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Full Discussion: Problem with nohup use in scripting
Top Forums Shell Programming and Scripting Problem with nohup use in scripting Post 302538582 by Corona688 on Wednesday 13th of July 2011 12:05:46 PM
Old 07-13-2011
I see a few things problematic with this:

Code:
alarm_file_array="test1.alarms test2.alarms test3.alarms test4.alarms"
for file in ${alarm_file_array[@]}
do
	nohup tail -f $file |awk 'NR>10' >> output.alarms 2>/dev/null &
done

First and foremost, if you did get all three of these pipe chains writing to output.alarms independently, they wouldn't know or care about each other -- they'd just write whatever they want, wherever they want, whenever they want, potentially overwriting each others' contents. You should have a separate logfile for each tail.

Second of all, 'tail' and 'awk' are separate processes. The warning message is coming from the standard error of tail, and you're only redirecting awk.

Third of all, you're only putting awk in the background, not tail, which is why tail hangs -- not because of nohup.

Fourth, it makes no sense to use nohup at the start of a pipe chain, because it does what it says it's doing -- sends its stdout into nohup.out and not into the pipe feeding into awk.

You can achieve a similar effect to nohup by redirecting all streams to /dev/null, which will work for the entire pipe chain. You can also put an entire subshell in the background with ( ) .

Code:
alarm_file_array="test1.alarms test2.alarms test3.alarms test4.alarms"
for file in ${alarm_file_array[@]}
do
        (   exec 0</dev/null # stdin
            exec 1>/dev/null # stdout
            exec 2>/dev/null # stderr
            tail -f $file |awk 'NR>10' >> ${file}.out ) &
      disown
done

The 'disown' is so the script won't wait for the background jobs to finish before it quits. Some shells don't have disown, but those wouldn't wait for background jobs anyway.
 

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LEARN ABOUT HPUX

kcmond

kcmond(1M)																kcmond(1M)

NAME

       kcmond - EMS Kernel Tunable Monitor daemon

SYNOPSIS


		kcmond

DESCRIPTION

       The  kcmond  daemon  monitors  the consumption of kernel resources. It is an Event Monitoring Services (EMS - see ems(5)) monitor. The data
       collected by kcusage can be displayed by kcusage(1M).

       kcmond includes a resource dictionary file (/etc/opt/resmon/dictionary/kcmond_01.dict) which is used by EMS to identify resources for moni-
       toring.

       Users can control the monitoring of each kernel tunable by setting a percentage value for the consumption of that resource. For example, if
       the user sets a value of 75 for nproc, the Kernel Tunable Monitor will report an event when the number of  processes  reaches  75%  of  the
       nproc setting.

       The  kcalarm(1M) command is used to add, modify and delete kernel tunable alarms. The kcusage(1M) command is used to view data collected by
       kcmond. The kcweb(1M) command provides a Web-based, graphical user interface to control alarms and view usage data, including graphs of the
       usage data.

       kcmond is a light weight daemon that will exit after being idle for ten minutes.

SUPPORTED PARAMETERS

       For a complete list of the kernel tunables that can be monitored with this daemon, see the kcusage(1M) manpage.

DEPENDENCIES

       kcmond must be run by the registrar process of the Event Monitoring Service (EMS) and is not designed to be run from the command line.

AUTHORS

       was developed by Hewlett-Packard.

FILES

       Executable.

       The  resource dictionary for kcmond, describes the location (e.g. /system/kernel_tunables/nproc) of kernel tunables in the resource hierar-
       chy and references kcmond as the resource monitor.

       Log file for the entire Resource Monitor Framework, including kcmond. Any errors are logged here.

SEE ALSO

       kcalarm(1M), ems(5), kcusage(1M)

																	kcmond(1M)
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