View source for CSC352: Using Bash Scripts to Measure Program Execution Time

--[[User:Thiebaut|D. Thiebaut]] ([[User talk:Thiebaut|talk]]) 13:41, 11 September 2013 (EDT)
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<bluebox>
This page illustrates how to use a Bash script to run a Java program multiple times while passing it a different parameter every time.
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=A simple Java Program=
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Note that the program gets the value of the variable ''N'' from the command line.
<source lang="java">
class PrintN {
 
     public static void main( String[] args ) {
 
         int N = Integer.parseInt( args[0] );
         System.out.println( "I got " + N );
     }
 
 } 
</source>
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=Running the program 10 times from the command line=

* Running the program above 10 times can be done as follows, '''from the command line''':
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::<source lang="bash">
    bash
    javac PrintN.java
    for i in 1 2 3 4 5 6 7 8 9 10 ; do
       java PrintN $i
    done
</source>
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=Running the program from a Bash script=

The script is shown below:
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::<source lang="bash">
#! /bin/bash
# runPrintN.sh
#
 
javac PrintN.java
for i in 1 2 3 4 5 6 7 8 9 10 ; do
    java PrintN $i
done
</source>
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Make sure you make the script executable before you call it:

  
  chmod a+x runPrintN.sh


You can now run the program 10 times with just one command:

  ./runPrintN.sh
  I got 1
  I got 2
  I got 3
  I got 4
  I got 5
  I got 6
  I got 7
  I got 8
  I got 9
  I got 10

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=Measuring the Execution Time of the Program=
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:An easy way to measure the execution time of each time we run the program is to use the '''time''' Linux command, as illustrated below:
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::<source lang="bash">
#! /bin/bash
# runPrintN.sh
# 
javac PrintN.java
for i in 1 2 3 4 5 6 7 8 9 10 ; do
    #java PrintN $i
    time java PrintN $i
done
</source>
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:Note that Linux also supports another '''time''' command, located in /usr/bin.  It gives more information in a less readable format:
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::<source lang="bash">
#! /bin/bash
# runPrintN.sh
# 
javac PrintN.java
for i in 1 2 3 4 5 6 7 8 9 10 ; do
    #java PrintN $i
    /usr/bin/time java PrintN $i
done
</source>
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[[Category:CSC352]][[Category:bash]][[Category:Java]]