CSC352: Using Bash Scripts to Measure Program Execution Time

--D. Thiebaut (talk) 13:41, 11 September 2013 (EDT)

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This page illustrates how to use a Bash script to run a Java program multiple times while passing it a different parameter every time.

A simple Java Program

Note that the program gets the value of the variable N from the command line.

class PrintN {
 
     public static void main( String[] args ) {
 
         int N = Integer.parseInt( args[0] );
         System.out.println( "I got " + N );
     }
 
 }

Running the program 10 times from the command line

• Running the program above 10 times can be done as follows, from the command line:

   bash
   javac PrintN.java
   for i in 1 2 3 4 5 6 7 8 9 10 ; do
      java PrintN $i
   done

Running the program from a Bash script

The script is shown below:

#! /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

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

Measuring the Execution Time of the Program

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:

#! /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

Note that Linux also supports another time command, located in /usr/bin. It gives more information in a less readable format:

#! /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