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Full Discussion: Logfile monitoring with logfile replacement
Top Forums Shell Programming and Scripting Logfile monitoring with logfile replacement Post 302925234 by Warluck on Friday 14th of November 2014 06:33:36 PM
Old 11-14-2014
Logfile monitoring with logfile replacement
Bonjour,
I've wrote a script to monitor a logfile in realtime. It is working almost perfeclty except for two things.

The script use the following technique :
Code:
tail -fn0 $logfile | \
while read line ; do
... some stuff
done

First one, I'd like a way to end the monitoring script if a certain string in sent to the logfile. I have used BREAK and EXIT which work but only at the next pass of the loop. Just to be sure I am clear :
Pass 1 of the loop, find the string that ends the script, send break to the loop.
No exit until Pass 2 of the loop that occurs when a new line is inserted to the logfile

I would like to end the script right away and not wait a new line to be added to the monitored logfile.

Second thing. I would like a way to reset the script, explain :

Sometimes, I need to delete(rotate) the logfile and create a new one. When I do that, my monitor script continues to run but seems to "lose" the logfile, I need to kill the script and launch it anew. Is there a way to tell the script restart the loop with the new log without having to end the script?

thanks for your time and expertise.

Regards

---------- Post updated at 06:33 PM ---------- Previous update was at 06:20 PM ----------

I am having a quick answer to my second question. I use tail -F instead of tail -f, the "-F" tells tail to follow the file and retry which is exactly what I want.
 

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LEARN ABOUT OSF1

log

log(8)							      System Manager's Manual							    log(8)

NAME

       log - Records input and output from a program

SYNOPSIS

       /usr/sbin/log <logfile> <command>

OPERANDS

       The file in which to record the interaction being logged.  The command to execute.

DESCRIPTION

       The  log  program  runs <command> and logs the input to and output from <command> to the <logfile> file.  Input and output are logged until
       <command> exits, the log program exits, and the exit status of <command> is returned.

       The log program is used by the system  installation  procedure  and  the  it(8)	command  to  create  the  /var/adm/smlogs/install.log  and
       /var/adm/smlogs/it.log installation log files.

RESTRICTIONS

       Because	the  log  program is used in the installation standalone environment, program size was the greatest concern in its implementation.
       The log program does not search for the PATH variable to locate <command> and error messages are terse.

       The log program causes <command> to take standard input from and write standard output and standard error to  UNIX  pipes.   Some  commands
       will  not  be able to operate in this environment; therefore, it is suggested that you use the script(1) command instead.  UNIX shells will
       not issue prompts when run from log unless the shell is started with an explicit interactive switch (-i for most shells).  For example, log
       foo.tmp /sbin/sh -i

       In the previous example, foo.tmp is the name of <logfile>.

       The  log  program  intercepts  end-of-file (usually Ctrl/d).  Therefore programs which normally receive end-of-file as an exit command must
       exit by some other means.

ERRORS

       Log open error

   Explanation:
       The log program was unable to open <logfile>. Verify that the directory exists and that ownerships and permissions are set correctly.

       Exec Error

   Explanation:
       The log program was unable to execute <command>. Verify that you specified a full pathname for <command> and  that  <command>  is  an  exe-
       cutable file.

       Fork Error

   Explanation:
       The log program was unable to create one of the processes it requires to log data.

SEE ALSO

       Commands: it(8), script(1)

																	    log(8)
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