Homework 5

Due Date: Friday, June 7, 2002, at 11:59PM; no late assignments accepted	Points: 100

UNIX System

1.	(10 points) I want to make the file libprog.a in my home directory available to everyone so they can copy it, but I 
do not want anyone to be able to see any other files in my home directory.  How should I set the "other" bits of 
my directory's protection mask to do this?

2.	(10 points) What command would you use to remove columns from a file??

C Programming

3.	(50 points) Write a program called fileinfo that prints the following information about the files named on the 
command line:

·	file name

·	device inode number resides on

·	file inode number

·	file generation number

·	file type; if symbolic link, name of file the link points to

·	owner (as both login name if known and UID)

·	group (as both group name if known and GID)

·	owner rights (as "read", "write", "execute")

·	group rights (as "read", "write", "execute")

·	world rights (as "read", "write", "execute")

·	other sttributes ("setuid", "setgid", "sticky")

·	size in bytes

·	size in blocks (1 block = 1024 bytes; any leftover bytes counts as 1 block)

·	time of last access (in human-readable form)

·	time of last modification (in human-readable form)

·	time of inode creation (st_ctime; in human-readable form)

	Hint: Look at the manual page for stat(2) to see how to get this information. Use ctime(3) to convert the dates 
from internal to human-readable form; use readlink(2) to figure out to which file a symbolic link points

4.	(30 points)  Consider an array of characters.  Let bits 0-7 be the bits of array element 0, bits 8-15 the bits of array 
element 1, and so forth.  The bits for each character are numbered high-to-low, so the character `e' (hexadecimal 
65) has bit 7 set to 0, bit 6 set to 1, bit 5 set to 1, bit 4 set to 0, bit 3 set to 0, bit 2 set to 1, bit 1 set to 0, and bit 0 
set to 1. Write C preprocessor macros to do the following:

a.	Set the nth bit of char array buf to val:

SET_BIT(buf, n, val)

b.	Get the value of the nth bit of char array buf:

GET_BIT(buf, n)

Extra Credit

5.	(10 points) Modify the program you wrote in problem 3 to take an argument, -L. If this argument is given and the 
file is a smbolic link, print information about the file named by the symbolic link.