The chmod command changes the access mode of one file or multiple files. The syntax for the chmod command is: chmod [option] mode files. The permission can be set for the user, group and others.

The pwd command display the path of the current directory. The full pathname will look something like this

/home/world/asia/india

In this command, the output of the 'who' command is passed to the 'sort' command, therefore it will print sorted list of users.

The 'x' key deletes a single character in Vi editor.

The /bin directory holds all the executable binary programs (file) required during booting, repairing, files required to run into single-user-mode, and other important, basic commands.

Whenever an 'if' statement is used in Linux, it must be closed using the reverse of 'if', 'fi'.

The tee command executes the given command and stores the standard output of that command into one or more files.

Syntax : tee [OPTION]... [FILE]..

Each Linux user has a unique identification number known as User ID(UID) which is assigned automatically. To change its value, the command 'usermod -u UID username' can be used.

To remove an environmental variable the 'unset' command is used. Usage : unset variablename Example : unset marks

The read statement is used to get input from keyboard and store it to a variable.

The name of a variable cannot contain '?'. The only allowed symbol is underscore ( _ )

-mt is not a valid operator.

The initial value of variable 'i' is 5. The while loop will continue as long as the value of the variable 'i' is not equal to 0. Value of 'i' will be decremented in each iteration. Therefore, the result will be 5 4 3 2 1.

Exit is not a valid AWK variable.

The join command is used to merge the contents of two files. Usage : join file1 file2

The shell is not part of system kernel, but uses the system kernel to execute programs, create files, etc.

Permissions or privileges are not a part of the etc/passwd file.

The cut command is used to extract a vertical selection of columns (character position) or fields from one or more files. The syntax for extracting a selection based on a column number is: $ cut -c n [filename(s)]

The write permission allows the user to write or edit the contents of the file.

Grep is not a communication, but a search command that allows to search one file or multiple files for lines that contain a pattern.

The head command writes the first ten lines of a file to the screen.

Usage : head sample.txt

The ls -a command is used to print the list of all the hidden files. A hidden file in Linux is the one that starts with a dot (.)

SIGBREAK is not a valid process signal in Linux.

The [ ] represents a range of characters. The range operator allows us to limit to a subset of characters.Usage : ls [sv]*

The value of 'x', which is 3, will be printed.