Codecademy Terminal Commands

Question 1

>

Answer 1

$ cat oceans.txt > continents.txt

takes the standard output of the command on the left, and redirects it to the file on the right.

Question 2

>

Answer 2

$ cat oceans.txt > continents.txt

takes the standard output of the command on the left, and redirects it to the file on the right.

Question 3

> >

Answer 3

$ cat glaciers.txt&raquo_space; rivers.txt

> > takes the standard output of the command on the left and appends (adds) it to the file on the right.

Question 4

|

Answer 4

$ cat volcanoes.txt | wc

is a “pipe”. The | takes the standard output of the command on the left, and pipes it as standard input to the command on the right. You can think of this as “command to command” redirection.

Question 5

~/.bash_profile

Answer 5

$ nano ~/.bash_profile

~/.bash_profile is the name of file used to store environment settings. It is commonly called the “bash profile”. When a session starts, it will load the contents of the bash profile before executing commands.

Question 6

alias

Answer 6

alias pd=”pwd”

The alias command allows you to create keyboard shortcuts, or aliases, for commonly used commands.

Answer 7

$ cat < lakes.txt

< takes the standard input from the file on the right and inputs it into the program on the left.

Question 8

|

Answer 8

$ cat volcanoes.txt | wc

is a “pipe”. The | takes the standard output of the command on the left, and pipes it as standard input to the command on the right. You can think of this as “command to command” redirection.

Question 9

~/.BASH_PROFILE

Answer 9

$ nano ~/.bash_profile

~/.bash_profile is the name of file used to store environment settings. It is commonly called the “bash profile”. When a session starts, it will load the contents of the bash profile before executing commands.

Question 10

ALIAS

Answer 10

alias pd=”pwd”

The alias command allows you to create keyboard shortcuts, or aliases, for commonly used commands.

Question 11

env | grep VARIABLE

Answer 11

env | grep PATH

env | grep PATH is a command that displays the value of a single environment variable.

Question 12

cp

Answer 12

$ cp ada_lovelace.txt historical/

cp copies files or directories. Here, we copy the file ada_lovelace.txt and place it in the historical/ directory

Question 13

*

Answer 13

$ cp * satire/

The wildcard * selects all of the files in the current directory. The above example will copy all of the files in the current directory to the directory called satire. There are other types of wildcards, too, which are beyond the scope of this glossary.

$ cp m*.txt scifi/

Here, m*.txt selects all files in the working directory starting with “m” and ending with “.txt”, and copies them to scifi/.

Question 14

env

Answer 14

The env command stands for “environment”, and returns a list of the environment variables for the current user.

Question 15

ENV | GREP VARIABLE

Answer 15

env | grep PATH

env | grep PATH is a command that displays the value of a single environment variable.

Question 16

export

Answer 16

export USER=”Jane Doe”

export makes the variable to be available to all child sessions initiated from the session you are in. This is a way to make the variable persist across programs.

Question 17

grep

Answer 17

$ grep “Mount” mountains.txt

grep stands for “global regular expression print”. It searches files for lines that match a pattern and returns the results. It is case sensitive.

Question 18

grep -i

Answer 18

$ grep -i “Mount” mountains.txt

grep -i enables the command to be case insensitive.

Question 19

grep -R

Answer 19

$ grep -R Arctic /home/ccuser/workspace/geography

grep -R searches all files in a directory and outputs filenames and lines containing matched results. -R stands for “recursive”.

Question 20

grep -Rl

Answer 20

grep -Rl Arctic /home/ccuser/workspace/geography

grep -Rl searches all files in a directory and outputs only filenames with matched results. -R stands for “recursive” and l stands for “files with matches”.

Question 21

HOME

Answer 21

$ echo $HOME

The HOME variable is an environment variable that displays the path of the home directory.

Question 22

ls

Answer 22

$ ls
2014 2015 hardware.txt

ls lists all files and directories in the working directory

Question 23

ls -a

Answer 23

ls -a
. .. .preferences action drama comedy genres.xt

ls -a lists all contents in the working directory, including hidden files and directories

Question 24

ls -l

Answer 24

ls -l
drwxr-xr-x 5 cc eng 4096 Jun 24 16:51 action
drwxr-xr-x 4 cc eng 4096 Jun 24 16:51 comedy
drwxr-xr-x 6 cc eng 4096 Jun 24 16:51 drama
-rw-r–r– 1 cc eng 0 Jun 24 16:51 genres.txt

ls -l lists all contents of a directory in long format.

Question 25

ls -t

Answer 25

ls -t orders files and directories by the time they were last modified.

Question 26

pwd

Answer 26

$ pwd
/home/ccuser/workspace/blog

pwd prints the name of the working directory

Question 27

mv

Answer 27

$ mv superman.txt superhero/

To move a file into a directory, use mv with the source file as the first argument and the destination directory as the second argument. Here we move superman.txt into superhero/.

Question 28

nano

Answer 28

$ nano hello.txt

nano is a command line text editor. It works just like a desktop text editor like TextEdit or Notepad, except that it is accessible from the the command line and only accepts keyboard input.

Question 29

PATH

Answer 29

$ echo $PATH

/home/ccuser/.gem/ruby/2.0.0/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin

PATH is an environment variable that stores a list of directories separated by a colon. Each directory contains scripts for the command line to execute. PATH lists which directories contain scripts.

Question 30

pwd

Answer 30

$ pwd
/home/ccuser/workspace/blog

pwd prints the name of the working directory

Question 31

rm

Answer 31

$ rm waterboy.txt

rm deletes files. Here we remove the file waterboy.txt from the file system.

Question 32

rm -r

Answer 32

$ rm -r comedy

rm -r deletes a directory and all of its child directories.

Question 33

sed

Answer 33

$ sed ‘s/snow/rain/’ forests.txt

sed stands for “stream editor”. It accepts standard input and modifies it based on an expression, before displaying it as output data.

In the expression ‘s/snow/rain/’:

s: stands for “substitution”.
snow: the search string, the text to find.
rain: the replacement string, the text to add in place.

Question 34

sort

Answer 34

$ sort lakes.txt

sort takes a filename or standard input and orders each line alphabetically, printing it to standard output.

Question 35

standard error

Answer 35

standard error, abbreviated as stderr, is an error message outputted by a failed process.

Question 36

uniq

Answer 36

$ uniq lakes.txt

uniq, short for “unique”, takes a filename or standard input and prints out every line, removing any exact duplicates.

Question 37

stdin

Answer 37

standard input, abbreviated as stdin, is information inputted into the terminal through the keyboard or input device.

Question 38

stdout

Answer 38

standard output, abbreviated as stdout, is the information outputted after a process is run.

Question 39

touch

Answer 39

$ touch data.txt

touch creates a new file inside the working directory. It takes in a file name as an argument, and then creates a new empty file in the current working directory. Here we used touch to create a new file named keyboard.txt inside the 2014/dec/ directory.

If the file exists, touch is used to update the modification time of the file

Question 40

uniq

Answer 40

$ uniq lakes.txt

uniq, short for “unique”, takes a filename or standard input and prints out every line, removing any exact duplicates.

Question 41

cat

Answer 41

The most common use of cat is to read the contents of files, and cat is often the most convenient program for this purpose. All that is necessary to open a text file for viewing on the display monitor is to type the word cat followed by a space and the name of the file and then press the ENTER key. For example, the following will display the contents of a file named file1:

cat file1