Linux Essentials 2.21 - Working with Text M10 Exam

Error messages generated by commands are sent where by default?

• STDERR

• STDIN

• STDOUT

• Log files

Answer explanation

By default, error messages generated by commands are sent to STDERR (standard error). This is a separate output stream from STDOUT (standard output), which is used for regular output.

A successful command may, or may not, print output to STDOUT. True or False?

• True

• False

Answer explanation

True. A successful command can execute without producing output to STDOUT, depending on its purpose. For example, commands that modify files or settings may not need to display any output.

Which of the following commands will direct error messages to the file error.log?

• ls /root > error.log

• ls /root >> error.log

• ls /root $> error.log

• ls /root 2> error.log

Answer explanation

The command 'ls /root 2> error.log' redirects error messages (file descriptor 2) to the file error.log. The other options either redirect standard output or are incorrectly formatted.

A pipe allows you to…

• Send the output of a command to a file.

• Type multiple commands at one prompt.

• Send the same input to multiple commands.

• Send the output of one command to another.

Answer explanation

A pipe is used in command-line interfaces to send the output of one command directly as input to another command, allowing for efficient data processing and manipulation.

Channel 2 is:

• STDIN

• STDALL

• STDERR

• STDOUT

Answer explanation

Channel 2 refers to STDERR, which is the standard error output stream used for error messages. STDIN is for input, STDOUT is for standard output, and STDALL is not a standard stream.

Which of the following commands will append its output to output.file?

• echo Testing > output.file

• echo Testing >> output.file

• echo Testing -> output.file

• output.file < echo Testing

Answer explanation

The command 'echo Testing >> output.file' appends the output of 'echo Testing' to 'output.file'. The '>>' operator is specifically used for appending, while '>' overwrites the file, making the second option the correct choice.

Which command(s) can be used to sort the lines of list.file alphabetically and display them? (Choose two)

• cat list.file | sort

• echo list.file > sort

• cat list.file >> sort

• sort < list.file

Answer explanation

The commands 'cat list.file | sort' and 'sort < list.file' both read the contents of 'list.file' and sort them alphabetically. The other options do not sort or display the file contents correctly.

Which option of the head command will display only the first five lines of a file?

• -l 5

• No option needed; head displays only five lines by default.

• -n 5

• -n

Answer explanation

The correct option is '-n 5', which explicitly tells the head command to display the first five lines of a file. While head does show the first ten lines by default, '-n 5' is the precise way to limit it to five.

The grep command…

• Displays all lines that begin with the specified Regular Expression.

• Displays all lines in a file containing the specified Regular Expression.

• Displays only the first line that matches the Regular Expression.

• Deletes all lines that match the Regular Expression.

Answer explanation

The grep command searches through files and displays all lines that contain the specified Regular Expression, making the second choice the correct answer. It does not limit to lines that begin with or delete matching lines.

The grep command can be used with glob characters. True or False?

• True

• False

Answer explanation

True. The grep command can indeed be used with glob characters, allowing users to match filenames or patterns in a flexible way. This enhances its functionality in searching through files.