Variable gets auto updated after function execution Post: 303036761

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Top Forums UNIX for Beginners Questions & Answers Variable gets auto updated after function execution Post 303036761 by MadeInGermany on Wednesday 10th of July 2019 03:38:44 PM

07-10-2019

Registered User

grep -q might not work with all grep versions. What is your OS?

Code:

tail -f $UMPath/data/nirvana.log | while read line
do
done

Several problems with that.
The pipe forces the while-do-done block into a sub shell.

While the return should work an exit can produces different results, dependent on the shell. BTW what shell and OS do you use?
Your main problem: changes on variables are not copied back to the main shell.

Then, if the sub shell terminates, it sends a SIGPIPE to the tail -f that hopefully terminates.
The following eliminates some problems

Code:

# Watch the log file for the initialization string
getline()
{
# use the portable printf in favor of echo -e
printf "\nNow watching nirvana log for the Started Nirvana Realm string"
# tail -f will hopefully terminate
tail -f $UMPath/data/nirvana.log |
# the pipe forces the while-do-done into a sub shell:
# variables are not returned but a return value should work
while read line
do
    case "$line" in
    *"Realm Server Startup sequence completed"*)
        printf "\nFound: %s\n\n" "$line"
        return 0
    ;;
    *"Server shutdown"*)
        printf "\nFound: %\n\n" "$line"
        return 1
    ;;
    esac
done
}
# act on the return value
if getline
then
    echo "UM is now up and running"
else
    echo "UM failed to start. Please check"
    rval=1
fi
exit $rval

MadeInGermany

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LEARN ABOUT DEBIAN

logtop

LOGTOP(1)						      General Commands Manual							 LOGTOP(1)

NAME

       logtop - Realtime log line rate analyser

SYNOPSIS

       logtop [OPTIONS]

DESCRIPTION

	logtop is a System Administrator tool analyzing line rate on stdin.
	It reads on stdin and print a constantly updated result
	displaying, in columns:
	Line number, count, frequency, and the actual line.

	 $ tail -f FILE | logtop
	is the friendly version of:
	 $ watch 'tail FILE | sort | uniq -c | sort -gr'

OPTIONS

       -s, --size=K
	      Only keep K lines in memory, instead of 10000.

       -q, --quiet
	      Do not display a live view of the data, only display a top at exit.

       -l, --line-by-line=K
	      Print result line by line, in a machine friendly format, K is the number of result to print per line.

		Line by line format is : [%d %f %s	]*

		  %d : Number of occurences
		  %f : Frequency of apparition
		  %s : String (Control chars replaced by dots.

       -i, --interval=K
	      Interval between graphical updates, in seconds. Defaults to 1.

       -h, --help
	      Show summary of options.

       -v, --version
	      Show version of program.

EXAMPLES

       Here are some logtop usage examples.

       tail -f cache.log | grep -o "HIT|MISS" | logtop

       Realtime hit / miss ratio on some caching software log file.

       tail -f access.log | cut -d' ' -f1 | logtop -s 10000

       Realtime most querying IPs on your server, as long as log lines in access.log starts with the client IP.

       tail -f access.log | cut -d' ' -f7 | logtop -s 10000

       Realtime most requested web pages in a NCSA like log file.

       cat auth.log | grep -v "CRON" | grep -o ": .*" | logtop -q -s 100000

       Display a one-shot simple analyse of your auth.log.

SEE ALSO

       watch(1)

AUTHOR

       logtop was written by Julien Palard.

       This manual page was written by Julien Palard <julien@palard.fr>, for the Debian project (and may be used by others).

								  April 16, 2011							 LOGTOP(1)

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