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Creation date of a file

 
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bob123
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Since: Nov 04, 2010
Posts: 8



PostPosted: Fri Apr 08, 2011 8:10 am    Post subject: Creation date of a file
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Hi,

how I can find the creation date of a file ?

Thanks in advance
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The Natural Philosopher
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Since: Jul 06, 2009
Posts: 196



PostPosted: Fri Apr 08, 2011 8:10 am    Post subject: Re: Creation date of a file [Login to view extended thread Info.]
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bob123 wrote:
> Hi,
>
> how I can find the creation date of a file ?
>
> Thanks in advance
the nearest you will get is the ctime field revealed by stat, I think.
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Richard Kettlewell
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Since: Feb 19, 2005
Posts: 217



PostPosted: Fri Apr 08, 2011 11:10 am    Post subject: Re: Creation date of a file [Login to view extended thread Info.]
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The Natural Philosopher writes:
> bob123 wrote:
>> Hi,
>>
>> how I can find the creation date of a file ?
>>
>> Thanks in advance
> the nearest you will get is the ctime field revealed by stat, I think.

....which is also updated by chmod, chown, rename, unlink, etc.

IOW you can't, on Linux.

--
http://www.greenend.org.uk/rjk/
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The Natural Philosopher
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Since: Jul 06, 2009
Posts: 196



PostPosted: Fri Apr 08, 2011 12:10 pm    Post subject: Re: Creation date of a file [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

Richard Kettlewell wrote:
> The Natural Philosopher writes:
>> bob123 wrote:
>>> Hi,
>>>
>>> how I can find the creation date of a file ?
>>>
>>> Thanks in advance
>> the nearest you will get is the ctime field revealed by stat, I think.
>
> ...which is also updated by chmod, chown, rename, unlink, etc.
>
> IOW you can't, on Linux.
>
I had a nasty feeling that was in fact the case..

But for a normal file that doesn't get subjected to the above tortures,
ctime is as good as it gets, no?.
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Doug Freyburger
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Since: Dec 06, 2010
Posts: 10



PostPosted: Fri Apr 08, 2011 4:10 pm    Post subject: Re: Creation date of a file [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

The Natural Philosopher wrote:
> Richard Kettlewell wrote:
>> The Natural Philosopher writes:
>>> bob123 wrote:
>
>>>> how I can find the creation date of a file ?
>
>>> the nearest you will get is the ctime field revealed by stat, I think.
>>
>> ...which is also updated by chmod, chown, rename, unlink, etc.
>
> I had a nasty feeling that was in fact the case..
>
> But for a normal file that doesn't get subjected to the above tortures,
> ctime is as good as it gets, no?.

Generally mtime beats ctime.

1) There are a lot of backup utilities (tar is the best known) that
just copy the file to backup media. That sets the atime. There are a
lot of backup utilities (cpio is the best known) that save the inode,
copy the file to backup media, then restore the inode. That preserves
the atime but it sets the ctime. Neither strategy effects the mtime.

2) When writing to a file sometimes the ctime is changed sometimes it is
not. If a file is extented at all, end of file marker in the inode is
"c"hanged, whether the list of blocks in the inode structure is changed
or not. This means it happens that ctime is older than mtime but it's
common for both to track. Add in backups and mtime tends to be older.

The UNIX inode structure does not include a create time the way ODS-2 on
VMS did. The best you can get is the oldest of mtime, ctime and atime.
If you have to pick only one, mtime beats ctime for the reasons above.

It's not hard to find all three and compare - Do that.
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Richard Kettlewell
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Since: Feb 19, 2005
Posts: 217



PostPosted: Fri Apr 08, 2011 5:10 pm    Post subject: Re: Creation date of a file [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

Doug Freyburger writes:
> Generally mtime beats ctime.
>
> 1) There are a lot of backup utilities (tar is the best known) that
> just copy the file to backup media. That sets the atime. There are a
> lot of backup utilities (cpio is the best known) that save the inode,
> copy the file to backup media, then restore the inode. That preserves
> the atime but it sets the ctime. Neither strategy effects the mtime.
>
> 2) When writing to a file sometimes the ctime is changed sometimes it is
> not. If a file is extented at all, end of file marker in the inode is
> "c"hanged, whether the list of blocks in the inode structure is changed
> or not. This means it happens that ctime is older than mtime but it's
> common for both to track. Add in backups and mtime tends to be older.

All writes update ctime, at least in ext3. It's nothing to do with
whether the length changes.

See 'man fstat', do the experiment, or look at the kernel source.

--
http://www.greenend.org.uk/rjk/
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