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I have some files on a server with the date several months ago, but they are invisible to find -mtime 7 search.

When I list them with ls -l, they look perfectly normal:

-rw-r--r-- 1 root root    347253 Jun 12 16:26 pedia_main.2010-06-12-04-25-02.sql.gz
-rw-r--r-- 1 root root 490144578 Nov 24 16:26 gsmforum_main.2010-11-24-04-25-02.sql.gz

The top file is invisible to "find . -mtime 1", but the bottom one is visible.

I almost banged my head against the wall trying to understand why. I tried some random things and came across ls --full-time command. And it shows that these two are somehow a little bit different

-rw-r--r-- 1 root root    347253 2010-06-12 16:26:20.000000000 +0400 pedia_main.2010-06-12-04-25-02.sql.gz
-rw-r--r-- 1 root root 490144578 2010-11-24 16:26:12.000000000 +0300 gsmforum_main.2010-11-24-04-25-02.sql.gz

The date seems to be ok. Bit one has +0400 as a timezone, and another one is +0300. How come find fails to find the ones with +0400?

The OS is CentOS 5.5 Final with latest updates, and ls version is (GNU coreutils) 5.97.

Also, the thing is that I don't understand where this "timezone" of the file is stored. The inode does not have any extra attributes to store them it seems. The file system on the server is ext4.

poige
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Vladislav Rastrusny
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    The difference in timezone offset is due to the fact that one date is during Daylight Saving Time for your time zone and the other is not. Since UTC doesn't shift and your time zone does, the offset from UTC changes. The time zone is not stored with the file. The offset is calculated when the directory entry is output. – Dennis Williamson Dec 01 '10 at 14:49

4 Answers4

17

It's possible that the time zone issue is a red herring.

find . -mtime 7

should find files that are exactly seven days old ("seven" meaning between 7.000 and 7.999 days, give or take, and "old" meaning "since last modification"). If you want files that are more than seven days old, which judging by the date on your first file (June 2010) you do, try

find . -mtime +7

I agree with you about the apparent timezone being odd, but I think it's explicable. man stat is clear that a time_t is stored, as Sean R says below. What ls is doing is displaying that as a local time, and it's being kind enough to take account of local daylight-saving conventions when it does so.

My system is the same: file times which happen to fall in Mar-Oct are shown with a +0100 timezone while those which fall in Oct-Mar are shown with a +0000 timezone, not because this is stored in the file system, but because the time zone file tells my system that in June, when I touched the file, I would have done it at a time that I thought was 8am, not it-would-be-7am-if-it-were-winter. ls is kind enough, when displaying times that happen to be in summer, to show them as they would have appeared in summer, that's all.

If you can find any time zones in your ls output that aren't either summer or winter according to your local convention, then I'm wrong - but I can't find any on my system.

MadHatter
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4

With find, -mtime works in 24 hour periods so

-mtime 0 or -mtime -1 mean today
-mtime 3 would mean 3 days old
-mtime +1 means greater than one day old 
-mtime -7 means less than 7 days old
user9517
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  • I know. Actually, I used `mtime 7` variant. But it doesn't work also despite the date is much in the past. – Vladislav Rastrusny Dec 01 '10 at 13:22
  • to get find to show your older file you would need to have a `+` in your time spec e.g `-mtime +7` which will find all files older than 7 days. – user9517 Dec 01 '10 at 15:27
  • This is problem I had understanding: `-mtime +0 means greater than 24 hours ago` `-mtime +1 means greater than 24 hours + one day (48 hours ago)` > find $HOME -mtime 0 Search for files in your home directory which have been modified in the last twenty-four hours. This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. – Tim Lum May 31 '18 at 18:05
2

To explain the time zone portion of it a bit more (the "mtime" discussion is handled by other comments)...

Date and times are stored on files as seconds since midnight January 1, 1970, UTC. Meaning there is no time-zone associated with them. Programs then use the system timezone setting in /etc/timezone, unless overridden by the "TZ" environment variable, to display that time in the local timezone:

chats:/tmp$ touch foo
chats:/tmp$ ls -l foo
-rw-r--r-- 1 jafo jafo 0 Dec  1 06:14 foo
chats:/tmp$ TZ=GMT ls -l foo
-rw-r--r-- 1 jafo jafo 0 Dec  1 13:14 foo
chats:/tmp$

Note in the last line it is showing 1:14 pm, and in the output above it, where I am using my default timezone of US Mountain time (GMT-0700) it is showing 6:14 am. The difference is the second "ls" I set the TZ environment variable to GMT.

You may want to use "stat" to examine all the time/dates associated with files as well.

Peter Mortensen
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Sean Reifschneider
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  • I still don't see, how this allows two different files in the same `ls` listing to have different timezone data in mtime attribute. – Vladislav Rastrusny Dec 01 '10 at 13:27
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    The *FILES* do *NOT*. It is the users who have the timezone data. All times are stored as I mentioned: seconds since Jan 1 1970 midnight. – Sean Reifschneider Dec 01 '10 at 18:57
  • I've got an answer on another forum - different GMTs are due to different file dates. In June it's still +3, in November it becomes +4. So, no magic here also ;) Thanks. – Vladislav Rastrusny Dec 01 '10 at 19:30
1

In addition to the above, I often use the following:

find -mtime -7 -daystart

That tells find to find files that are up to (7 * 24) hours old from the beginning of today.

SmallClanger
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