Re^6: How to detect if file is in use?

It appears that the links in /proc/*/fd are canonified, i.e. if you open a symlink to foo, then /proc/$$/fd/xx will also point to foo:

$ perl -le 'symlink("foo","bar") o
r die $!; open F, ">bar" or die $!; print readlink("/proc/$$/fd/".file
+no(F))'
/tmp/foo
[download]

Therefore, you can be sure that the paths in the proc filesystem aren't symlinks. Hard links are a harder problem. fuser seems to always get it right, though.

Comment on Re^6: How to detect if file is in use? Download Code

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Re^7: How to detect if file is in use? by Tanktalus (Canon) on Mar 18, 2005 at 02:17 UTC
I thought this was interesting ... so I expanded it just a wee bit: `$ (cd /tmp; perl -e 'symlink("foo","bar") or die $!; open F, ">bar" or + die $!; rename "foo", "blah" or die $!; print readlink("/proc/$$/fd/ +".fileno(F)),$/'; rm blah bar) /tmp/blah` [download] As should be expected(?), it follows renames. And, quite interestingly ... `$ (cd /tmp; perl -e 'symlink("foo","bar") or die $!; open F, ">bar" or + die $!; unlink "foo" or die $!; print readlink("/proc/$$/fd/".fileno +(F)),$/'; rm bar) /tmp/foo (deleted)` [download] Wow. That's cool. Imagine the abuse one could wreak on a poor programmer by creating a file "/tmp/foo $deleted$" :-) I suppose that testing for the file being deleted means actually testing the symlink via stat (e.g., -e).	[reply] [d/l] [select]
Re^7: How to detect if file is in use? by gellyfish (Monsignor) on Mar 18, 2005 at 09:40 UTC
Yes because as mentioned before `fuser` compares the inode and device number of the file in question with those of the files in `/proc/*/fd` and ignores the fact that they are links. /J\	[reply] [d/l] [select]