gnus-agent-fetch in batch mode in a cron job

gnus-agent-fetch in batch mode in a cron job

[Julien Cubizolles]

The subject says it all. I'm fetching news through emacs in batch mode
in a cron job but I can't figure out how to get the possible errors
through the mails sent by cron.

In batch mode emacs output everything that should go to the *Messages*
buffer to stderr so cron sends an email each time the job is run, even
without any error. I don't want to receive an email when there is no
problem. Is there a way to get emacs to send only the error messages to
stderr ?

Julien.


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Re: gnus-agent-fetch in batch mode in a cron job

[W. Greenhouse]

Hi Julien,

Julien Cubizolles <j.cubizolles@free.fr> writes:

> The subject says it all. I'm fetching news through emacs in batch mode
> in a cron job but I can't figure out how to get the possible errors
> through the mails sent by cron.
>
> In batch mode emacs output everything that should go to the *Messages*
> buffer to stderr so cron sends an email each time the job is run, even
> without any error. I don't want to receive an email when there is no
> problem. Is there a way to get emacs to send only the error messages to
> stderr ?
>
> Julien.

Yes, this should be a matter of shell redirection.  Cron actually sends
both stdout and stderr to email, so if you only want stderr, then you
should redirect stdout to /dev/null.  There isn't a -quiet option or
similar for Emacs in batch mode, so it's all up to the shell.

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Re: gnus-agent-fetch in batch mode in a cron job

[Julien Cubizolles]

wgreenhouse@riseup.net (W. Greenhouse)
writes:

> Hi Julien,
>
> Julien Cubizolles <j.cubizolles@free.fr> writes:
>
>> The subject says it all. I'm fetching news through emacs in batch mode
>> in a cron job but I can't figure out how to get the possible errors
>> through the mails sent by cron.
>>
>> In batch mode emacs output everything that should go to the *Messages*
>> buffer to stderr so cron sends an email each time the job is run, even
>> without any error. I don't want to receive an email when there is no
>> problem. Is there a way to get emacs to send only the error messages to
>> stderr ?
>>
>> Julien.
>
> Yes, this should be a matter of shell redirection.  Cron actually sends
> both stdout and stderr to email, so if you only want stderr, then you
> should redirect stdout to /dev/null.  There isn't a -quiet option or
> similar for Emacs in batch mode, so it's all up to the shell.

From what I understand Emacs outputs the whole *Messages* buffer to
stdout. So there is nothing the shell can do to sort error messages from
information messages. Is that right ?


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Re: gnus-agent-fetch in batch mode in a cron job

[W. Greenhouse]

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Hi Julien,

Julien Cubizolles <j.cubizolles-GANU6spQydw@public.gmane.org> writes:

> From what I understand Emacs outputs the whole *Messages* buffer to
> stdout. So there is nothing the shell can do to sort error messages from
> information messages. Is that right ?

Hrm, you're not quite correct, but I'm not sure it actually matters.
From (info "(emacs) Initial Options"):

> `-batch'
> `--batch'
>      Run Emacs in "batch mode".  Batch mode is used for running
>      programs written in Emacs Lisp from shell scripts, makefiles, and
>      so on.  To invoke a Lisp program, use the `-batch' option in
>      conjunction with one or more of `-l', `-f' or `--eval' (*note
>      Action Arguments::).  *Note Command Example::, for an example.

>      In batch mode, Emacs does not display the text being edited, and
>      the standard terminal interrupt characters such as `C-z' and `C-c'
>      have their usual effect.  Emacs functions that normally print a
>      message in the echo area will print to either the standard output
>      stream (`stdout') or the standard error stream (`stderr') instead.
>      (To be precise, functions like `prin1', `princ' and `print' print
>      to `stdout', while `message' and `error' print to `stderr'.)
>      Functions that normally read keyboard input from the minibuffer
>      take their input from the terminal's standard input stream
>      (`stdin') instead.

etc.

So which file descriptor emacs --batch sends printed output to does
actually depend on the function being called.  And looking at the source
of gnus-agent, it does look like functions like `signal' and `error' are
consistently used as they should be, for actual network errors--which is
good.  However, `message' is also used frequently, e.g. for the
"Checking new news..." in `gnus-group-check-new-news.'  So it's not
guaranteed that stderr will only contain errors.  So, you might actually
be better off either redirecting all output to /dev/null (as the example
in (info "(gnus) Batching Agents") does), or else redirect to a log
file.

--
Regards,
WGG

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Re: gnus-agent-fetch in batch mode in a cron job

[Lars Magne Ingebrigtsen]

Julien Cubizolles <j.cubizolles@free.fr> writes:

>>From what I understand Emacs outputs the whole *Messages* buffer to
> stdout. So there is nothing the shell can do to sort error messages from
> information messages. Is that right ?

I think that's correct.

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