The program is being coded in C for use on Linux. I am currently using Ubuntu 16.04

For this assignment you will write a program that implements

some of the functions of the Unix du command. In doing so,

you will have a chance to work with the Unix directory

structure, recursion, and the stat() system call.

Explanation of du

The du utility tells how much disk space is being used in

each directory in a directory tree. It lists all the direc-

tories below a specified point and tells how many disk

blocks are used by the files and directories in and below

that point.

Here is an example:

$ du

8 ./hw3

8 ./hw2/hw4

16 ./hw2

32 .

The Assignment

Write a version of du (called dulite) that accepts zero or

one argument and accepts the -k option.

If it is called with no arguments, it processes the current

directory. If it receives a filename, it reports the number

of 512-byte blocks used by that file. If the argument names

a directory, dulite processes that directory and its chil-

dren. The output should match the output of the `real' du.

The -k option causes du to report the number of 1024-byte

blocks used.

dulite

Getting Started

3. When du encounters a subdirectory, du has to process that

directory recursively. How does du distinguish a regular

file from a subdirectory? Look at the header file for

stat.h and/or read the code for stat2.c in Week 4 folder.

Note that du prints the path to each subdirectory. How does

that work?

4. Write a function called disk_usage( char *path ) This

function opens the directory, reads it entry by entry, and

adds up the space used by each item in that directory. In

addition if any entry in the directory is a directory, then

disk_usage() will have to create a new string to hold the

new path and pass that string to itself. Use malloc() to

create the string: a fixed size buffer is liable to run out

when you least expect it.

Testing Your Program

You can make up your own test system data. Be sure to include

files and folders in your directory tree. I will have a preset

directory with some files that I expect to get consistent

results for all versions I run it on assuming there are no

errors in your program.

Error Handling

All sorts of errors can occur when traversing a directory

tree. You may be denied permission to a directory. You may

be unable to stat a file. You may encounter a very deep

directory structure with a long path name. How does the

dulite

real du handle those? Does it quit or report an error and

proceed? Do what it does.

What to Hand in

Hand in source code, a Makefile, a README file, a project

plan(flow chart), and a typescript of output from your test

run mentioned above, and any other amusing examples you might

want to include. Submit an electronic copy to the

drop box in Angel.

Note: Two Versions of du on Ice

There are two versions of du on ice. A Gnu version is

/usr/local/bin/du, and a OSF/1 version is /usr/bin/du. The

Gnu version uses 1K units unless the environment variable

POSIXLY_CORRECT is set. It is easier to test your program

against /usr/bin/du .

Extra Credit

A file may have more than one link. The correct action is

to count the disk usage only once, not for each link. For

an extra five points, write your program so it handles hard

links correctly.