)
> >>                 if (!from)
> >>                         return 0;
> >>                 to = stdout;
> >> -       } else if (argc == 2) {
> >> +       } else if ((argc == 3 && !strcmp(argv[2], "-")) || argc == 2) {
> >>                 from = stdin;
> >>                 to = fopen(argv[1], "w");
> > 
> > Would it make sense to make this
> > 
> >   } else if (argc == 3 && !strcmp(argv[2], "-")) {
> > 
> > in order to make this test-tool as picky as possible and to only accept
> > the kind of usage we want to (well, need to) use? The tests as they
> > stand would still pass, which I think argues for us not really needing
> > that "argc == 2".
> > 
> > This would be followed by
> > 
> >   } else
> >           return error("unknown arguments");
> > 
> > which wouldn't be super helpful if you forgot the "-", but helpful
> > enough for an internal test-tool, I guess.
> >
> > Speaking of usage and hints, there's "Usage: ..." in a comment at the
> > top of this file. It should probably be updated either way.
> 
> I agree with Martin's review here, too.

Yes, I agree too, was already contemplating that.

> 
> Thanks,
> -Stolee