Module 8 (Lectures 34-37) File systems
1. Create a text file called Testfile of size 5 KBytes on the hard disk of your system.
Copy it to a flash memory stick. Write a program to display the contents of a file
as follows: read the first 512Bytes and print them out to stdout. Then read the next
512Bytes and print them out to stdout, etc. You can structure this as a for loop
that iterates 10 times. Measure the execution time of the program when used to
display the file Textfile (i) from your hard disk, (ii) from your flash memory
stick. What do you observe from the measurements?
2. Instrument the program that you wrote for question 6 to measure the execution
time for each of the 10 iterations of the for loop. Use this instrumented program to
display TextFile from the hard disk. What do you observe from the
measurements? Now, modify the program so that instead of displaying the entire
contents of the file, it displays the first 512Bytes of the file 10 times. Repeat the
measurements for this modified program. What do you observe from the
measurements?
3. Modify the program of question 6 to use memory mapped I/O instead of file
system operations. How does this affect the program execution time if the file is
(i) on hard disk, (ii) on flash memory stick.
4. The program cat available in Linux/UNIX provides the functionality required of
the program for question 6. Study the implementation of cat. Is it superior to that
of the programs that you have developed in the previous questions?
5. We have seen that files can be used as a means of Inter Process Communication
(IPC). Write a program which uses fork( ) to create a child process. The child
process prompts the user to type in a line of text, which it then reads in, writes
into a file called UserInput and exits. The parent process, which has been waiting
for the child process to exit, then reads the line of text from the file UserInput
and prints it to stdout.
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