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Top Forums UNIX for Advanced & Expert Users tar: how to preserve atime? (also on extracted version, not just original) Post 302268424 by frankie06 on Monday 15th of December 2008 05:44:45 PM
Old 12-15-2008
Quote:
Originally Posted by drl
[...] on the source side, not on the target side. In other words, tar obtains the inode times, reads the file into the accumulation of the output file, then resets the inode times to the original.
Yes drl you are correct. But if an archiving utility like tar includes the ability to carefully restore the original's atime (which requires extra work, i.e. modifying the inode after the file is read), it would be bizarre if the programmers didn't also include the ability to set the extracted copy's atime (which requires absolutely no extra work, because tar always sets the extracted copy's time correctly, and assuming it also sets the atime to something, it is no extra work to set it to the correct value).

Quote:
Originally Posted by drl
Some filesystems are set not to even record the access times, since it is often of limited value and causes disk activity.
Correct. And even if I tar files from such a filesystem (which hence always have an atime long in the past), the atime of the extracted copy is the current time. And also, even if I tar files and *extract* them onto a filesystem that does not record the atime (mount option noatime), the atime is set to the extraction time.

Quote:
Originally Posted by drl
If my supposition is correct, then one could use touch to reset the access times on the target -- tedious, but doable.
But how? Presumably they are stored in the tar archive, but where? And if I wanted a tool that reads stuff from a tar archive, the tool "tar" would be my choice :-)

We are talking about 10000 to 100000 files here. Possibly there are scripts that store and later reset the atimes, but I don't know of any.
 

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SENDFILES(1)							     [nmh-1.5]							      SENDFILES(1)

NAME
sendfiles - send multiple files via a MIME message SYNOPSIS
sendfiles [delay] mailpath subject file1 [file2 ...] DESCRIPTION
The shell script sendfiles, is used to send a collection of files and directories via electronic mail. sendfiles mailpath "subject" files ... sendfiles will archive the files and directories you name with the tar command, and then mail the compressed archive to the "mailpath" with the given "subject". The archive will be automatically split up into as many messages as necessary in order to get past most mailers. Sometimes you want sendfiles to pause after posting a partial message. This is usually the case when you are running sendmail and expect to generate a lot of partial messages. If the first argument given to sendfiles starts with a dash, then it is interpreted as the number of seconds to pause in between postings, e.g., sendfiles -30 mailpath "subject" files ... will pause 30 seconds in between each posting. Extracting the Received Files When these messages are received, invoke mhstore once for the list of messages. The default is for mhstore to store the combined parts as a new message in the current folder, although this can be changed using storage formatting strings. You can then use mhlist to find out what's inside; possibly followed by mhstore again to write the archive to a file where you can subsequently uncompress and untar it. For instance: % mhlist 5-8 msg part type/subtype size description 5 message/partial 47K part 1 of 4 6 message/partial 47K part 2 of 4 7 message/partial 47K part 3 of 4 8 message/partial 18K part 4 of 4 % mhstore 5-8 reassembling partials 5,6,7,8 to folder inbox as message 9 % mhlist -verbose 9 msg part type/subtype size description 9 application/octet-stream 118K (extract with uncompress | tar xvpf -) type=tar conversions=compress % mhstore 9 % uncompress < 9.tar.Z | tar xvpf - Alternately, by using the -auto switch, mhstore will automatically do the extraction for you: % mhlist 5-8 msg part type/subtype size description 5 message/partial 47K part 1 of 4 6 message/partial 47K part 2 of 4 7 message/partial 47K part 3 of 4 8 message/partial 18K part 4 of 4 % mhstore 5-8 reassembling partials 5,6,7,8 to folder inbox as message 9 % mhlist -verbose 9 msg part type/subtype size description 9 application/octet-stream 118K (extract with uncompress | tar xvpf -) type=tar conversions=compress % mhstore -auto 9 -- tar listing appears here as files are extracted As the second tar listing is generated, the files are extracted. A prudent user will never put -auto in the .mh_profile file. The correct procedure is to first use mhlist to find out what will be extracted. Then mhstore can be invoked with -auto to perform the extraction. FILES
$HOME/.mh_profile The user profile PROFILE COMPONENTS
Path: To determine the user's nmh directory Current-Folder: To find the default current folder SEE ALSO
mhbuild(1), mhlist(1), mhshow(1), mhstore(1). Proposed Standard for Message Encapsulation (RFC-934) DEFAULTS
`-noverbose' CONTEXT
None MH.6.8 11 June 2012 SENDFILES(1)
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