LPI 010-160 Linux Essentials Certificate Exam, version 1.6 Exam Dumps and Practice Test Questions Set 6 Q76-90
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Question 76
Which command is used in Linux to view the manual page of another command?
A) help
B) man
C) info
D) doc
Answer: B) man
Explanation
The man command is the primary tool in Linux used to access manual pages for commands, programs, and other utilities installed on the system. Man pages provide detailed documentation about commands and their options, arguments, and usage. This makes man an essential tool for anyone working with Linux, especially when learning new commands or troubleshooting issues.
When you run the man command followed by the name of another command, it displays the manual page for that command. For instance, running man ls will show you the manual page for the ls command, explaining its options and how to use it. Manual pages are structured into several sections, which typically include:
Name: The name of the command and a brief description of what it does.
Synopsis: The syntax for how the command should be used, including the arguments and options it accepts.
Description: A detailed explanation of the command’s functionality.
Options: A list of available options and flags that can modify the behavior of the command.
Examples: Practical examples of how to use the command.
See Also: References to other commands or concepts that are related.
Navigating within a man page is typically done using the keyboard. You can scroll up and down with the arrow keys, search for terms by typing /, and quit the manual page with the q key.
The help command in Linux, on the other hand, provides a brief summary of built-in shell commands (such as cd, echo, etc.) and their options, but it doesn’t offer the extensive documentation found in a man page. It is more limited in scope, typically offering just a quick overview of usage, rather than the full description.
The info command is also used to display documentation, and while it can be very useful, it presents information in a different format, often with hyperlinks and a more detailed structure. Some commands have both a man page and an info page, but info is not as universally used or comprehensive as man pages. The format of info can be harder to navigate, especially for users new to Linux.
The doc command does not exist in standard Linux distributions. The term «doc» may refer to documentation in general, but it is not a command used for accessing command documentation. This is a common misconception or confusion with the man and info commands.
In conclusion, man is the most effective and commonly used command for viewing detailed documentation of Linux commands. It is the go-to tool for understanding how commands work, especially for beginners and administrators who need to refer to command usage frequently.
Question 77
Which command in Linux is used to display a list of currently running processes?
A) ps
B) ls
C) top
D) jobs
Answer: A) ps
Explanation
The ps (process status) command in Linux is used to display information about currently running processes. When you run the ps command, it provides a snapshot of the processes running on the system. This information includes each process’s process ID (PID), the user running the process, the amount of CPU and memory resources each process is consuming, and more.
The output from the ps command will typically show basic details about the processes running under your current session, including their PIDs, the terminal they are running on, the CPU time they’ve used, and the command name. This makes ps a valuable tool for system monitoring and management.
While ps provides a snapshot of the current processes, it is important to note that it is a static command. It shows the state of processes at the exact moment it is run, but it does not update the process list automatically. To view real-time changes in process activity, you would use other tools like top.
One of the most common usages of ps is with the aux flag, which lists all processes running on the system, not just those in the current terminal session. This command shows a comprehensive list of processes, including system and background processes. The ps command is highly customizable, allowing users to filter the output, display additional details, and format the information according to their needs.
The top command is similar to ps, but it is interactive and provides real-time updates. It continuously displays a list of processes, updating every few seconds to show the current system resource usage. This makes top a more dynamic tool for monitoring processes in real time. It’s useful for checking which processes are consuming the most CPU or memory at any given time.
On the other hand, the ls command is used to list the files and directories in the current directory, not processes. While ls can be used to check for the existence of files, it does not provide any information about running processes.
The jobs command lists the jobs that are running in the background in the current shell session. Jobs typically refer to processes started from the terminal, such as scripts or commands run with the & operator to run them in the background. However, jobs does not list all system processes like ps does. It only shows processes that were initiated in the current terminal session.
Thus, while top provides real-time process monitoring, ps is the command to use for getting a snapshot of the current processes running on your system. It’s ideal for checking the status of processes at a specific moment in time.
Question 78
Which of the following commands is used to change the current working directory in Linux?
A) pwd
B) cd
C) mv
D) ls
Answer: B) cd
Explanation
The cd (change directory) command is used to change the current working directory in Linux. The working directory is the directory you are currently in while interacting with the system via the terminal. Using cd, you can navigate between directories within the filesystem.
The cd command allows you to move to any directory by providing its absolute or relative path. For example, if you are in the home directory and want to move to a directory called Documents, you would use the command cd Documents. This would change your current working directory to Documents, allowing you to perform operations within that directory, such as listing files or editing documents.
One of the most useful features of cd is the ability to use special shortcuts:
cd ~ takes you to the home directory of the current user.
cd .. moves you up one directory level, to the parent directory.
cd — switches to the previous directory you were in.
cd / takes you to the root directory of the filesystem.
The pwd (print working directory) command is used to display the absolute path of the current directory you are in. While it helps you identify where you are within the filesystem, it does not allow you to change directories.
The mv command is used to move or rename files. It can be used to change the location of files within the filesystem, but it does not alter your current working directory. For instance, mv file.txt Documents/ will move the file file.txt to the Documents directory, but your terminal session will remain in the directory you were previously in.
The ls command is used to list the files and directories in the current directory. It shows the contents of a directory, but it does not change the directory itself. For example, running ls will list files in the current working directory, but you will remain in the same directory until you use cd to navigate.
Therefore, cd is the correct command for changing the working directory. The other commands (pwd, mv, and ls) serve different purposes, such as displaying the current directory, moving files, and listing directory contents, respectively. The cd command is the only one designed specifically for navigation within the filesystem.
Question 79
Which command is used to display the contents of a file in Linux?
A) cat
B) touch
C) echo
D) ls
Answer: A) cat
Explanation
The cat (concatenate) command in Linux is used to display the contents of a file on the terminal. It is one of the simplest and most commonly used commands for quickly viewing a file’s content without opening it in a text editor.
The basic syntax of the cat command is:
cat [filename]
For example, to display the contents of a file called file.txt, you would run:
cat file.txt
The cat command outputs the entire content of the file to the terminal, allowing you to quickly view its contents. This is particularly useful for smaller files or when you simply need to verify the contents of a file without making any changes to it.
In addition to displaying file contents, cat can also be used to concatenate (combine) multiple files. For instance:
cat file1.txt file2.txt
This will display the contents of both file1.txt and file2.txt in sequence.
However, cat is best suited for smaller files. For larger files, its output can be overwhelming and difficult to navigate because it will dump the entire contents of the file into the terminal window at once. In such cases, it is better to use commands like less or more, which allow you to scroll through the file one page at a time.
The second command, touch, is used to create empty files or update the timestamps of existing files. It does not display any content and is unrelated to viewing files. For example, touch newfile.txt creates an empty file named newfile.txt if it does not already exist, or updates its modification time if it does.
The third command, echo, is used to print text to the terminal or write text to a file. It does not display the contents of files. For example, echo «Hello, world!» will print Hello, world! to the terminal. If used with redirection (echo «Hello» > file.txt), it writes the text to a file.
The fourth command, ls, is used to list the files and directories in the current directory. It does not display the contents of a file; rather, it shows the file names and some details about the files, such as permissions, ownership, and modification date.
Thus, cat is the correct answer for displaying the contents of a file in Linux. While echo, touch, and ls perform different tasks, cat is specifically designed for reading and displaying file content.
Question 80
Which of the following commands is used to display the system’s hostname?
A) hostname
B) uname
C) ifconfig
D) whoami
Answer: A) hostname
Explanation
The hostname command in Linux is used to display or set the hostname of the system. The hostname is a unique name that identifies a computer on a network. It is an important setting in any system as it helps distinguish one device from another in the network.
The basic syntax for the hostname command is simply:
hostname
Running this command without any options will display the current hostname of the system. For example, if your system’s hostname is my-linux, typing hostname will output:
my-linux
The hostname command can also be used to set a new hostname for the system. For example:
sudo hostname new-hostname
This would change the system’s hostname to new-hostname. However, note that changing the hostname typically requires a restart or modification of configuration files to ensure the change persists after reboot.
The second option, uname, provides information about the system’s kernel and architecture but does not specifically display the hostname. For example, uname -a gives detailed information about the system, including the kernel version and machine architecture. However, it will not return the hostname.
The third option, ifconfig, is used to display or configure network interfaces. It shows the IP address, MAC address, and other networking-related details about the system’s network interfaces. While ifconfig can provide information about the system’s network interfaces, it does not display the system’s hostname.
The fourth option, whoami, shows the current user’s username, not the system’s hostname. Running whoami in the terminal will return the username of the currently logged-in user, such as:
Thus, the correct command for displaying the system’s hostname is hostname. The other commands serve different purposes and do not display the hostname directly.
Question 81
Which command in Linux is used to list files and directories in the current directory?
A) ls
B) cp
C) mv
D) rm
Answer: A) ls
Explanation
The ls command in Linux is used to list the files and directories in the current directory. It is one of the most frequently used commands in Linux for basic file management and navigation.
By default, ls will display the names of files and directories in the current directory, excluding hidden files (those whose names start with a dot). For example:
$ ls
Documents Pictures file.txt
This would list three items in the current directory: two directories (Documents and Pictures) and a file (file.txt).
The ls command can be customized with a variety of options:
ls -l displays detailed information, including file permissions, ownership, size, and the last modification time.
ls -a shows all files, including hidden ones (files starting with a dot).
ls -h shows file sizes in a human-readable format, such as 1K, 234M, etc.
ls -R recursively lists all files and directories within the current directory and its subdirectories.
The second option, cp, is used to copy files or directories from one location to another. It does not list files or directories but rather duplicates them. For example, cp file.txt /home/user/ would copy file.txt to /home/user/.
The third option, mv, is used to move or rename files or directories. Like cp, it does not list files but allows users to change the location or name of files. For example, mv file.txt /home/user/ would move file.txt to the /home/user/ directory.
The fourth option, rm, is used to remove files or directories. It is a destructive command and deletes files or directories from the system. For example, rm file.txt would delete the file.txt file. However, it does not list files or directories.
Thus, ls is the correct command for listing files and directories in the current directory. The other commands (cp, mv, and rm) perform file management tasks, such as copying, moving, or deleting files, but they do not list directory contents.
Question 82
Which of the following commands in Linux is used to change the permissions of a file?
A) chmod
B) chown
C) chgrp
D) ls
Answer: A) chmod
Explanation
In Linux, the chmod (change mode) command is used to change the permissions of a file or directory. File permissions in Linux control who can read, write, or execute a file, and chmod allows the user to modify these permissions. The chmod command uses either symbolic or numeric representations to set permissions.
Permissions in Linux are represented by three types of users: the file owner, the group, and others. Each user type can have different permissions:
Read (r): Allows reading the contents of the file.
Write (w): Allows modifying or writing to the file.
Execute (x): Allows running the file as a program (for executable files).
The basic syntax of chmod is:
chmod [permissions] [file]
For example, chmod 755 file.txt will set the file file.txt to be readable, writable, and executable by the owner, and readable and executable by the group and others.
There are two ways to use chmod:
Symbolic notation: Uses letters to represent permissions. For example, chmod u+x file.txt adds execute permission to the file owner (user).
Numeric notation: Uses a three-digit number to represent permissions, where each digit corresponds to the permissions for the user, group, and others. The numeric values are:
4 for read (r)
2 for write (w)
1 for execute (x)
Thus, chmod 755 means:
Owner: read, write, and execute (4+2+1 = 7)
Group: read and execute (4+1 = 5)
Others: read and execute (4+1 = 5)
The second option, chown, is used to change the ownership of a file or directory. It allows the user to change the owner and/or group associated with a file. For example, chown user:group file.txt changes the ownership of file.txt to the specified user and group. While ownership can affect access to files, chown does not change the file’s permissions, which is the role of chmod.
The third option, chgrp, is used to change the group ownership of a file or directory. It modifies the group that has ownership of the file but does not affect the owner or the file’s permissions. For instance, chgrp group file.txt would change the group ownership of file.txt to the specified group, but the file’s permissions remain unchanged.
The fourth option, ls, is used to list the contents of a directory and does not alter file permissions. Running ls shows files and directories, but it does not modify them. To view permissions, you can use the -l flag with ls, which shows a long listing of files, including their permissions.
Therefore, chmod is the correct command for changing file permissions in Linux, while chown and chgrp are used for changing ownership and group ownership, respectively.
Question 83
Which command is used to display the manual pages for a command in Linux?
A) man
B) help
C) info
D) guide
Answer: A) manExplanation
The man command in Linux is used to display manual pages (man pages) for other commands, providing users with detailed documentation on how a command works, its syntax, available options, and examples. The manual pages are a vital resource for understanding how to use different utilities, tools, and commands available on the system.
The basic syntax for using man is:
man [command]
For instance, if you want to read the manual for the ls command, you would use:
man ls
This will open the manual page for ls, providing detailed information about the command’s usage, options, and features. You can navigate through the man page using the arrow keys, and press q to exit and return to the command prompt.
Man pages are structured into sections:
NAME: The name of the command or utility and a brief description.
SYNOPSIS: The syntax for how to use the command, including all available options.
DESCRIPTION: A detailed explanation of the command and its behavior.
OPTIONS: A list of command-line options or flags that modify the command’s behavior.
SEE ALSO: References to related commands or files.
Man pages are an essential resource for users, especially when learning new commands or trying to figure out how to use a particular option or flag with a command. man is thus the most commonly used command for accessing help documentation in Linux.
The second option, help, is often used to display basic help for shell built-in commands or basic information about specific programs. However, it typically provides less detailed information compared to man pages. For example, running help cd will show a brief summary of how the cd command works, but it won’t provide the level of detail found in a man page.
The third option, info, is another command that provides detailed documentation for commands, but it uses a different format than man pages. info is more interactive, and its pages are structured more like hypertext, allowing you to follow links to related sections. While info is useful for some commands, not all utilities have corresponding info pages, and the format can sometimes be more difficult to navigate than the more linear man pages.
The fourth option, guide, is not a standard Linux command. While the term «guide» might refer to documentation or tutorials, there is no guide command in Linux used to display manual pages.
In conclusion, man is the correct command for viewing the manual pages of commands in Linux. While help and info are also used for accessing help, man provides the most comprehensive and widely used documentation.
Question 84
Which command is used to search for a specific pattern in a file?
A) find
B) grep
C) locate
D) search
Answer: B) grep
Explanation
The grep (Global Regular Expression Print) command is used in Linux to search for a specific pattern within one or more files. It is one of the most powerful and widely used tools for pattern matching, especially when working with large text files or output from other commands.
The basic syntax of the grep command is:
grep [pattern] [file]
For example, to search for the word «error» in a file called log.txt, you would use:
grep «error» log.txt
This command will print all lines in log.txt that contain the word «error». You can also use regular expressions to search for more complex patterns.
grep is case-sensitive by default, but you can use the -i option to make the search case-insensitive. For example, grep -i «error» log.txt will match «Error», «ERROR», and «error».
The grep command can also be used with various options:
-r or -R to search recursively through directories.
-l to display only the names of files containing the pattern.
-n to display the line numbers where the pattern is found.
-v to invert the match, displaying lines that do not contain the pattern.
The first option, find, is used to search for files within a directory hierarchy, not to search for patterns inside files. It allows users to search for files by name, size, type, and other attributes. For example, find /home/user -name «*.txt» searches for all .txt files in the /home/user directory.
The third option, locate, is used to quickly find files by name, using a pre-built database of file paths. While it is very fast, it only works with files that are indexed in the locate database. It is not designed to search for patterns within the contents of files. For example, locate file.txt will find all instances of file.txt on the system, but it cannot search the contents of those files.
The fourth option, search, is not a standard Linux command. While the word «search» may be used informally, there is no search command in Linux specifically designed to find patterns in files.
Therefore, grep is the correct command to search for specific patterns within files. It is an essential tool for anyone working with text-based files or logs, as it allows for highly flexible and efficient searching.
Question 85
Which of the following commands in Linux is used to remove a file?
A) rm
B) mv
C) cp
D) touch
Answer: A) rm
Explanation
The rm command in Linux is used to remove (delete) files or directories from the system. This is one of the most commonly used commands for file management, especially when cleaning up or deleting unnecessary files. Once a file is removed with rm, it cannot be easily recovered (unless special recovery tools are used), so it is important to use this command with caution.
The basic syntax of the rm command is:
rm [file]
For example, to delete a file called file.txt, you would use the command:
rm file.txt
This command will remove the file file.txt from the system. It is important to note that rm does not move files to the trash or recycle bin. Once deleted, the file is permanently removed, and space is freed up on the disk.
There are several options that can be used with rm:
rm -r is used to remove directories and their contents recursively. For example, rm -r directory_name will delete the specified directory and all the files and subdirectories inside it.
rm -f forces the deletion of files, even if they are write-protected. This can be useful when removing files that are otherwise locked or protected, but it should be used with caution to avoid accidental deletions.
rm -i prompts the user for confirmation before deleting each file, which provides a safeguard to prevent accidental file deletions.
While rm is useful for removing files, it should be used carefully because there is no easy way to recover a file once it has been deleted. It is important to double-check the file names and directories before running the command.
The second option, mv, is used to move or rename files or directories. For example, mv file.txt /home/user/ will move file.txt to the /home/user/ directory, and mv file.txt newname.txt will rename file.txt to newname.txt. However, mv does not remove files; it only moves or renames them.
The third option, cp, is used to copy files or directories. For instance, cp file.txt /home/user/ will create a copy of file.txt in the /home/user/ directory. Like mv, cp does not remove the original file; it duplicates it.
The fourth option, touch, is used to create new empty files or update the timestamp of existing files. It does not delete files, and in fact, it only modifies the access and modification times of files without changing their contents.
Therefore, rm is the correct command for deleting files and directories in Linux, while the other commands serve different purposes such as moving, copying, or creating files.
Question 86
Which command in Linux is used to display the current working directory?
A) cd
B) ls
C) pwd
D) mkdir
Answer: C) pwd
Explanation
The pwd (print working directory) command in Linux is used to display the current working directory. The working directory is the directory you are currently in while using the terminal or shell. When you run pwd, it outputs the absolute path of the current directory, which is crucial for knowing your location within the filesystem.
The syntax for the pwd command is very simple:
pwd
For example, if you are in the /home/user/Documents directory, running pwd will return:
/home/user/Documents
This tells you exactly where you are in the filesystem hierarchy. The output of pwd is always an absolute path, starting from the root (/) directory and including all the parent directories leading to the current directory.
Knowing the current working directory is essential when navigating the filesystem, especially when running commands that operate on files or directories. By confirming your current directory with pwd, you can ensure that you are working in the correct location before making any changes, such as moving or deleting files.
The first option, cd, is used to change the working directory. For example, running cd Documents will change the current directory to Documents. However, cd does not display the current directory; it only changes it. To view the new directory after running cd, you would typically use pwd.
The second option, ls, is used to list the contents of the current directory. It shows the files and directories in the current working directory but does not tell you where you are within the filesystem. For instance, running ls will display the files in the directory, but it does not show the directory’s path.
The fourth option, mkdir, is used to create a new directory. It allows you to create directories but does not display the current working directory. For example, mkdir new_directory will create a directory named new_directory in the current directory, but you would still need to use pwd to see where you are.
Thus, pwd is the correct command to display the current working directory. The other commands (cd, ls, and mkdir) serve different purposes, such as changing directories, listing contents, and creating directories, but they do not display the current directory.
Question 87
Which command in Linux is used to create a new directory?
A) ls
B) rm
C) mkdir
D) touch
Answer: C) mkdir
Explanation
The mkdir (make directory) command in Linux is used to create new directories. This is one of the most basic commands for organizing files in a filesystem. By using mkdir, users can create directories to organize their files, whether they are working on projects, logs, or data.
The basic syntax of the mkdir command is:
mkdir [directory_name]
For example, to create a directory called new_folder in the current directory, you would use:
mkdir new_folder
After running this command, a new directory called new_folder will be created, and you can now move files into it or create additional files and subdirectories inside it.
The mkdir command also supports several useful options:
mkdir -p allows you to create parent directories as needed. For example, mkdir -p /home/user/Documents/new_folder will create Documents and new_folder if they don’t already exist.
mkdir -v will show a message for each directory that is created, providing confirmation of the action.
The first option, ls, is used to list files and directories in the current directory. It does not create directories or modify the filesystem in any way. Instead, ls helps you see the contents of the directory.
The second option, rm, is used to remove files and directories. It is the opposite of mkdir in that it deletes files and directories. For example, rm -r folder_name will delete the directory folder_name and all its contents, but it does not create new directories.
The fourth option, touch, is used to create empty files or update the timestamp of existing files. For example, running touch file.txt will create an empty file named file.txt if it doesn’t already exist. However, touch does not create directories, and its purpose is quite different from mkdir.
Thus, mkdir is the correct command for creating new directories in Linux. The other commands (ls, rm, and touch) perform different functions, such as listing files, removing files, and creating files, but they do not create directories.
Question 88
Which command is used to view the list of currently running processes in Linux?
A) top
B) ps
C) ls
D) netstat
Answer: B) ps
Explanation
The ps (process status) command is used in Linux to view a list of currently running processes. It provides information about the processes currently being executed by the system, including process IDs (PIDs), memory usage, CPU usage, and more. This is one of the most fundamental commands for system monitoring and is often used by administrators to track which processes are consuming system resources.
By default, the ps command displays processes running in the current shell session. It shows details such as the process ID (PID), the terminal from which the process was initiated, the CPU and memory usage, and the command that started the process.
For example, the ps command can be used to monitor which processes are running and their status. You can run ps to get an overview of your processes and their resource consumption at any given moment.
The ps command can be used in combination with various options to show more comprehensive information. A common variation is ps aux, which displays all the running processes on the system, regardless of the terminal session. This command provides a more detailed list, including the user who owns each process, the percentage of CPU and memory usage, and the command that initiated the process.
Although ps is helpful for getting a snapshot of process statuses, it doesn’t provide real-time updates. For real-time monitoring of processes, the top command is more suitable. While both commands show process information, ps provides a static snapshot, and top offers a dynamic view that is continuously updated.
The second option, top, is also used to view processes, but it continuously updates the list of running processes and their resource usage. top is useful for real-time monitoring, especially when troubleshooting system performance issues or identifying resource-hogging processes.
The third option, ls, is used to list files and directories in a directory. It is a command for exploring and navigating the filesystem, not for monitoring processes. While ls can show file details like size and permissions, it does not display information about running processes.
The fourth option, netstat, is used for viewing network connections and statistics. It provides information about open network ports and active connections, but it does not give details about the system’s processes. netstat is useful for troubleshooting network issues but is not relevant to monitoring running processes.
Therefore, ps is the correct command for viewing currently running processes in Linux. It allows you to get a snapshot of the processes running on your system and analyze their resource usage. Other commands like top, ls, and netstat serve different purposes and do not provide the same information as ps.
Question 89
Which command in Linux is used to display disk space usage?
A) df
B) du
C) ls
D) fdisk
Answer: A) df
Explanation
The df (disk free) command in Linux is used to display information about disk space usage on the system’s mounted filesystems. It shows the amount of total disk space, the used space, the available space, and the filesystem’s mount points. This command is essential for monitoring disk usage and ensuring that your system does not run out of storage.
By default, df gives an overview of the total disk usage for all mounted filesystems, showing how much space is used and how much is still available. The output includes the filesystem name, total disk space, used space, available space, and the percentage of space used.
You can use the df command to quickly identify which partitions or filesystems are running low on space, which is especially useful in situations where disk space is critical for system performance or stability. Additionally, df can be combined with various options to tailor the information to specific needs. For example, using the -h option with df will display the disk space in a human-readable format, using units like KB, MB, GB, etc.
While df shows disk space usage for the entire filesystem, the du (disk usage) command is used to show disk usage for specific files or directories. The du command provides a more granular view of disk usage, allowing users to track the storage consumption of individual files and directories. However, du is not as suitable for checking overall disk space across filesystems, which is where df excels.
The ls command is used to list files and directories in a directory. It shows information about the contents of a directory but does not provide disk space usage details. While ls can show the size of individual files, it does not give an overview of disk space usage for the entire system.
The fdisk command is used to manage disk partitions. It allows users to create, delete, and modify partitions on a disk. However, it does not provide information about disk space usage. fdisk is essential for disk partitioning tasks but is not intended for monitoring disk space.
Therefore, df is the correct command for displaying disk space usage in Linux. It provides a high-level overview of the system’s storage usage and is an important tool for system administrators to monitor disk space and avoid storage-related issues.
Question 90
Which of the following commands in Linux is used to view system resource usage, such as CPU, memory, and process information?
A) top
B) ps
C) uptime
D) free
Answer: A) top
Explanation
The top command in Linux is used to display real-time information about system resources, including CPU usage, memory usage, and process information. It provides a continuously updating view of system activity, which is extremely helpful for monitoring system performance, troubleshooting, and identifying resource-heavy processes.
When you run top, the command outputs a constantly refreshed view of system performance, including:
CPU usage: Displays the percentage of CPU resources consumed by processes, broken down into user, system, and idle times.
Memory usage: Shows how much memory is being used by the system and by specific processes.
Processes: Lists processes running on the system, along with detailed information such as their process IDs (PIDs), user, CPU usage, memory usage, and the command associated with each process.
This real-time monitoring makes top an invaluable tool for system administrators and users who need to identify performance bottlenecks, process hogs, or unexpected spikes in resource usage. It is especially useful for observing how system resources are being allocated over time and for pinpointing processes that may be affecting system stability.
While top provides a dynamic view of system resources, the ps command gives a static snapshot of processes running on the system at a specific moment. You can use ps to check processes, but it doesn’t continuously update like top. For example, running ps aux will show a one-time list of all processes and their resource usage, but it doesn’t provide ongoing monitoring.
The third option, uptime, shows the system’s uptime (how long the system has been running since the last reboot) and the system’s load averages for the past 1, 5, and 15 minutes. While this information is useful for understanding system performance trends, it does not provide detailed information about CPU, memory, or process usage.
The fourth option, free, is used to display information about the system’s memory usage, including the total amount of memory, the amount used, and the amount free. While free provides valuable memory-related information, it does not offer a complete overview of system resources like top, which includes CPU and process data as well.
Therefore, top is the correct command for viewing system resource usage, as it provides a dynamic, real-time display of CPU, memory, and process data, making it an essential tool for system monitoring and troubleshooting. The other commands—ps, uptime, and free—provide useful but less comprehensive information about system resources.