Need while loop which runs after it finds file.

Sha_unix · 10-13-2011, 06:38 AM

Hi,

I have one cron which runs at 5AM. the script is below.

cron
====
00 5 * * 2-6 /usr/home/progress/bin/stage_5b.sh

script
======
SCRIPTDIR=/emc/reale/apps/pseudo/mss/src/
DLC=/usr/dlc
export DLC
PF=$SCRIPTDIR/stage5.pf

$DLC/bin/mbpro -pf $PF -p $SCRIPTDIR/stage5/ncre-stg5.p

I want to make this run only if it finds prolog.log file in path /stage5_dp04/dump. below loop is not ending. Can anybody help.

Modified script
================
SCRIPTDIR=/emc/reale/apps/pseudo/mss/src/
DLC=/usr/dlc
export DLC
PF=$SCRIPTDIR/stage5.pf

cd /stage5_dp04/dump
while [ -f /stage5_dp04/dump/prolog.log ]
do
$DLC/bin/mbpro -pf $PF -p $SCRIPTDIR/stage5/ncre-stg5.p
exit
done

colucix · 10-13-2011, 06:54 AM

If you put the exit statement inside the while loop, it exits after the first iteration, hence you don't really need a loop: an if/then construct should be enough. If you don't see the loop terminates after a while, maybe its due to a long execution time of the mbpro command (or it sticks for some reason).

tronayne · 10-13-2011, 07:19 AM

Adding to what colucix says, you don't need a loop:

Code:

if [ -f /stage5_dp04/dump/prolog.log ]
then
     $DLC/bin/mbpro -pf $PF -p $SCRIPTDIR/stage5/ncre-stg5.p
fi

You could throw in an else to simply say, "The file does not exist" or something but that's a little overkill.

Hope this helps some.

Sha_unix · 10-13-2011, 08:26 AM

Will it try again if it doesnt find the prolog.log file in path. Coz the timing is 5AM, the file might get generated till 8AM (depends on some other process). So this loop has to try again and again and when found the file prolog.log it has to run this.?

rn_ · 10-13-2011, 09:12 AM

That's not a good idea; what if your file doesn't show up at all; you will have another script start up at 5am the next day, and more after that. You will then need to ensure that only one script starts up at a time.

Sha_unix · 10-13-2011, 09:19 AM

It will show up.. because this script runs mon to sat and prolog.log will showup anytime after 3am but have to make sure after prolog.log gets created our 5am script has to run. Here some time instead of 3am prolog.log file gets genereated at 6am. So if i check this condition and run my 5am script then it will run without a hitch. About another script running at that time doesnt matter here. Please advise. Can the above "if" condition full fills my need.

rn_ · 10-13-2011, 09:30 AM

ok, if you're sure it will show up...

no, the "if" is not sufficient; you can change your while loop like so:

Code:

while [ ! -f /stage5_dp04/dump/prolog.log ]
do
   # wait for file to show up
   sleep 10
done

# out of loop ==> we have the file
$DLC/bin/mbpro -pf $PF -p $SCRIPTDIR/stage5/ncre-stg5.p

tronayne · 10-13-2011, 09:40 AM

OK, as you say, your /stage5_dp04/dump/prolog.log file may not be there at 0500.

So, do a loop

Code:

while true
do
     # is the file there?
     if [ -f /stage5_dp04/dump/prolog.log ]
     then
          # yup, it is, do our thing
          $DLC/bin/mbpro -pf $PF -p $SCRIPTDIR/stage5/ncre-stg5.p
          # all done, get outta here
          break
     fi
     # nope, ain't there; sleep for a half hour
     sleep 30m
done
# now that we've done our thing, let's get rid of that file
rm /stage5_dp04/dump/prolog.log

Note that your version of sleep may not like the m (minutes) suffix; in that case just multiple whatever number of minutes you want to delay by 60 and use that value -- check your manual page for sleep.

Hope this helps some.

Sha_unix · 10-13-2011, 09:41 AM

Thank a lot. i will check and let you know.