Kind of puzzled about timestamps

Bruce Labitt bdlabitt at gmail.com
Thu Mar 4 19:13:41 EST 2021


Good point.  I'll check that.  Logging machine was set to local time EST.
But it does have a wireless link, maybe it set itself internally to UT.
Thanks for the hint.



On Thu, Mar 4, 2021, 7:05 PM Dana Nowell <dananowell at cornerstonesoftware.com>
wrote:

> If I'm reading it correctly, it's a 5 hr difference?  Local vs gmt?
>
>
> On Thu, Mar 4, 2021, 6:43 PM Bruce Labitt <bruce.labitt at myfairpoint.net>
> wrote:
>
>> This is an odd question.  It involves both python and linux.
>>
>> Have a bunch of files in a directory that I'd like like to sort by
>> similar names and in time order.  This isn't particularly difficult in
>> python.  What is puzzling me is the modified timestamp returned by python
>> doesn't match whats reported by the file manager nautilus or even ls.  (ls
>> and nautilus are consistent)
>> $ lsb_release -d Ubuntu 20.04.2 LTS
>> $ nautilus --version  GNOME nautilus 3.36.3
>>
>> $ python3 --version  Python 3.8.5
>>
>> $ ls -lght
>> total 4.7M
>> -rw-r--r-- 1 bruce 209K Feb 26 01:49 20210226_022134_PLD.edf
>> -rw-r--r-- 1 bruce  65K Feb 26 01:49 20210226_022134_SAD.edf
>> -rw-r--r-- 1 bruce 2.4M Feb 26 01:49 20210226_022133_BRP.edf
>> -rw-r--r-- 1 bruce 1.1K Feb 26 00:58 20210225_224134_EVE.edf
>> -rw-r--r-- 1 bruce 1.9M Feb 25 21:18 20210225_224141_BRP.edf
>> -rw-r--r-- 1 bruce 169K Feb 25 21:17 20210225_224142_PLD.edf
>> -rw-r--r-- 1 bruce  53K Feb 25 21:17 20210225_224142_SAD.edf
>>
>> Python3 script
>>
>> #!/usr/bin/env python3
>> import os
>> from datetime import datetime
>>
>> def convert_date(timestamp):
>>   d = datetime.utcfromtimestamp(timestamp)
>>   formatted_date = d.strftime('%d %b %Y  %H:%M:%S')
>>   return formatted_date
>>
>> with os.scandir('feb262021') as entries:
>>   for entry in entries:
>>     if entry.is_file():
>>       info = entry.stat()
>>       print(f'{entry.name}\t Last Modified: {convert_date(info.st_mtime)
>> }' )  # last modification
>>
>> info *(after exit) contains*: os.stat_result(st_mode=33188,
>> st_ino=34477637, st_dev=66306, st_nlink=1, st_uid=1000, st_gid=1000,
>> st_size=213416, st_atime=1614379184, st_mtime=1614322176,
>> st_ctime=1614379184)
>>
>> Running the script results in:
>>
>> 20210226_022133_BRP.edf     Last Modified: 26 Feb 2021  06:49:34
>> 20210225_224141_BRP.edf     Last Modified: 26 Feb 2021  02:18:42
>> 20210225_224142_PLD.edf     Last Modified: 26 Feb 2021  02:17:44
>> 20210225_224142_SAD.edf     Last Modified: 26 Feb 2021  02:17:44
>> 20210225_224134_EVE.edf     Last Modified: 26 Feb 2021  05:58:26
>> 20210226_022134_SAD.edf     Last Modified: 26 Feb 2021  06:49:36
>> 20210226_022134_PLD.edf     Last Modified: 26 Feb 2021  06:49:36
>>
>> Actually, what is returned by my script is at least sensible, given that
>> 20210225_224141_BRP.edf started on Feb 25th and ended recording at
>> 2:17am on Feb 26th.  I know this because I can see the data on a separate
>> program.  20210226_022133_BRP.edf started on Feb 26th at around 2:21am
>> and terminated at 6:49am.  BRP files are written to continuously at a 25 Hz
>> rate all evening.  What makes no sense whatsoever is what *ls* is
>> reporting.
>>
>> Do *ls* and python3 use different definitions of "last modified"?
>>
>> Guess I can keep going, but I really was surprised at the difference
>> between methods.  Default for ls is "last modified", at least as reported
>> by man.  ls's last modified just isn't correct, at least on Ubuntu 20.04.2
>>
>> Is this a quirk?  Am I doing something wrong?  Some kind of voodoo
>> definition of "last modified"?  What does Linux say "last modified" really
>> means?
>>
>> FWIW, I am coming up to speed on processing these edf files to help out
>> on an open source project.  Been working on some data analysis tools.  As
>> an aside, biological data is very messy.  It's been a treat to work on this
>> as it's forced me to dust off the mental cobwebs and work on a problem that
>> can help a lot of people.
>>
>>
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