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Top Forums UNIX for Advanced & Expert Users Trapping a kill command sent to a script and using it to send an EOF to a subprocess before killing Post 302880579 by DeCoTwc on Friday 20th of December 2013 04:55:13 PM
Old 12-20-2013
Trapping a kill command sent to a script and using it to send an EOF to a subprocess before killing

I originally had a script written in pure shell that I used to parse logs in real time and create a pipe delimited file that only contained errors. It worked but it was using a lot of memory (still not clear on why). I originally got around this by writing a wrapper for the script that ran on cron and periodically killed the script and started a new instance. This worked for a while, but was still too heavy. So, I rewrote the parsing logic in awk instead of shell and the memory and CPU utilization dropped completely.

So now, I have this script running, but every 15 minutes the cronjob kills it and starts a new instance. What I want to do now is have my awk section of the script building out arrays, and when the cron kicks in, it sends an EOF to the awk so it can dump it's info into a separate file before it's killed and a new instance is started. Below is my code. What I want to do is add blocks to the awk section that creates arrays, and then add an end block to it that dumps the values from those arrays into a file. So, I need to trap the kill command and then have it send an EOF to awk, then kill the script and start a new instance.


Code:
#!/bin/bash
######################################################
# Program:      logGen.sh
# Date Created: 22 Aug 2012
# Description:  parses the manager log in real time into daily error files
# Date Updated: 27 Nov 2013
#		|_moved all data parsing logic to awk instead of shell
#		|_Need to analyze memory/CPU usage and consider changing
#		|_restart frequency in cron
# Developer:    Redacted (Senior Support Engineer)
######################################################
#Prefix for pid file
pidPrefix="logGen"
#output direcory
outDir="/opt/Redacted/logs/allerrors/"
#Simple function to see if running on primary
checkPrime ()
{
  if /sbin/ifconfig eth0:0|/bin/grep -wq inet;then isPrime=1;else isPrime=0;fi
}


#function to kill previous instances of this script
killScript ()
{
  /usr/bin/find /var/run -name "${pidPrefix}.*.pid" |while read pidFile;do
    if [[  "${pidFile}" != "/var/run/${pidPrefix}.${$}.pid" ]];then
      /bin/kill -- -$(/bin/cat ${pidFile})
      /bin/rm ${pidFile}
    fi
  done
}


#Check to see if primary
#If so, kill any previous instance and start log parsing
#If not, just kill leftover running processes

checkPrime
if [[ "${isPrime}" -eq 1 ]];then
  echo "$$" > /var/run/${pidPrefix}.$$.pid
  killScript
  tail -F -n0 /opt/Fabrix.TV/logs/manager_proxy.log|awk -v dir=$outDir '{OFS="|"}
{
  if ($3 == "E")
  {
    file="allerrors."$1".log"
    gsub("/",".",file)
    if ($9 ~ /@/)
      print $1,$2,$8,$9,substr($0, index($0,$10)) >> dir file
    else {if ($8 !~ /@/)
      print $1,$2,$7,"NULL",substr($0, index($0,$8)) >> dir file
    }
    fflush(stdout);
  }
}'
else
  killScript
  exit 0
fi

 

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SCRIPT(1)							   User Commands							 SCRIPT(1)

NAME
script - make typescript of terminal session SYNOPSIS
script [options] [file] DESCRIPTION
script makes a typescript of everything displayed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves the dialogue in this file. If no filename is given, the dialogue is saved in the file type- script. OPTIONS
-a, --append Append the output to file or to typescript, retaining the prior contents. -c, --command command Run the command rather than an interactive shell. This makes it easy for a script to capture the output of a program that behaves differently when its stdout is not a tty. -e, --return Return the exit code of the child process. Uses the same format as bash termination on signal termination exit code is 128+n. -f, --flush Flush output after each write. This is nice for telecooperation: one person does `mkfifo foo; script -f foo', and another can supervise real-time what is being done using `cat foo'. --force Allow the default output destination, i.e. the typescript file, to be a hard or symbolic link. The command will follow a symbolic link. -q, --quiet Be quiet (do not write start and done messages to standard output). -t[file], --timing[=file] Output timing data to standard error, or to file when given. This data contains two fields, separated by a space. The first field indicates how much time elapsed since the previous output. The second field indicates how many characters were output this time. This information can be used to replay typescripts with realistic typing and output delays. -V, --version Display version information and exit. -h, --help Display help text and exit. NOTES
The script ends when the forked shell exits (a control-D for the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. script works best with commands that do not manipulate the screen, the results are meant to emulate a hardcopy terminal. It is not recommended to run script in non-interactive shells. The inner shell of script is always interactive, and this could lead to unexpected results. If you use script in the shell initialization file, you have to avoid entering an infinite loop. You can use for example the .profile file, which is read by login shells only: if test -t 0 ; then script exit fi You should also avoid use of script in command pipes, as script can read more input than you would expect. ENVIRONMENT
The following environment variable is utilized by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism), scriptreplay(1) HISTORY
The script command appeared in 3.0BSD. BUGS
script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. script is primarily designed for interactive terminal sessions. When stdin is not a terminal (for example: echo foo | script), then the session can hang, because the interactive shell within the script session misses EOF and script has no clue when to close the session. See the NOTES section for more information. AVAILABILITY
The script command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils /util-linux/>. util-linux June 2014 SCRIPT(1)
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