Re: fractional file timestamps in tramp-adb

[Michael Albinus <michael.albinus@gmx.de>]

Paul Eggert <eggert@cs.ucla.edu> writes:

Hi Paul,

> Interesting. Does it work without the ".318491822" but keep the "Z"?

Yes.

--8<---------------cut here---------------start------------->8---
$ touch -d 2019-02-14T18:23:17.318491822 /sdcard/tmp/foo            
touch: '/sdcard/tmp/foo': Operation not permitted
--8<---------------cut here---------------end--------------->8---

> How about if you replace ".31849182" with ".000000000" while keeping
> the "Z"?

Doesn't work.

--8<---------------cut here---------------start------------->8---
 $ touch -d 2019-02-14T18:23:17.000000000Z /sdcard/tmp/foo         
touch: bad '2019-02-14T18:23:17.000000000': Value too large for defined data type
--8<---------------cut here---------------end--------------->8---

> Can you strace the 'touch' and see what system calls are failing and
> what their arguments are?

There's no strace on my Galaxy.

In older Android versions, most of the coreutils were implemented via
busybox. This has been replaced by toybox:

--8<---------------cut here---------------start------------->8---
$ which touch
/system/bin/touch
$ ls -l /system/bin/touch
lrwxrwxrwx 1 root root 6 2016-03-25 17:04 /system/bin/touch -> toybox
$ toybox --version                                              
0.7.0--android
--8<---------------cut here---------------end--------------->8---

See also <https://lwn.net/Articles/629362/>. tramp-adb.el has already
some few checks for toybox, but not systematically. I suspect we need to
do it better, due to the differences in command parameters, and their
output.

I'm afraid, I'm not an experienced Android developer (tramp-adb.el was
written by somebody else). Any help appreciated!

Best regards, Michael.