Unix System Calls and Library Functions
The goal of this homework is to become familiar with the environment in hoare while practising system calls.
Do Exercise 5.8:Traversing Directories (p. 179) in your text by Robbins/Robbins. You only need to do the Example 5.38, or
breadth-first traversal.
The programming task requires you to create a utility to traverse a specified directory in breadth-first order. Breadth-first search
explores all the nodes at a given level before descending lower in the tree. Breadth-first search is implemented with a queue.
As the program encounters each directory node at a particular level, it enqueues the pathname for later examination. You can
use the following pseudocode which makes use of queue ADT. You will have to provide the code for queue ADT operations
yourself.
breadthfirst ( root )
{
enqueue ( root );
while ( ! empty ( queue ) )
{
next = dequeue ( queue );
for each node directly below next
{
visit ( node );
if ( isa_directory ( node ) )
enqueue ( node );
}
}
}
The indentation of the filenames shows the level in the file system tree. Use the output format specified in Example 5.37, with
a default indentation of 4 spaces for each level in the directory. You should be able to change the indentation spaces by using
an option on command line followed by a number. The executable should be called bt. The program will be invoked by:
bt [-h] [-L -d -g -i -p -s -t -u -In | -l] [dirname]
The options are to be interpreted as follows:
h Print a help message and exit.
L Follow symbolic links, if any. Default will be to not follow symbolic links.
t Print information on file type.
p Print permission bits as rwxrwxrwx.
i Print the number of links to file in inode table.
I n Indent by n spaces.
Unix System Calls 2
u Print the UID associated with the file.
g Print the GID associated with the file.
s Print the size of file in bytes. If the size is larger than 1K, indicate the size in KB with a suffix K; if the size is larger than
1M, indicate the size in MB with a suffix M; if the size is larger than 1G, indicate the size in GB with a suffix G.
d Show the time of last modification.
l This option will be used to print information on the file as if the options tpiugs are all specified.
If the user does not specify dirname, run the command using current directory and print the tree accordingly. The output will
appear as follows:
$ ls -I 4 -l proj
proj drwx------ 10 sanjiv faculty 4K Nov 25, 2003
bi_scan drwx------ 3 sanjiv faculty 4K Jul 06, 2004
include drwx------ 3 sanjiv faculty 4K Nov 25, 2003
CVS drwx------ 2 sanjiv faculty 4K Nov 25, 2003
Makefile -rw------- 1 sanjiv faculty 712 Nov 25, 2003
Makefile.Linux -rw------- 1 sanjiv faculty 1K Nov 25, 2003
CVS drwx------ 2 sanjiv faculty 4K Nov 25, 2003
cluster.h -rw------- 1 sanjiv faculty 5K Nov 25, 2003
config.h -rw-r--r-- 1 sanjiv faculty 5K Jan 22, 2004
Entries -rw------- 1 sanjiv faculty 336 Nov 25, 2003
Repository -rw------- 1 sanjiv faculty 24 Nov 25, 2003
Root -rw------- 1 sanjiv faculty 15 Nov 25, 2003
Entries -rw------- 1 sanjiv faculty 650 Nov 25, 2003
Repository -rw------- 1 sanjiv faculty 24 Nov 25, 2003
Root -rw------- 1 sanjiv faculty 15 Nov 25, 2003
With the use of perror, I’ll like some meaningful error messages. The format for error messages should be:
bt: Error: Detailed error message
where bt is actually the name of the executable (argv[0]) and should be appropriately modified if the name of executable is
changed without recompilation.
What to handin
Create your programs in a directory called username.1 where username is your user name on hoare. Once you are done with
everything, remove the executables and object files, and issue the following commands:
% cd
% ˜sanjiv/bin/handin cs4760 1
Do not forget Makefile (with suffix or pattern rules), RCS and README for the assignment. If you do not use RCS, you will
lose 10 points. I want to see the log of how the program files are modified. Therefore, you should use keyword substitution
within RCS inside your source files.