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How to have my ksh script pause, until something appears in the logs.?

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Top Forums Shell Programming and Scripting How to have my ksh script pause, until something appears in the logs.?
# 8  
Old 04-11-2013
Would this work:

The first time, check if "DONE" already exists in the log file, using grep -n and tail -n 1 to find the last line number that "DONE" occurs on.

Then use the while loop, sleeping every ten seconds, but tail the log file each time you look, instead of looking at entire log file. That way, you ignore the previous "DONE" lines at the top of the log file that were already there,
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chatguy
# 9  
Old 04-11-2013
Are there no timestamps in this log file?

Or do as you suggested and tail the file. Pipe the stream into code that exits when it matches (grep -q). Worst case, tail will linger until the next time it tries to write (when SIGPIPE will kill it).

Regards,
Alister
Last edited by alister; 04-11-2013 at 05:23 PM..
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chatguy
# 10  
Old 04-11-2013
is it necessary to key off of the "DONE!" or could you somehow have the script check the status of the software under test? maybe running some sort of pre-existing status command or check the system's process list if the readiness of the SUT can be determined that way. (the check could be in a loop that would terminate as soon as it pro-actively determined the "MYSQL DB has bound to the RMI/Software" - if that is possible w/o having to monitor a log for status)
just trying to think of other possible options that might be cleaner for you...
biker
www.LiveFireLabs.com
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chatguy
# 11  
Old 04-12-2013
Replies to Hanson, Biker & Alister & more info on how to solve...
Hi Hanson:

Hm, I think you're on to something. I'll admit, I'm not sure how to "tail in the background" for every 10-seconds, if that is what you mean. (As you can tell, I'm probably somewhere between a novice and intermediate KSH scripter)

But your grep -n idea got me thinking:

Perhaps one way of scripting this is: (?)

1) Shutdown software ("cControl stop")
2) grep -n for DONE! (using awk?, record the "latest" line number that DONE! was found on, or record "0" if not found.)
3) Startup software ("cControl start")
4) In a while loop, every 10 seconds, grep -n for DONE!
4b) Break while loop (somehow?) if grep -n finds a "LATER" line number than what was recorded in step 2 above. <-- Hm, not sure how to do this...but it sounds possible?

Hi Biker:

Very good point that I wish I would have thought of in the design phase! Unfortuanately it's too late to add to the design (as much as it would make things a lot easier), the only way it could be determined though, is with the logs Smilie

Hi Alister:

Yes! There actually are timestamps. This was my first chain of thought, but as I work on this system late (which is also 5 hours ahead in GMT), it's likely I will hit the 00:00:00 midnight hour mid-way through...so I'm not quite sure how to attack it from that angle. Here's a snippet of those logs:
Code:
Apr 11 19:19:39 localhost APP.ph1[16435]: [local4.info] INFO creating Location
Apr 11 19:22:31 localhost APP.ph1[16435]: [local4.info] INFO creating LocDef
Apr 11 19:23:16 localhost APP.ph1[16435]: [local4.info] INFO DONE!
Apr 11 19:30:00 localhost APL.ph0[3102]: [local4.info] INFO APL Heartbeat 2106
Apr 11 19:30:00 localhost APP.ph0[3105]: [local4.info] INFO APP Heartbeat 4074
Apr 11 19:34:40 localhost APP.ph1[16435]: [local4.info] INFO New thread pool of size:3
Apr 11 19:34:41 localhost APP.ph1[16435]: [local4.info] INFO Starting Iteration 1
Apr 11 19:34:43 localhost APP.ph1[16435]: [local4.info] INFO Iteration 1, all tasks finished
Apr 11 19:34:43 localhost APP.ph1[16435]: [local4.info] INFO Running command:/APP/createTar.sh ph1 
Apr 11 19:37:54 localhost APP.ph1[16435]: [local4.info] INFO creating Server
Apr 11 19:41:49 localhost APP.ph1[16435]: [local4.info] INFO creating Site
Apr 11 19:42:05 localhost APP.ph1[16435]: [local4.info] INFO creating Location
Apr 11 19:42:22 localhost APP.ph1[16435]: [local4.info] INFO creating LocDef
Apr 11 19:44:23 localhost APP.ph1[16435]: [local4.info] INFO DONE!

If you know of any way of attacking it from that angle, that would certainly help as well!


ps: Thank you all for your help so far! Definitely appreciated!

CG
Last edited by Franklin52; 04-16-2013 at 03:08 AM.. Reason: Please use code tags for code and data samples
# 12  
Old 04-12-2013
one thing i did for a tool i wrote a year or two back was to use the epoch value (seconds since 1970) for date/timestamp comparisons if that's the concern

biker
LiveFire Labs: Online UNIX Training with Hands-on Internet Lab
# 13  
Old 04-12-2013
Quote:
1) Shutdown software ("cControl stop")
2) grep -n for DONE! (using awk?, record the "latest"
line number that DONE! was found on, or record "0" if not found.)
3) Startup software ("cControl start")
4) In a while loop, every 10 seconds, grep -n for DONE!
4b) Break while loop (somehow?) if grep -n finds a "LATER"
line number than what was recorded in step 2 above.
<-- Hm, not sure how to do this...but it sounds possible?
Yes, this is exactly what I'm suggesting. Here is working code, using sed as a better way to get the part of log file to test:
Code:
LAST_LINE_WITH_DONE=`grep -n DONE log | tail -n 1 | cut -d : -f 1`
if [ -z "$LAST_LINE_WITH_DONE" ]; then
  LINE_1_TO_TEST=`wc -l < log`
else
  LINE_1_TO_TEST=`expr $LAST_LINE_WITH_DONE + 1`
fi

while sleep 10; do
  sed -n "$LINE_1_TO_TEST,$ p" log > lines-to-test.txt
  grep -q DONE lines-to-test.txt
  if [ $? -eq 0 ]; then
    echo "Found DONE in newly created section of log"
    # Take additional actions
    # Perhaps break out of look
  fi
done

This User Gave Thanks to hanson44 For This Post:
chatguy
# 14  
Old 04-12-2013
SOLVED
Hansen,

You are a genius! At the same time, I never thought it was this easy to do this! Thank you and everyone who chimed in!!

ps: If the word DONE was not previously in the file, the variable is NULL. Turns out this is just fine, since I can compare null with 1, if the first DONE is added.

Here is the modified code I used:
Code:
LOGFILE="/tmp/tmp.log"

LAST_LINE_WITH_DONE=`grep -n DONE $LOGFILE | tail -1 | cut -d : -f 1`

print INITIAL LAST LINE IS $LAST_LINE_WITH_DONE

while sleep 5; do

  NEWLAST_LINE_WITH_DONE=`grep -n DONE $LOGFILE | tail -1 | cut -d : -f 1`
   if [[ $LAST_LINE_WITH_DONE != $NEWLAST_LINE_WITH_DONE ]]; then
     print NEW LAST LINE IS $NEWLAST_LINE_WITH_DONE
     break;
   fi
done

This User Gave Thanks to chatguy For This Post:
hanson44
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