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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 HPUX

logsave

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

NAME

       logsave - save the output of a command in a logfile

SYNOPSIS

       logsave [ -asv ] logfile cmd_prog [ ... ]

DESCRIPTION

       The  logsave  program  will  execute  cmd_prog with the specified argument(s), and save a copy of its output to logfile.  If the containing
       directory for logfile does not exist, logsave will accumulate the output in memory until it can be written out.	A copy of the output  will
       also be written to standard output.

       If  cmd_prog  is a single hyphen ('-'), then instead of executing a program, logsave will take its input from standard input and save it in
       logfile

       logsave is useful for saving the output of initial boot scripts until the /var partition is mounted,  so  the  output  can  be  written	to
       /var/log.

OPTIONS

       -a     This option will cause the output to be appended to logfile, instead of replacing its current contents.

       -s     This  option  will  cause  logsave  to  skip writing to the log file text which is bracketed with a control-A (ASCII 001 or Start of
	      Header) and control-B (ASCII 002 or Start of Text).  This allows progress bar information to be visible to the user on the  console,
	      while not being written to the log file.

       -v     This option will make logsave to be more verbose in its output to the user.

AUTHOR

       Theodore Ts'o (tytso@mit.edu)

SEE ALSO

       fsck(8)

E2fsprogs version 1.44.1					    March 2018								LOGSAVE(8)
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