Pass the LPI LPIC Level 1 101-500 Questions and answers with CertsForce

To save a file and exit the vi/vim editor, you need to switch to command mode by pressing the Esc key, then type a colon (:) followed by a command. There are two commands that can save a file and quit the editor: x and wq. The x command writes the buffer to the file only if there are unsaved changes, while the wq command always writes the buffer to the file and updates the file modification time. Both commands are followed by an exclamation mark (!) to force the operation and override any warnings. Therefore, the correct sequences are:

Esc ZZ: This is equivalent to typing :x and hitting Enter.

Esc :wq!: This writes the buffer to the file and quits the editor, ignoring any warnings.

The other options are incorrect because:

Ctrl :w! is not a valid sequence. The Ctrl key does not switch to command mode, and the w command only saves the file without exiting.

Esc zz is not a valid sequence. The zz command does not exist in vi/vim.

Ctrl XX is not a valid sequence. The Ctrl key does not switch to command mode, and the XX command does not exist in vi/vim.

References:

How to Save a File in Vi / Vim Editor & Quit - phoenixNAP

How to Save a File in Vim / Vi and Quit the Editor | Linuxize

How To Save a File in Vi / Vim Text Editor - nixCraft

How to Save a File in Vi / Vim Editor & Quit - GeeksforGeeks

The tee command reads from standard input and writes to both standard output and one or more files1. Therefore, the command myapp | tee file1.log will send the output of the program myapp to both the terminal and the file file1.log. The other commands will either fail to write to both standard output and file, or write the wrong output. For example, the command cat < myapp | cat > file1.log will try to read the file myapp as input and write it to the file file1.log, but it will not display anything on the terminal. The command myapp 0>&1 | cat > file1.log will redirect the standard input of myapp to its standard output, and then pipe it to the file file1.log, but it will not display anything on the terminal. The command myapp | cat > file1.log will pipe the output of myapp to the file file1.log, but it will not display anything on the terminal. The command tee myapp file1.log will try to read from standard input and write to both the file myapp and the file file1.log, but it will not execute the program myapp. References:

[LPI Linux Essentials - 1.3 Basic Editing]

[LPI Linux Essentials - 1.4 I/O Redirection]

[LPI Linux Essentials - 1.5 Manage Simple Partitions and Filesystems]

The tr command is used to translate or delete characters from a given input. The -d option specifies that the characters in the second argument should be deleted from the input. In this case, the second argument is aieou, which are the vowels in the English alphabet. Therefore, the tr command will delete any vowel from the input, which is Hello World. The output will be the input without any vowels, which is Hll Wrld. References:

[LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.7: Perform basic file management, Weight: 4, Key Knowledge Areas: Use of tr to perform basic text transformations.

[LPI Linux Essentials Certification All-in-One Exam Guide], Chapter 5: Working with Files, Page 165, Using the tr Command.

The default nice level when a process is started using the nice command is 10. This means that the process will have a lower priority than the normal processes, which have a nice level of 0. The nice command allows the user to adjust the priority of a process at the time of its execution. The syntax of the nice command is:

nice [-n {nice value increment}] [command]

The -n option specifies the nice value increment, which can be a positive or negative integer in the range of -20 to 19. The command is the name of the program or script to be executed. If the -n option is omitted, the default nice value increment is 10. For example, the following command will run the program ackermann with a nice value of 10:

nice ./ackermann

To verify the nice value of a running process, we can use the ps or top commands and look at the NI column. For example, the following command will show the nice value of the ackermann process:

ps -el | grep ackermann

References:

[How to Set Process Priorities With nice and renice on Linux], Topic: The nice Command.

[Nice and Renice Command in Linux with Examples], Topic: Working with nice and renice Command.

The rmdir command removes an empty directory. To remove a directory whose name contains a backslash, the backslash must be escaped with another backslash. Therefore, the correct command is rmdir ~/\dir. The other commands will either fail to find the directory or interpret the backslash as part of a path name. References:

[LPI Linux Essentials - 1.3 Basic Editing]

[LPI Linux Essentials - 1.4 I/O Redirection]

[LPI Linux Essentials - 1.5 Manage Simple Partitions and Filesystems]

The /etc/mtab file is a system-generated file that lists all the currently mounted devices and their mount options. It is updated automatically by the mount and umount commands. It can be used to check which devices are mounted and where, as well as their filesystem type and mount options. The /etc/mtab file hasthe same format as the /etc/fstab file, which is a user-edited file that lists the devices that should be mounted at boot time or on demand. References:

LPIC-1 Exam 101 Objectives, Topic 101: System Architecture, 101.1 Determine and configure hardware settings, Key Knowledge Areas, The following is a partial list of the used files, terms and utilities: /etc/mtab

LPIC-1 101-500 Exam Prep, Section 1: System Architecture, Lesson 1.1: Determine and Configure Hardware Settings, Video: 1.1.4 Mounting and Unmounting Filesystems, Transcript: The /etc/mtab file is a system-generated file that lists all the currently mounted devices and their mount options.

 The tail command prints the last part of a file to the standard output. The -n option specifies the number of lines to print. Therefore, tail -n 10 filename will print the last 10 lines of the file named filename. The other commands are either invalid or do not perform the desired task. The cat command concatenates files and prints them to the standard output, but it does not have a -n option. The dump command is used to backup filesystems, not to print files. The head command prints the first part of a file, not the last part. References:

LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.3 Perform basic file management

LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The vi command is a text editor that operates in two modes: command mode and insert mode. Command mode is used to enter commands to manipulate the text, such as saving, quitting, copying, pasting, etc. Insert mode is used to enter text into the file. When the vi command is invoked without any additional parameters, it starts in command mode and opens a new empty file. To enter text, the user has to press i to switch to insert mode. To return to command mode, the user has to press Esc. To save and quit, the user has to enter :wq in command mode. The other options are either incorrect or not applicable. The vi command does not load the last file used or the content of the vi buffer by default. It also does not require the user to explicitly create or load a file. It does not exit with an error message unless there is a problem with the terminal or the system. References:

LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.7 Use and edit text files

LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The ? symbol within regular expressions represents an optional match of the preceding qualifier. A qualifier is a character or a group of characters that can be repeated a certain number of times, such as , +, ?, {n}, {n,}, or {n,m}. The ? symbol means that the qualifier can occur zero or one times, but not more. For example, the regular expression colou?r matches both “color” and “colour”, but not “colouur” or “colr”. The ? symbol can also be used to make other qualifiers lazy, meaning that they will match the smallest possible number of characters, instead of the largest (greedy). For example, the regular expression a.?b matches the shortest string that starts with “a” and ends with “b”, such as “ab” or “a-b”, but not “a-b-c”. References:

[LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.7: Perform basic file management, Weight: 4, Key Knowledge Areas: Use of egrep to search for extended regular expressions in text output.

[Regular expression syntax cheat sheet], Topic: Quantifiers.

The export command is a Bash built-in command that exports environment variables and functions for use in other shell sessions1. Environment variables are named values that affect the behavior of applications and processes2. For example, the PATH variable stores a list of directories where executable programs are located, and the LANG variable sets the language and locale of the system2. By using the export command, you can make these variables available to any child process spawned by the current shell1. For example, if you want to set the EDITOR variable to vim for all subshells, you can run:

export EDITOR=vim

The export command can also be used to export functions, which are blocks of code that can be reused by invoking their name3. For example, if you want to create and export a function that prints “Hello world”, you can run:

hello () { echo “Hello world”; } export -f hello

Then, you can call the hello function in any subshell or script that inherits the environment from the current shell.

The other options are not related to the export command. Option A refers to the mount command, which attaches a filesystem to a directory4. Option B refers to the command substitution feature, which runs a command in a subshell and replaces it with its output5. Option C refers to the history command, which displays the command history of the current shell. Option E refers to the exportfs command, which maintains the table of exported NFS shares.

References:

[LPI Linux Essentials - 1.3 Basic Editing]

[LPI Linux Essentials - 1.4 I/O Redirection]

[LPI Linux Essentials - 1.5 Manage Simple Partitions and Filesystems]

Linux export Command with Examples - phoenixNAP

bash - What does "export" do in shell programming? - Stack Overflow

How to Use Export Command in Linux [Explained for Beginners]

mount(8) - Linux manual page

Command Substitution - Bash Reference Manual

[history(3) - Linux manual page]

[exportfs(8) - Linux manual page]