Shell Programming and Scripting

I tried this one. Got "[: too many arguments " on the if condition. Any typos in the code below? Thanks.

A C/C++/JAVA/PERL/Python level app can keep track of where it has looked and just look at new areas much more easily. Shell has to live with tail -f or some sort of polling the whole file. You might be able to seek in shell using 'tail -####c', where you check between the last and current file size (from ls -l?), then reset the last file size to that current size. If the file size is the same, sleep some more.Rotating logs adds a whole new level of complexity. If you had checked file N up to byte M and it is rotated, you have to detect that and start with Byte M of file N at the new name, then move to the current file. You high water mark is a file number and a byte count.

I do have a single script for both Server Startup & Shutdown with parameters defining the operation & Search Keyword. In both cases, we are monitioring the same file.

There are two scripts - Startup & Shutdown. I added a line at the end of each to execute my script which reads the Server log file.

Once the server starts, we send a message to Syslog and stop reading the log file.

At a later point, when someone decides to stop the server using the shutdown script, it will again invoke my script (which looks for the SHUTDOWN keyword in the log file and send the message to syslog).





---------- Post updated at 11:58 AM ---------- Previous update was at 11:44 AM ----------

I dont have to be concerned about change in file name. Since, my source file name will not change though we have log files rotating.

File size will continually change. during startup, during the time server is up and when the server is shutdown.

Who is writing it when the server is shutdown? Wel, as it shuts down, and then it goes quiescent, I hope!

The idea is that tail -f on a pipe might not process the shutdown due to stuff stuck in the pipe. I think it does, but you seem to have problems, and tail version do vary. The alternative to tail -f if you have tail -####c that seeks, is something like:

Code:

seek=0
while :
 do
  sz=0`ls -l logfile | awk '{print $5}'`
  if (( sz == seek ))
   then
    sleep 1        # or whatever frequency you desire for quiet times
    continue
   fi
  tail -${seek}c $logfile | sed -n '
    /pattern1/w file1
    /pattern2/w file2
    /pattern3/w file3
    /pattern4/w file4
   '
  seek=$sz
 done

Since tail reads to EOF and ends, no data is trapped in the pipe. The sed approach allows you to write marker files for each critical message.

Pickett, I tried the below code. The logs just hung at a point, maybe before reaching the line, '$SERVER_STATUS'

Code:

 
seek=0
while :
do
sz=`ls -l nohup.out | sed '
s/^[^ ][^ ]* *[^ ][^ ]* *[^ ][^ ]* *[^ ][^ ]* *\([^ ][^ ]*\) .*/\1/
'`
if (( sz == seek ))
then
sleep 1
continue
fi
tail -${seek}c nohup.out | sed -n '
/$SERVER_STATUS'/w nohup.out
'
seek=$sz
done

On the topic of seeking with the shell, the following ksh93 operators may interest you:
Regards,
Alister

Well, you can *seek() to an offset, or you can search to a pattern, which is *read(). Many systems have ksh93 as dtksh in the CDE bin!

Yes, that loops forever. If you want it to break, make it 'while [ ! -f fileN ]', where fileN is the file created by sed w for the end pattern.