Power of Command Line Pt1

Front

What is the proper command to use to compress the file filename.txt into the zip archive called myfile.zip?

Back

zip myfile.zip filename.txt

Answer explanation

The syntax for zipping a file into a zip archive is "zip myfile.zip filename.txt".

Front

What statement is used to get input from the terminal when a shell script is being run?

Back

read

Answer explanation

The read command is used to get input from the terminal when using a shell script.

Front

Consider the following script:
#!/bin/bash
ip=`route -n | grep UG | tr -s “ “ | cut -f 2 -d “ “`
echo “Checking to see if $ip is up..."
ping -c 5 $ip
What does the script output?

Back

Checking to see if ipaddress is up...

Answer explanation

The line in the script that starts with the echo command will cause the string, "Checking to see if $ip is up…" will be executed. When this is executed, the value of $ip will be replaced with the result of the command in the second line (which contains route).

Front

Which option can be used with tail to print the last 10 lines of a file and then keep printing any new lines that may be added continuously? Options: -n, -f, -x, -a

Back

-f

Answer explanation

The -f option is used to "follow" the contents of the file. This lets tail print the last 10 lines of a file (usually a log file) and continue to print out new lines to the screen as they are added to the file.

Front

Which command is used to make a shell variable known to subsequently executed programs?

Back

export

Answer explanation

The command export is used to make a shell variable known to subsequently executed programs. Essentially, the export command creates a globally accessible variable when it is run.

Front

What option can be used with cat to display line numbers with the text of a file to the screen? Options: #, -x, -n, -1

Back

-n

Answer explanation

The -n option will show the line numbers next to a file's contents when displayed to the screen. For example, "cat -n song.txt" will display the contents of the song.txt file with line numbers down the left column of the display.

Front

What is one of the most basic features of a shell script? Options: The ability to compile programs, The ability to run commands, The ability to ask for user input, The ability to display command output information

Back

The ability to run commands

Answer explanation

A shell script is a computer program designed to be run by the shell. Typical operations performed by shell scripts include file manipulation and command execution. The most basic scripts run commands in serial order and do not provide any output back to the screen or seek input from a user.

Front

Which command creates an archive file, named backup.tar, containing all the files from the directory /home? Options: tar -cf backup.tar /home, tar -cf /home backup.tar, tar -xf /home backup.tar, tar -xf backup.tar /home

Back

tar -cf backup.tar /home

Answer explanation

The tar command allows you to quickly access a collection of files and place them into a highly compressed archive file. The -c option creates a new archive while -f uses the given filename as the archive's filename. Specifying the directory ensures the files to be placed in the archive file come from that folder.

Front

Which command is used to print the first 10 lines of a file to the display? Options: cat, tail, head, less

Back

head

Answer explanation

Head command is the opposite of the tail command. The head command is used to print the first 10 lines of a file. The tail command is used to print the last 10 lines of a file.

Front

Which command displays the value of the HOME variable to the terminal's display? Options: echo HOME, echo $HOME, echo &HOME, echo "HOME"

Back

echo $HOME

Answer explanation

To display the contents of a variable to the terminal's display, the command syntax is echo $VARIABLE, where VARIABLE is the variable's name.