Given any directory, use the ls command to display:

$$ all files and sub$-$directories starting with the letter $$D$($note do not list anything

in any sub$-$ directory$)$

$$ its immediate sub$-$directories $($sub$-$directories only, and no other ordinary files$)$

$$ its immediate hidden sub$-$directories only $$ take a screenshot $($#$2-3)$ that clearly shows

the

command and the result.

$5.$ Assume that the following files are in the working directory:

$ ls

intro notesb ref$2$ section$1$ section$3$ section$4$b

notesa ref$1$ ref$3$ section$2$ section$4$a sentrev

Give commands for each of the following, using wildcards to express filenames with as few

characters as possible.

$$ List all files that begin with $$section$.$

$$ List $$section$1,$section$2,$ and $$section$33$ files only.

$$ List the $$intro$$ file only.

$$ List $$section$1,$section$3,$ref$1,$ and $$ref$34$ files only. Include the command in

thesubmission document $($#$2-4).$

$6.$ File copy, move, and removal. Use one command to finish each step. You should not use

$$cd$$ command at all.

$$ Under your home directory, create a new text file using your campus email id as the file

name.

$$ Create a copy of the file in the same directory using any name you like.

$$ Create a subdirectory $$backup$.$

$$ Move the original file to $$backup$$ and rename it using your first name.

$$ Create a copy of the $$backup$$ directory $($and all file in it$)$; name it $$backup$2.$

$$ Delete $$backup$.$

$$ Rename $$backup$2$ to $$backup$3.$

$$ List the files in the new directory. Take a screenshot $($#$2-5)$ that clearly shows the

command you

use and the result.

$7.$ Link

a$)$ Go to your $$Documents$$ directory;

b$)$ Create a file $$file$1$ with the text $$hello$$ in it;

c$)$ Create a hard link named $$file$2$ linked to $$file$1$;

d$)$ Create a soft link named $$soft$1$ linked to $$file$1$; create another soft link

named $$soft$2$ linked to $$file$2.$

e$)$ View information of the $4$ files $($what command should you use to produce some

output

same to the figure below$)$ what$$s the difference of these $4$ files?

f$)$ Are contents of the $4$ files the same? What command do you use to verify that?

g$)$ Create a hard link $$file$3$ linked to $$soft$1.$

h$)$ Use a text editor $($Nano or VIM$)$ to edit $$soft$2$: change $$hello$$ to $$hello$,$

world$.$ Now, what is the content in each of the $5$ files? Are they the same?

What if you change the text in any of these files?

i$)$ Rename $$file$1$ to $$change$.$ Now, how many files can you still open and view

the content?

Use the same command you used in step e$)$ to view file information. What$$s the

change?

j$)$ Use a text editor to edit $$file$3$: type $$Linux$$ and save. Now what will

happen? Which files share the same content? Why?

k$)$ List all files you have now $($use the $-$l option$).$ Take a screenshot $($#$2-6)$ of the

command and the result.

$8.$ Review questions $($discuss the ones you are not sure or totally confused in our discussion

board$)$:

a$)$ How can you create a file named $-$i$?$ Which techniques do not work, and why do they not

work? How can you remove the file named $-$i$?$

b$)$ Explain the following error message. Which filenames would a subsequent ls display?

$ ls

abc abd abe abf abg abh

$ rm abc ab$*$

rm: cannot remove 'abc': No such file or directory

c$)$ Explain the error messages displayed in the following sequence of commands:

$ ls $-$l

total $1$

drwxrwxr$-$x $2$ max pubs $10242010-03-0217$:$57$ dirt

$ ls dirt

$ rmdir dirt

rmdir: dirtmp: Directory not empty

$ rm dirt$/*$

rm: No match.

d$)$ Directory permission

i$.$ Make sure you are NOT the $$root$$ user for this exercise. Why?

ii$.$ Create a new directory. What is the default permission for this directory?

iii. Create a new file in the new directory. What is the default permission for this file?

iv$.$ Set the directory permission to $400.$ What does it mean?

v$.$ Set the directory permission to $100.$ What does it mean?

vi$.$ Set the directory permission to $200.$ What does it mean?

e$)$ How to set permissions for the following scenarios?

i$.$ You can modify a file but cannot delete it$.$

ii$.$ You can see the files names $($directory content$)$ but you cannot read their

contents or modify them