Homework 5
Due Date: Friday, June 7, 2002, at 11:59PM;
no late assignments accepted
Points: 100
UNIX System
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(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?
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(10 points) What command would you use to remove columns from a file??
C Programming
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(50 points) Write a program called fileinfo that prints the
following information about the files named on the command line:
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file name
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device inode number resides on
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file inode number
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file type; if symbolic link, name of file the link points to
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owner (as both login name if known and UID)
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group (as both group name if known and GID)
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owner rights (as "read", "write", "execute")
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group rights (as "read", "write", "execute")
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world rights (as "read", "write", "execute")
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other sttributes ("setuid", "setgid", "sticky")
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size in bytes
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size in blocks (1 block = 1024 bytes; any leftover bytes counts as 1 block)
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time of last access (in human-readable form)
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time of last modification (in human-readable form)
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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
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(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:
- Set the nth bit of char array buf to val:
SET_BIT(buf, n, val)
- Get the value of the nth bit of char array buf:
GET_BIT(buf, n)
Extra Credit
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(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.
