Why is sorting files by access time not working

atimefilesfilesystemsls

I tried to use command
ls --time=atime

it was working in one directory but wasn't working in another directory.
I opened certain files in vim, evince and other applications but after the
command file access times weren't changed.

When I type touch file.txt the access time is changed, but when I type vim file.txt the access time is not changed.

What is wrong here?

Best Answer

With default mounts options, access times are handled in a special way on linux:

relatime – A filesystem mount with this option causes the access time to be updated if they are (before the update has occurred) earlier than the modification time. This significantly cuts down the writes caused by atime updates.

The relatime mount option was made the default option since linux kernel 2.6.30. That is the reason for ls --time=atime not listing what you expect.

Solution: To use strict (legacy) behavior for atime use the strictatime mount option (e.g. in /etc/fstab).

Note: To completely disable atime updates, one can use noatime.

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Linux – Atime value changing only once after file creation

Is it possible that you use the relatime option when mounting? It is supposed to be some middle way between atime and noatime by not causing as much I/O as atime but still not breaking tools that break with noatime.

This is the description out of man 8 mount:

   relatime
   Update  inode  access times relative to modify or change time.  
   Access time is only updated if the previous access time was 
   earlier than the current modify or change time. (Similar to noat‐
   ime, but doesn't break mutt or other applications that need to 
   know if a file has been read since the last time it was modified.)

   Since Linux 2.6.30, the kernel defaults to the behavior provided 
   by this option (unless noatime was  specified), and the 
   strictatime option is required to obtain traditional  semantics. 

   In addition, since Linux 2.6.30, the file's last access time is 
   always  updated  if  it  is more than 1 day old.

Sorting LS Output by Time – Handling Too Many Files

ls -t on its own will list all files in the current directory with that sorting, without ever needing to list them on the command line at all.

If you need the recursion behaviour of find, or to do some other tests on the files, you can have find generate timestamped entries, either through stat or through GNU find's -printf option and sort it. Something like:

find . -type f -printf '%T@ %p\0' | sort -zn

-printf '%T@ %p\0' generates null-separated Unix timestamp (%T@)-filename (%p) pairs. sort -z is also a non-standard GNU extension, which uses null-delimited records to be filename-safe. The sort option is supported in most of the BSDs too, but -printf is GNU-only as far as I know.

You can cut that output back into filenames only, or any other format you like.

Best Answer

Related Solutions

Linux – Atime value changing only once after file creation

Sorting LS Output by Time – Handling Too Many Files

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