This command will prompt you to remove Joe ' s tmp files that are 3 days older. When the -ok option is used with the find command it causes find to execute the rm command once for each /tmp file that is 3 days older. {} can be used as a filename placeholder.

The -ok option with the find command is used to execute a command once for each file that matches the given criteria. This is commonly used in situations such as removing files or renaming files to have a certain extension. The -ok option causes find to ask for each file before removing it.

What is the find command?

The find command is a versatile method for locating files on a file system. The syntax for this command is as follows:

find < start directory > - < criteria >

Some of the important criteria are described in the table below:

What are some numeric criteria that the find command uses?

The find command can search your system for files that comply with certain numeric criteria. For

example, -ctime, -atime, -

cmin, -amin, etc. The -ctime and -atime are measured in days and the -cmin and -amin are measures in minutes.

For example:

find /tmp -ctime +10

This command searches for files that are more than 10 days older.

find /tmp -cmin +10

This command searches for files that are more than 10 minutes older.

What is the purpose of using \; at the end of the find command?

The purpose of using \; at the end of the find command is that when find is used with -exec and –ok the find command uses ; as the delimiting character. Unfortunately ; is also a delimiting character for the bash shell so we must prevent bash from interpreting it. When a character is preceded with a backslash (\), bash instructs it literally, so typing \; at the bash command prompt will send ; to find command after bash has done its interpretation.

Answer option A is incorrect. This command will prompt you to remove Joe ' s tmp files that are 3 minutes older.

Answer options D and B are incorrect. These are the incorrect command syntaxes.

The ps2pdf utility is used to create PDF files. Therefore, in the above scenario, you will use ps2pdf command to accomplish the task.

Answer option C is incorrect. The pdf2ps utility converts PDF files to PostScript.

Answer options B and D are incorrect. enscript and a2ps commands convert text to PostScript and send it to the print queue.

The Unix utility sed (stream editor) is a text editing tool that can be used to edit text files without having to open them. This utility parses text files and implements a programming language which can apply textual transformations to such files.

It reads input files line by line

(sequentially), applying the operation which has been specified via the command line (or a sed script), and then outputs the line.

Answer option D is incorrect. The more command is used to view (but not modify) the contents of a text file on the terminal screen at a time.

The syntax of the more command is as follows: more [options] file_name

Where,

Answer option A is incorrect. The less command is used to view (but not change) the contents of a text file, one screen at a time. It is similar to the more command. However, it has the extended capability of allowing both forward and backward navigation through the file. Unlike most Unix text editors/viewers, less does not need to read the entire file before starting; therefore, it has faster load times with large files.

The command syntax of the less command is as follows: less [options] file_name

Where,

Answer option C is incorrect. The vi editor is an interactive, cryptic, and screen-based text editor used to create and edit a file. It operates in either Input mode or Command mode. In Input mode, the vi editor accepts a keystroke as text and displays it on the screen, whereas in Command mode, it interprets keystrokes as commands. As the vi editor is case sensitive, it interprets the same character or characters as different commands, depending upon whether the user enters a lowercase or uppercase character.

When a user starts a new session with vi, he must put the editor in Input mode by pressing the " I " key. If he is not able to see the entered text on the vi editor ' s screen, it means that he has not put the editor in Insert mode. The user must change the editor to Input mode before entering any text so that he can see the text he has entered.

The shutdown -h now, halt -h, and poweroff -h commands can be used to shut down the Red Hat operating system immediately.

Answer option B is incorrect. This is an invalid answer and hence cannot be used to shut down the system.

The cp command in option A will copy file3.txt to the destination /home/john/backup. The source and destination paths have been used correctly.

In option D ~ refers to home directory so it is also the correct destination path.

In option B appending / to the destination just tells the cp command explicitly that you are referring to a directory, not a file.

In Linux, the mount command is used to mount and display disks, partitions, and file systems.

Mounting refers to the process in which the operating system prepares the media to be read.

Note: The swap file system cannot be mounted using the mount command.

Answer option D is incorrect. In Linux, the UMOUNT command is used to unmount a file system from its mount point.

Answer options A and B are incorrect. There are no such commands as attach and detach in Linux.

aspell is a utility that can function as an ispell -a replacement, as an independent spell checker, as a test utility to test out Aspell features, and as a utility for managing dictionaries.

Syntax:

aspell [options]

Some important options used with aspell are as follows:

Answer option B is incorrect. The nice command is used to change the priority of a process in the kernel ' s scheduler. A niceness of -20 is the highest priority and 19 is the lowest priority. The default niceness for processes is inherited from its parent process, usually 0. For example, when specifying a very low priority, the following command can be entered: nice -n 19 cc -c *.c &

The above command runs the cc command in the background at a lower priority than the default priority set by the nice command.

Answer options D and A are incorrect. There are no such spell checkers as inspell and spell.

The following options may be used with the aspell command to control which dictionaries to use and how they behave:

The pwd command-line utility is used to display the current working directory.

What is the pwd command?

The pwd command prints the complete pathname of the current working directory to the standard output.

pwd [ -L | -P]

The options are described as follows:

OptionDescription

-LDisplays the logical current working directory.

-PDisplays the physical current working directory.

If no options are specified, the -L option is assumed.

Answer option A is incorrect. The ls command lists the contents of the current directory or the specified directory.

Answer option D is incorrect. The cd command with no argument is used to move to your home directory.

Answer option C is incorrect. The mv command is used to move and/or rename files and directories.

The :q! command is used to quit from the VI editor without saving.

What is VI?

The VI is a visual interactive text editor that allows a user to create, modify, and store files on a Linux computer. It works in the following modes:

Command: This is the default mode of the command. Various commands can be used in this mode to manipulate the opened text.

Input: In this mode, a user can insert text directly in the text screen area.

Answer option D is incorrect. The :w command is used to write the file.

Answer option C is incorrect. The zz command is used to save the file and quit. This is the easiest way to leave the editor, with only two keystrokes.

Answer option B is incorrect. The :q command is used to quit after saving the file.