Variable scope in bash Post: 302589363

Sponsored Content

Top Forums Shell Programming and Scripting Variable scope in bash Post 302589363 by methyl on Wednesday 11th of January 2012 12:04:45 PM

01-11-2012

Registered User

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)?

methyl

View Public Profile for methyl

Find all posts by methyl

10 More Discussions You Might Find Interesting

1. Programming

C++ variable scope and mutexes

I've been wondering if I can make mutexes much easier to use in C++ with creative use of a locking class and variable scope, but I'm not sure if things happen in the order I want. Here's pseudocode for something that could use the class: int someclass::getvalue() { int retval; ...

2. Shell Programming and Scripting

problem with shell variable's scope

Hi, I am stuck while developing a shell sub-routine which checks the log file for "success" or "failure". The subroutine reads the log file and checks for key word "success", if found it set the variable (found=1). It returns success or failure based on this variable. My problem is, I can...

3. Shell Programming and Scripting

scope of the variable - Naga

Hi All, I am new to unix shell scripting, in the below script "num" is an input file which contains a series of numbers example : 2 3 5 8 I want to add the above all numbers and want the result finally outside the while loop. it prints the value zero instead of the actual expected...

4. Shell Programming and Scripting

variable scope

Hi, I want to know about the variable scope in shell script. How can we use the script argument inside the function? fn () { echo $1 ## I want this argument should be the main script argument and not the funtion argument. } also are there any local,global types in shell script? if...

5. UNIX for Dummies Questions & Answers

Bash loops and variable scope

Hi All, I've been researching this problem and I am pretty sure that the issue is related to the while loop and the piping. There are plenty of other threads about this issue that recommend removing the pipe and using redirection. However, I haven't been able to get it working using the ssh and...

6. Shell Programming and Scripting

Help with retaining variable scope

Hi, I use Korn Shell. Searched Forum and modified the way the file is input to the while loop, but still the variable does not seem to be retaining the final count. while read name do Tmp=`echo $name | awk '{print $9 }'` Count=`cat $Tmp | wc -l`...

7. Shell Programming and Scripting

Maintain Scope of the variable in UNIX

Hi All Is there is any way to maintain the scope of the variable in unix Example x=1 j=1 while do .. .... .... while do .. .. x=x+1 done #inner most while loop ends here done #outer loop ends here

8. Shell Programming and Scripting

BASH: variable and function scope and subscripts

Hi, I'm a Delphi developer new to linux, new to this forums and new to BASH programming and got a new task in my work: maintaining an existing set of BASH scripts. First thing I want to do is making the code more reliable as in my opinion it's really bad written. So here's the quest: I'm...

9. Programming

Variable Scope in Perl

I have to admit that i have not used Perl at all and this is a singular occasion where i have to patch an existing Perl script. I dearly hope i do not have to do it again for the next 15 years and therefore try to avoid having to learn the programming language in earnest. The OS is AIX 7.1, the...

10. UNIX for Beginners Questions & Answers

Bash Variable scope - while loop while reading from a file

Cope sample1: test.sh i=0 echo " Outside loop i = $i " while do i=$(( $i + 1)) echo "Inside loop i = $i " done echo " Out of loop i is : $i " When run output : Outside loop i = 0 Inside loop i = 1 Inside loop i = 2 Inside loop i = 3 Inside loop i = 4 Inside loop i = 5 Inside...

LEARN ABOUT SUSE

rbash

RBASH(1)						      General Commands Manual							  RBASH(1)

NAME

       rbash - restricted bash, see bash(1)

RESTRICTED SHELL

       If  bash  is  started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted.  A restricted shell is
       used to set up an environment more controlled than the standard shell.  It behaves identically to bash with the exception that the  follow-
       ing are disallowed or not performed:

       o      changing directories with cd

       o      setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV

       o      specifying command names containing /

       o      specifying a filename containing a / as an argument to the .  builtin command

       o      specifying a filename containing a slash as an argument to the -p option to the hash builtin command

       o      importing function definitions from the shell environment at startup

       o      parsing the value of SHELLOPTS from the shell environment at startup

       o      redirecting output using the >, >|, <>, >&, &>, and >> redirection operators

       o      using the exec builtin command to replace the shell with another command

       o      adding or deleting builtin commands with the -f and -d options to the enable builtin command

       o      using the enable builtin command to enable disabled shell builtins

       o      specifying the -p option to the command builtin command

       o      turning off restricted mode with set +r or set +o restricted.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script.

SEE ALSO

       bash(1)

GNU Bash-4.0							    2004 Apr 20 							  RBASH(1)

10 More Discussions You Might Find Interesting

1. Programming

C++ variable scope and mutexes

Discussion started by: Corona688

2. Shell Programming and Scripting

problem with shell variable's scope

Discussion started by: cjjoy

3. Shell Programming and Scripting

scope of the variable - Naga

Discussion started by: nagnatar

4. Shell Programming and Scripting

variable scope

Discussion started by: shellwell