S. No.	Command	Example	Implementation
a.	nohup	nohup find -size +100k > log.txt	Runs a command, making it immune to any HUP (hangup) signals while it is running. Runs the find command, instructing it to search for any file bigger then 100k. Find will continue to search regardless of the user's connection to the terminal, and log results to the file log.txt
b.	last	last	Finds out who has recently logged in and out on your server
c.	more	more file1	Look at file, one page at a time
d.	less	less file1	Less is a program similar to more, but which allows backward movement in the file as well as forward movement.
e.	pg	pg <filename>	pg displays a text file on a CRT one screenful at once. After each page, a prompt is displayed. The user may then either press the newline key to view the next page
f.	history	history	Lists commands you've done recently
g.	touch	touch <filename>	Creates a new file of zero bytes, if does not exist. If, however exists, changes the timestamp of it.
h.	tr	tr [a-z] [A-Z] <filename>	Translates in the file as per given translation. In the example, changes the lowercase characters to uppercase characters.
i.	sed	sed 's/unix/linux/' file.txt	Sed command is mostly used to replace the text in a file. The below simple sed command replaces the word "unix" with "linux" in the file.
j.	emacs	emacs filename	emacs is a screen editor.
k.	du	du <filename>	Lists the disk usage of the given file.
l.	diff	diff <file1> <file2>	Checks whether two files are same or different.

1. Explain the syntax of nohup.
2. How does diff command work?
3. What does history command give as output?
4. What is the difference between tr and sed?
5. Where does the output of the command given with nohup gets stored by default?

-l	Set up for editing LISP programs.
-R	Readonly mode; the readonly flag is set, preventing accidental overwriting of the file.
-r filename	Edit filename after an editor or system crash. (Recovers the version of filename that was in the buffer when the crash occurred.)
-S	This option is used in conjunction with the -t tag option to tell vithat the tags file may not be sorted and that, if the binary search (which relies on a sorted tags file) for tag fails to find it, the much slower linear search should also be done. Since the linear search is slow, users of large tags files should ensure that the tags files are sorted rather than use this flag. Creation of tags files normally produces sorted tags files. See ctags for more information on tags files.
-t tag	Edit the file containing the tag tag, and position the editor at its definition.
-v	Start up in display editing state using vi. You can achieve the same effect by typing the vi command itself.
-V	Verbose mode. When ex commands are read by means ofstandard input, the input will be echoed to standard error. This may be useful when processing ex commands within shell scripts.
-x	Encryption option; when used, vi simulates the X command of exand prompts the user for a key. This key is used to encrypt and decrypt text using the algorithm of the crypt command.
-wn	Set the default window size to n. This is useful when using the editor over a slow speed line.
-C	Encryption option; same as the -x option, except that visimulates the C command of ex. The C command is like the Xcommand of ex, except that all text read in is assumed to have been encrypted.
+command | -c command	Begin editing by executing the specified editor command (usually a search or positioning command).
filename	The file to be edited.

1. Why is vi so popular?
2. What are the various modes of vi editor?

1. What is a shell script? How do we run it?
2. What is the use of chmod command? Explain the options used in it.
3. Why does $0 display the current shell script name?
4. Is the answer same all the time for the same process? Why or why not?

1. Explain the if-else construct.
2. What is the difference between x and $x?
3. What is the difference between ‘’ and “”?
4. What is the need of expr?
5. Explain –ge, -eq, -le, etc?

1. What are the options for checking a directory and a file?
2. How many types of files are there in UNIX? Explain.
3. What is the use of cat in this program?
4. Explain the line w=`cat $1 | wc –w`
5. Explain the du command.
6. How does sort command sorts in reverse order? 

1. What are the syntax of for and while loop?
2. Explain the syntax of expr command for multiplication of two numbers.

1. Pipes – Provides a way for processes to communicate with each another by exchanging messages. Named pipes provide a way for processes running on different computer systems to communicate over the network.
2. Shared Memory – Processes can exchange values in the shared memory. One process will create a portion of memory which other process can access.
3. Message Queue – It is a structured and ordered list of memory segments where processes store or retrieve data.
4. Semaphores – Provides a synchronizing mechanism for processes that are accessing the same resource. No data is passed with a semaphore; it simply coordinates access to shared resources.

1. ipcs –a
2. ipcs –q
3. ipcs –s
4. ipcs –m
5. ipcs -q -i 32768

1. ipcs command with -a option lists all the IPC facilities which has read access for the current process. It provides details about message queue, semaphore and shared memory.
2. ipcs with option -q, lists only message queues for which the current process has read access.
3. ipcs -s option is used to list the accessible semaphores.
4. ipcs -m option with ipcs command lists the shared memories.
5. ipcs -i option provides detailed information about an ipc facility. Option -i with -q provides information about a particular message queue. Option -i with -s provides semaphore details. Option -i with -m provides details about a shared memory.

1. What do you mean by IPC? What are the various categories that lie within it?
2. Explain the various options used with IPCS.