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Full Discussion: Variable scope in bash
Top Forums Shell Programming and Scripting Variable scope in bash Post 302589363 by methyl on Wednesday 11th of January 2012 12:04:45 PM
Old 01-11-2012
The script is not slow for its content.
The "sar -d 30 4" statement will take 2 minutes (sample interval of thirty seconds times the four iterations). On my test the script took 2 mins 3 secs.

The process to fish out the Average lines can be improved such that we only read $TEMP1 once.

Code:
#!/bin/sh
PATH=/usr/bin:/usr/sbin:/sbin; export PATH
TEMP1="/tmp/raw-sar-output.txt$$"
TEMP2="/tmp/sorted-sar-output.txt$$"
CONT=0
sar -d 30 4 > $TEMP1
grep \^"Average" $TEMP1 | awk '{ print $5,$2 }' | sort -k 1n,1 > $TEMP2
if [ -s "$TEMP2" ]
then
   while read file;
   do
      IO=`echo $file | awk '{ print $1 }'`
      TMP_VAL=`echo $file | awk '{ print $1 }'`
      CONT=`expr $CONT + $TMP_VAL`
   echo CONT = $CONT
   done < $TEMP2
   #Echo Result
   echo $CONT
else
   rm -f $TEMP1 $TEMP2 2>/dev/null
   exit 1
fi
rm -f $TEMP1 $TEMP2 2>/dev/null
exit 0


If performance was really important, there is no need for the workfile $TEMP1 and (as Corona688 notes) the maths can be done in awk.

The other issue with your script is possibly the design. Field 5 in "sar" is the Number of Read+Write data transfers PER SECOND. Over the sample period of just 2 minutes you need some decent level of disc activity to get this figure above zero.

Finally the question I should have asked first:
Please explain the statement "execution is too slow and causes problems to the use I need it for".


(You are aware that unix systems can be configured to accumulate "sar" statistics automatically all day every day)?
 

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LEARN ABOUT OPENDARWIN

sa2

sa2(8)							    BSD System Manager's Manual 						    sa2(8)

NAME

     sa2 -- Generate a system activity daily report file.

SYNOPSIS

     /usr/lib/sa/sa2 [-dgpu] [-n mode] [-e time] [-f filename] [-i seconds] [-s time]

DESCRIPTION

     The sa2 command is a shell script used to invoke the system activity reporter sar for purposes of generating the standard default daily
     report file.  The report file generated is, /var/log/sa/sardd where the dd represents the current day of the month.  The sa2 options are the
     same as those documented in sar(1).

     When sa2 runs, it will also remove data and report files, found in /var/log/sa, that are more than one week old.

     The sa2 command is intended to be started by cron.

EXAMPLE CRON ENTRY

     # Starting at 8am collect system activity records
     # every 20 minutes for 12 hours
     # 20 minutes = 1200 seconds
     # 12 hours with 3 samples each hour = 36 loops

     0 8 * * 1-5 /usr/lib/sa/sa1 1200 36

     # After the 12 hour period,
     # collect a system activity report

     30 20 * * 1-5 /usr/lib/sa/sa2 -A

FILES

     /var/log/sa/sardd	Default daily report file.
     /var/log/sa/sadd	Default daily data file.

			dd are digits that represent the day of the month.

SEE ALSO

     sa1(8), sadc(8), sar(1), iostat(8), vm_stat(1), netstat(1), top(1), sc_usage(1), fs_usage(1), crontab(1), crontab(5)

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