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infinite while do loop problem

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# 1  
Old 07-16-2009
infinite while do loop problem
hi all,

this is how my scrip looks like
Code:
#!/bin/sh

bindir='/opt/apps/script/bin'
datadir='/opt/apps/script/data'
dir='/opt/apps/script'

while : ; do
     ls -1rt /opt/apps/script/data/check.txt*|tail -1 > /dev/null 2>&1
     if [ $? -eq 0 ] ;then
          chmod +rwx $bindir/dummy2.sh
          lastfile=`ls -1rt /opt/apps/script/data/check.txt*|tail -1` > /dev/null 2>&1
          cp $lastfile $dir/backup/
          cp $lastfile $datadir/IPLIST.txt
     else
         chmod -rwx $bindir/script_check2.sh
         exit 0
     fi
done

Its giving me infinite loop. The check.txt is not in the /opt/apps/script/data/ directory, so I thought I wanted it to do chmod -rwx $bindir/script_check2.sh and exit script straight away.

please help.
Last edited by tententen; 07-16-2009 at 08:57 AM.. Reason: code tags
# 2  
Old 07-16-2009
The loop is infinite since you you used : to evaluate as true which will always be true.
Maybe add a "if -e check.txt"-test instead checking if the file is ls'able and reading it's last line.
Also if you don't want a loop at all, don't use it.
If it is a thing you only want to do once or by cron then no infinite while loop is needed.
If you want to use it like a demon, a permanent process that is running, checking and doing your commands on the files, then stick with the infinite while loop.

Also add CODE-tags to your forum posts in future to enhance readability and to keep formatting like indentition etc. next time. I added CODE-tags to your post so you can see what I mean.
# 3  
Old 07-16-2009
Okay, I need to use the loop because the script are in chained list of process flow, and I execute the script to check if the file is available or not, if it doesnt then exit. I did ls -1rt because I need to process the file from the latest file available, and once its processed on the next flow, another script will remove the latest check.txt(timestamp) until no more available.

Would you kindly please fix my script where need be and repost the code please? I would really appreciate it thank you very much for your prompt support! SmilieSmilie
# 4  
Old 07-16-2009
I have a meeting right now - will have a look into it after the meeting. Maybe someone else does. You are right about the latest file - I misread the ls -ltr, sorry.
# 5  
Old 07-16-2009
Assuming your script is called $bindir/script_check2.sh , changing the execute status of the script you are running will not stop the script.

Quote:
else
chmod -rwx $bindir/script_check2.sh
exit 0
fi
To exit a while loop, use shell command "break".

Code:
else
         break
fi

BTW: There may be logic issues in the script. If a check file does exist, it will copy the file in an infinite loop.
# 6  
Old 07-16-2009
Be aware of the return code of this line, it gives the return code of the tail command:

Code:
ls -1rt /opt/apps/script/data/check.txt*|tail -1 > /dev/null 2>&1

The return code is always 0 in this case. Maybe you can do something like:

Code:
file=`ls -1rt /opt/apps/script/data/check.txt*|tail -1 2>/dev/null`

if [ -z "$file" ]; then
  ...
fi

# 7  
Old 07-16-2009
errmm hmm
Last edited by tententen; 07-22-2009 at 08:32 AM..
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