How to determine if a file is open 1

[Xitron]

AIX 4.3.3.0-10 - Oracle 8.1.7.4

I'm trying to write a bourne script to periodically backup the Oracle archive redo files to a different server just to cover my arse. However, I don't want to make the mistake of copying a file that is in the process of being written. Is there a simple AIX command-line method for determining if a file is open, and therefore should not be copied?

I'm thinking of something along the lines of:

for fil in `ls archive*`
do
<test to see if file is open, and if so, set a variable>
if <variable in previous step not set>
cp $fil backup-location
else
mail -s &quot;$fil was open and was not copied&quot; me@my.com
fi
done

Ideas?

Thanks,

Unca Xitron

 

[nwardez]

Hi,

fuser <file_name> gives you PID that access a file (man fuser for more details).

 

[Xitron]

Hi nwardez. First, thank you for replying. fuser is a great option, but either it is not doing what we'd hoped, or I'm not interpreting the output correctly.

Example:

On one screen I do the following:

# vi myfile.sh

On a second screen I then run the following command, and get the following:

# fuser myfile.sh; echo $?
myfile:
0
#

And if I `touch` a new file, for the sole purpose of testing:

# touch crapmonkey
# fuser crapmonkey; echo $?
crapmonkey:
0
#

So in the case of a file that is definitely open for editing, vs. a file that has been newly created and which is NOT open, the output and the $? are identical. I don't have access to the AIX man pages (why oh why, but that's a different thread altogether), so I peeked at the Linux man page for same. Very different. In fact, when I intentionally err in the AIX version, the only options I am offered are:

Usage: fuser [-cdfkuVx] File ...

Not being lazy here, folks. I just don't have access to the docs I need. I'll post THAT thread in a minute.

Any clarifications on the fuser idea, or any other ideas?

Unca Xitron

 

[nwardez]

Yes, my answer was a bit short...

fuser shows you the PID of the process that access a file. It returns 0 if it runs successfully. That's why you get 0 with &quot;echo $?&quot; after fuser. But if you try:

1. First screen
touch foo
tail -f foo
2. Second screen
fuser foo

2nd screen will give you a process number you can &quot;ps|grep&quot; to check it is. Hope it helps.

By the way, did you check your MANPATH environment variable for accessing man pages ?

 

[Xitron]

Thanks, nwardez. I guess I figured that having a file open with vi would be sufficient for having it considered &quot;open&quot;. So would I be correct in guessing that a file that is being written to would show up with a PID that I could grep for as a test for being &quot;open&quot;?

As for the man pages, I found several excellent posts (thanks aixqueen!) regarding the man pages. Looks like it is time for me to dig out the CDs. :-/

Thanks again,

Unca Xitron

 

[aixmurderer]

Try something like this in your script:

CNT=`fuser $fil 2>&1 | awk '$2 != &quot;&quot; { print $1 }' | cut -d: -f1|wc -l`
if [ $CNT -eq 0 ];then
cp blabla
else
mail blabla
fi
IBM Certified Confused - MQSeries
IBM Certified Flabbergasted - AIX 5 pSeries System Administration

 

[Xitron]

Thanks aixmurderer! Since I've never taken the time to learn awk (BAD sysadmin!! Bad!!!), this was my approach...

for fil in $ARCHDIR/arch*
do
INUSE=`fuser $fil | cut -d: -f2` # Get a PID if in use

if [ $INUSE > &quot;&quot; ] # Is file being written to?
then
echo &quot;$fil in use... not backed up&quot; >> $LOGFILE #skipit
else
grep $fil $DONELIST # Has it already been backed up?
ISDONE=$?

if [ $ISDONE -ne 0 ]
then
echo $fil >> $BACKLIST # Add to list to back up
fi

fi

done


Clumsy, and not as elegant as many scripters on this site could have done, but it works. I'm studying perl and awk at this time, so my next attempt should be a lot cleaner.

Thanks again, all. Great place this website!

Unca Xitron

 

[mrtex]

You don't have to install anything to get to the AIX docs. They are available online. Try going to :

http://techsupport.services.ibm.com/server/library

and then scroll down. You should see links for 4.3, 5.1 and 5.2 docs.

 

[Xitron]

Perfect, mrtex! Thank you!!

Unca Xitron

 

[mgshn]

Thought I would jump in and explain the confusion about using vi to edit a file and fuser to see if the file being edited is open. The problem is that vi does not keep the file open during the editing session. It creates a copy of the file and uses that for the updates. When you leave vi and save changes it overwrites the original file.

 

[Xitron]

mgshn: thanks for clearing that up for me. Much appreciated!