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

On Tue, Mar 30, 2021 at 08:02:22AM -0400, Derrick Stolee wrote:

On 3/30/2021 1:41 AM, Martin Ågren wrote:

quoted

On Mon, 29 Mar 2021 at 23:23, Kevin Daudt [off-list ref] wrote:

quoted

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.

quoted

[...]

quoted

--- 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