Linux commands

A shell is a program that receives commands from the user and gives it to the OS to process, and it shows the output.

pwd

It gives us the absolute path, which means the path that starts from the root. The root is the base of the Linux file system. It is denoted by a forward slash /

Air-Alena:~ alenaagapova$ pwd
/Users/alenaagapova

ls and ls-a

ls — Use the "ls" command to know what files are in the directory you are in. You can see all the hidden files by using the command “ls -a”.

Air-Alena:~ alenaagapova$ ls
Alena Borodina - QA Engineer.pages	Pictures
Applications				Public
Book.txt				PycharmProjects
Desktop					TestProject
Documents				User.txt



Air-Alena:~ alenaagapova$ ls -a
.					Alena Borodina - QA Engineer.pages
..					Applications
.3T					Book.txt
.CFUserTextEncoding			Desktop
.DS_Store				Documents
.Trash					Downloads
.Xauthority				Dropbox
.android				IdeaProjects
.bash_history				Library
.bash_profile				Movie.txt
.bash_sessions				Movies
.cache					Music
.config					Pictures
.docker					Public
.dropbox				PycharmProjects

cd

Use the "cd" command to go to a directory. For example, if you are in the home folder, and you want to go to the downloads folder, then you can type in cd Downloads. Remember, this command is case sensitive, and you have to type in the name of the folder exactly as it is.

If you have spaces in the name of the Dirctory use backslash cd Raspberry\ Pi.

If you just type cd and press enter, it takes you to the home directory. To go back from a folder to the folder before that, you can type cd .. . The two dots represent back.

Air-Alena:~ alenaagapova$ cd Music
Air-Alena:Music alenaagapova$ 

Air-Alena:Music alenaagapova$ cd ..
Air-Alena:~ alenaagapova$ 

mkdir & rmdir

Use the mkdir command when you need to create a folder or a directory. For example, if you want to make a directory called “DIY”, then you can type mkdir DIY

Use rmdir to delete a directory. But rmdir can only be used to delete an empty directory. To delete a directory containing files, use rm.

Air-Alena:NEW Dir alenaagapova$ mkdir LOL
Air-Alena:NEW Dir alenaagapova$ ls
LOL

Air-Alena:NEW Dir alenaagapova$ rmdir LOL
Air-Alena:NEW Dir alenaagapova$ ls
Air-Alena:NEW Dir alenaagapova$ 

touch

The touch command is used to create a file. It can be anything, from an empty txt file to an empty zip file. For example, “touch new.txt”.

Air-Alena:NEW Dir alenaagapova$ touch text.txt
Air-Alena:NEW Dir alenaagapova$ ls
text.txt

cp

Use the cp command to copy files through the command line. It takes two arguments: The first is the location of the file to be copied, the second is where to copy.

/** copy to alenaagapova
Air-Alena:NEW Dir alenaagapova$ cp text.txt /Users/alenaagapova

/** check that file is still in current dir
Air-Alena:NEW Dir alenaagapova$ ls
text.txt

/** go to alenaagapova dir
Air-Alena:NEW Dir alenaagapova$ cd ..

/** check that file is there too
Air-Alena:~ alenaagapova$ ls
Alena Borodina - QA Engineer.pages	Pictures
NEW Dir					text.txt

mv

Use the mv command to move files through the command line. We can also use the mv command to rename a file. For example, if we want to rename the file “text” to “new”, we can use “mv text new”. It takes the two arguments, just like the cp command.

Air-Alena:NEW Dir alenaagapova$ touch yes.txt
Air-Alena:NEW Dir alenaagapova$ mv yes.txt no.txt
Air-Alena:NEW Dir alenaagapova$ ls
no.txt		text.txt

Moving file to another directory:

/** move to alenaagapova dir
Air-Alena:NEW Dir alenaagapova$ mv no.txt /Users/alenaagapova/

/** check that file is not in this dir anymore
Air-Alena:NEW Dir alenaagapova$ ls
text.txt

/** check tha file is in alenaagapova dir now
Air-Alena:NEW Dir alenaagapova$ cd ..
Air-Alena:~ alenaagapova$ ls
Alena Borodina - QA Engineer.pages	Public
Movies					no.txt

locate

The locate command is used to locate a file in a Linux system, just like the search command in Windows.

Using the -i argument with the command helps to ignore the case.

If you remember two words, you can separate them using an asterisk (*). For example, to locate a file containing the words "hello" and "this", you can use the command locate -i *hello*this.

/** locate considerinf case:
Air-Alena:~ alenaagapova$ locate no.txt
/Users/alenaagapova/no.txt
/** nothing is found because of uppercase:
Air-Alena:~ alenaagapova$ locate NO.txt

/** locate ignoring case:
Air-Alena:~ alenaagapova$ locate -i NO.txt
/Users/alenaagapova/no.txt

/** locate a file ending with 'ext.txt':
Air-Alena:~ alenaagapova$ locate -i *ext.txt
/Users/alenaagapova/NEW Dir/text.txt
/Users/alenaagapova/text.txt

cat

Use the cat command to display the contents of a file. It is usually used to easily view programs.

Air-Alena:~ alenaagapova$ cat text.txt
hello. This is my text file.


I want to tell you that you are my best friend.


Ciao!

nano, vi

nano and vi are already installed text editors in the Linux command line. vi is simpler than nano.
You can create a new file or modify a file using this editor. For example, if you need to make a new file named "check.txt", you can create it by using the command “nano check.txt”.
You can save your files after editing by using the sequence Ctrl+X, then Y (or N for no).

Air-Alena:~ alenaagapova$ nano text.txt

sudo

A widely used command in the Linux command line, sudo stands for "SuperUser Do". So, if you want any command to be done with administrative or root privileges, you can use the sudo command.

chmod

Use chmod to make a file executable and to change the permissions granted to it in Linux.

Imagine you have a python code named numbers.py in your computer. You'll need to run “python numbers.py” every time you need to run it. Instead of that, when you make it executable, you'll just need to run “numbers.py” in the terminal to run the file.

To make a file executable, you can use the command “chmod +x numbers.py” in this case.

You can use “chmod 755 numbers.py” to give it root permissions or “sudo chmod +x numbers.py” for root executable.

hostname

Use hostname to know your name in your host or network. Basically, it displays your hostname and IP address. Just typing “hostname” gives the output.

Air-Alena:~ alenaagapova$ hostname
Air-Alena.fritz.box

ping

Use ping to check your connection to a server.

Simply, when you type in, for example, ping google.com, it checks if it can connect to the server and come back. It measures this round-trip time and gives you the details about it.

Air-Alena:~ alenaagapova$ ping google.com
PING google.com (172.217.23.78): 56 data bytes
64 bytes from 172.217.23.78: icmp_seq=0 ttl=54 time=106.487 ms
64 bytes from 172.217.23.78: icmp_seq=1 ttl=54 time=98.749 ms

Tips and Tricks for Using Linux Command Line

• You can use the clear command to clear the terminal if it gets filled up with too many commands.
• TAB can be used to fill up in terminal. For example, You just need to type cd Doc and then TAB and the terminal fills the rest up and makes it cd Documents.
• Ctrl+C can be used to stop any command in terminal safely. If it doesn't stop with that, then Ctrl+Z can be used to force stop it.
• You can exit from the terminal by using the exit command.
• You can power off or reboot the computer by using the command sudo halt and sudo reboot.