RHEL 9 RH124 - Chapter 5 - Create, View, and Edit Text Files (Exam Notes)

If I wanted to discard error messages, what would I redirect the error message to? a. /dev/null b. /null c. /etc/null d. /bin/null

/dev/null Explanation: To discard error messages and other output, you can redirect it to '/dev/null'. '/dev/null' is a special device file on Unix-like operating systems that discards all data written to it. Example: command 2> /dev/null This redirects the standard error (stderr) output of the command to '/dev/null', effectively discarding error messages.

If I wanted to redirect the standard error message (if any) to a file, which command would I use? a. 2> file b. 1> file c. 2< file d. 2!< file

2> file Explanation: The correct command to redirect the standard error (stderr) to a file is: command 2> file This redirects the standard error output of the 'command' to the specified file. The '2>' indicates that it's the standard error stream being redirected.

What character would you press to enter extended command mode in vim?

: Explanation: The : keystroke begins extended command mode for tasks such as writing the file (to save it) and quitting the Vim editor.

If I wanted to quit vim without saving changes, what character(s) would I enter in extended command mode?

:q! Explanation: The :q! command quits Vim, and discards all file changes since the last write.

Match the following: - channel 0 - channel 1 - channel 2 ...with: a. Standard input b. Standard output c. Standard error

Channel 0 - Standard input Channel 1 - Standard output Channel 2 - Standard error Explanation: Channel 0 - stdin - Standard input - Keyboard - Read only Channel 1 - stdout - Standard output - Terminal - Write only Channel 2 - stderr - Standard error - Terminal - Write only

What are the four operating modes of vim? a. command mode b. visual edit mode c. version mode d. extended command mode e. edit mode

Command mode, visual edit mode, extended command mode, and edit mode Explanation: The Vim editor offers various modes of operation such as command mode, extended command mode, edit mode, and visual mode. As a Vim user, always verify the current mode, because the effect of keystrokes varies between modes.

You want to create a shell variable. You want the name of the variable to be DAY and you want it equal to 7. What would you enter in the shell window?

DAY=7 Explanation: This sets the variable DAY to the value 7. You can then use the variable in your shell scripts or commands.

If I wanted to know how many characters are in the /etc/passwd file, what command, option, and argument would I use? Hint: You will use the cat, wc, and the pipe command.

cat /etc/passwd | wc -c OR cat/etc/passwd | wc -m Explanation: To find out how many characters are in the /etc/passwd file, you can use the cat command to display the contents of the file, the wc command with the -c (or -m) option to count characters, and the pipe (|) command to connect them. - 'cat /etc/passwd': Displays the contents of /etc/passwd. - '|': The pipe redirects the output of cat to the input of wc. - wc -c: Counts the number of bytes in the input. ('wc -m': Counts the number of characters in the input.) The commands wc -c and wc -m would give the same output because they both count characters. - 'wc -c': Counts the number of bytes in the input. In many character encodings, especially in systems like Unix/Linux where UTF-8 is common, one byte represents one character. So, the count of bytes is effectively the count of characters. - 'wc -m': Counts the number of characters in the input. In some systems or character encodings where characters may be represented by multiple bytes (as in UTF-16 or UTF-32), the count of characters may differ from the count of bytes. However, in systems where one byte represents one character (like UTF-8), wc -m would be equivalent to wc -c. However, if you were dealing with a different character encoding, there might be a difference between the two options.

What is the default mode when starting vim?

command mode Explanation: When you first open Vim, it starts in command mode, which is used for navigation, cut and paste, and other text modification.

If I wanted to redirect the output of a command to a new file, which command would I use? a. echo "my data" > file b. echo "my data" >> file c. echo "my data" <> file d. echo "my data" >! file

echo "my data" > file Explanation: This command will create a new file named "file" and write the output of the echo command ("my data") to that file, overwriting its contents if the file already exists. The '>' symbol in a command is a redirection operator in Unix-like operating systems, including Linux. It is used to redirect the output of a command to a file.

If I wanted to redirect the output of a command to a file and append the data, which command would I use? a. echo "my data" >> file b. echo "my data" > file c. echo "my data" << file d. echo "my data" < file

echo "my data" >> file Explanation: This command uses the '>>' symbol, which is the append redirection operator. It appends the output of the 'echo' command to the specified file. If the file doesn't exist, it will be created. If it already exists, the new data will be added to the end of the file without overwriting its existing content.

You created a shell variable WEEK and set the variable content to 8. Now, you want to display the content of the WEEK variable. What command would you enter?

echo $WEEK Explanation: To display the content of the WEEK variable, you would use the 'echo' command. The dollar sign ($) is used to reference the value of a variable in Bash.

What command, options, and arguments would I enter to redirect the first 20 lines the passwd file located in /etc to a file in /home/student/Documents/passwd.txt

head -n 20 /etc/passwd > /home/student/Documents/passwd.txt Explanation: You can use the head command to extract the first 20 lines of the /etc/passwd file and then redirect that output to a file. - 'head': Command to display the beginning of a file. - '-n 20': Option to specify the number of lines to display (in this case, the first 20 lines). - '/etc/passwd': Path to the input file (the /etc/passwd file). - '> /home/student/Documents/passwd.txt': Redirects the output to the specified file (/home/student/Documents/passwd.txt). The > operator overwrites the file if it already exists or creates a new one if it doesn't.

What character would you press to enter insert mode in vim?

i Explanation: An i keystroke enters insert mode, where all typed text becomes file content. Pressing Esc returns to command mode.

If I wanted to pipe the results of the ls command to the more command, which command would I run?

ls | more Explanation: This command uses the pipe (|) symbol to redirect the standard output of the 'ls' command to the standard input of the more command. As a result, you can view the output of 'ls' one screen at a time using the 'more' pager.

If you wanted to see all the shell variables, what command would you enter at the prompt? a. set b. see c. show d. show var

set Explanation: The 'set' command displays all environment variables and shell variables, including their values.

Which command copies its standard input to its standard output and also redirects its standard output to the files named as arguments to the command when piping.

tee Explanation: The tee command reads from standard input and writes to standard output and files simultaneously. It's commonly used in conjunction with pipes (|) to capture and display the output while also saving it to one or more files. Example: command | tee file1.txt file2.txt This command will run 'command', take its output, display it on the terminal, and write it to both file1.txt and file2.txt.

What character or symbol is called the pipe character?

| Explanation: Pipeline - A sequence of one or more commands that are separated by the vertical bar character ( | ). The pipe character is used to connect the standard output of the first command to the standard input of the next command. This allows for the creation of command pipelines, where the output of one command becomes the input for another, facilitating powerful and flexible command-line operations.