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

[Derrick Stolee <stolee@gmail.com>]

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?

> 
> [...]
> 
>> --- 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.

Thanks,
-Stolee