How to know if data is being accessed

[Theresa Patrie]

Hi,
I have a script that runs periodically and changes permissions on new data that shows up in a certain directory. I find new data by comparing the output from a previous "ls" with the output from a new "ls". People will be continuously moving data into this directory. I was going to run my script periodically using cron, but how can I be sure that the new data I see using "ls" has completed its move and is not still in the process of being moved??
Thanks,
Theresa
P.S. I will be on Tuesday but look forward to reading your responses on Wednesday! Thanks!!

[Sridhar Bhaskarla]

Hi,

Oneway I would do is to use fuser command. If you use fuser against a file that is being accessed, it will print out the pid of the process. So, fuser returns anything, then you would skip copying that file or wait until it is done. You can accomplish it using a while statement with a sleep in it.

-Sri

[Robert-Jan Goossens]

Hi,

An other way is using losf.
take a look at the man page.

http://hpux.connect.org.uk/hppd/hpux/Sysadmin/lsof-4.64/

Hope it helps,

Robert-Jan.

[A. Clay Stephenson · Accepted solution]

You could use a find -newer against a reference file but here's my solution:

AGE=300
ls | while read FNAME
do
fileage.pl -m -s ${AGE} ${FNAME}
STAT=${?}
if [[ ${STAT} -eq 0 ]]
then
echo "${FNAME} has not been modified in ${AGE} seconds."
echo "It is safe to copy."
fi
done

Fileage.pl returns 0 if a file has not been modified in a given period; 1 if it has, and > 1 on error.


Invoke as fileage.pl -u for full usage.

[James R. Ferguson]

Hi:

A note of caution: Changing the name, the permissions or the ownership of a file or moving it from one directory to another updates the inode change timestamp as divulged by 'ls -lc'. Beware that 'fbackup' (if you use it) will also change this when it restores the lastaccess timestamp (ls -lu) of a file it copies.

Regards!

...JRF...

[Theresa Patrie]

Hi All,
Thanks for your responses.

I didn't try it, but I don't know if fuser would work if people were writing to this file/directory via nfs. I did, however, use the while statement with a sleep in it. Instead of fuser, I used Clay's suggestion of "find -newer my_touchfile" for a quick and dirty solution. It works great. The other suggestions may be better, but since I needed this done by this afternoon, I didn't have time to download lsof or to get the perl script working.
Thanks again!
Theresa