G'day Mark,

The directory is a file. You can view it in an editor. When you open a file for writing, even if you don't write anything, the information in the directory file will change and, accordingly, so will the timestamp. You can see this for yourself at the command line (i.e. without using perl) - here's a sample run: 

ken@ganymede: ~/tmp
$ ls -al check_dir_touch
ls: check_dir_touch: No such file or directory
ken@ganymede: ~/tmp
$ mkdir check_dir_touch
ken@ganymede: ~/tmp
$ ls -al check_dir_touch
total 0
drwxr-xr-x    2 ken  staff    68  5 Feb 20:12 .
drwxr-xr-x  211 ken  staff  7174  5 Feb 20:12 ..
ken@ganymede: ~/tmp
$ view check_dir_touch
---------------------
Editor window shows various info with no files listed
(exit editor without attempting to save anything)
---------------------
ken@ganymede: ~/tmp
$ > check_dir_touch/fred
ken@ganymede: ~/tmp
$ ls -al check_dir_touch
total 0
drwxr-xr-x    3 ken  staff   102  5 Feb 20:19 .
drwxr-xr-x  210 ken  staff  7140  5 Feb 20:18 ..
-rw-r--r--    1 ken  staff     0  5 Feb 20:19 fred
ken@ganymede: ~/tmp
$ view check_dir_touch
---------------------
Editor window now shows "fred"
(exit editor without attempting to save anything)
---------------------

[download]

I agree with vinoth.ree's comment about using the 3-argument form of open; however, that won't change the behaviour of the underlying operating system.

-- Ken

In reply to Re: why does open ">..." sometimes touches the directory? by kcott
in thread why does open ">..." sometimes touches the directory? by Mark_Galeck

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