But whilst man pages are invaluable, they can also be inpenetrable. If it couldn’t find a tmp directory the command would fail. The easiest command to start with, is the directory listing command which is used to list the directory contents. An asterisk ("*") can be used to indicate “zero or more characters”. They’re all just different ways of asking you to open a terminal to get to a shell. The annals of computing history are filled with tales of a mistyped command deleting the entire file system or killing a vital server. Because of this, you should be extra careful when using redirection to make sure that you don’t accidentally overwrite a file you need. Give them a try to see the difference between them. You should take particular care when using wildcards, as it’s easy to accidentally delete more files than you intended. By encouraging use of su the aim was to persuade administrators to spend most of their time using a normal account, only switch to the superuser account when they needed to, and then use the logout command (or Ctrl-D shortcut) as soon as possible to return to their user-level account. But it won’t let you delete a directory. In this example, we will issue the following command. In case you hadn’t guessed, mkdir is short for ‘make directory’. This is variously described as being short for ‘superuser’ or ‘switch user’, and allows you to change to another user on the machine without having to log out and in again. This command line guide is intended for the absolute beginner users wishing to learn the basics of GNU/Linux command line. It’s perfect for file management, development, remote administration and a thousand other tasks. If you do want to append to, rather than replace, the content of the files, double up on the greater-than character: Repeat the first cat a few more times, using the Up Arrow for convenience, and perhaps add a few more arbitrary echo commands, until your text document is so large that it won’t all fit in the terminal at once when you use cat to display it. What’s more important is that you’ve learnt the key aspects of working with the shell. Table 6. Ubuntu - Scripting - Since we have the ability to work with the command line which we covered in the previous chapter, it is common to create scripts which can perform simple jobs. Don’t be alarmed if you run a command and another prompt immediately appears, as that usually means the command succeeded. Most Linux command line tools include a man page. At least now you’ll understand what’s happening, even when you can’t easily see the file in your graphical tools. To open a terminal emulator window, click the Gnome Applications menu and select Accessories → Terminal, then, use these commands: clear Clears the current screen of all text. # Zip all pdf files in the ~/tmp/pdf/ diretory zip ~/targetdir/myzip.zip ~/tmp/pdf/*.pdf # Unzip the zip file unzip ~/targetdir ... On the command line Ubuntu allows to install / remove and search for packages via the following commands. This is its working directory. Later we’ll install a useful tool to visualise the structure, but you’ve already got enough knowledge to confirm it: The “-p” that we used is called an option or a switch (in this case it means “create the parent directories, too”). It is easy to use and equally easy to install. If you follow any instructions that tell you to run sudo su, be aware that every command after that will be running as the root user. Worse still, if you lose track of which user you’re currently operating as, you might issue a command that is fairly benign when run as a user, but which could destroy the entire system if run as root. Be extra careful with case when typing in the command line. This list provides some simple command line examples. But this time we’ve added three things after the mkdir command. That is, the place you end up at depends on your current working directory. ls Lists the current directory. If you’re coming from a Windows background you’re probably used to each drive having its own letter, with your main hard drive typically being “C:”. We could cd into dir1 then use mv combined.txt .. to say “move combined.txt into the parent directory”. To avoid re-typing each command after the first, use the Up Arrow to pull up the previous command in the history. pwd is an abbreviation of ‘print working directory’. These files typically store your personal configuration, and is how Unix systems have always offered the capability to have system-level settings (usually in /etc) that can be overridden by individual users (courtesy of hidden files in their home directory). sudo's switches all start with one or two hyphens and must immediately follow the sudo command, so there can be no confusion about whether the second parameter on the line is a command or an option. If you can’t find a launcher, or if you just want a faster way to bring up the terminal, most Linux systems use the same default keyboard shortcut to start it: Ctrl-Alt-T. Unless you know exactly what the file is doing, you’re opening up a hole through which malware could potentially be installed onto your system. We’ll look at case a little more on the next page but, for now, just make sure to type all the following lines in exactly the case that’s shown. The command line is a quick, powerful, text-based interface developers use to more effectively and efficiently communicate with computers to accomplish a wider set of tasks. In an effort to reduce these problems many Linux distributions started to encourage the use of the su command. Instead of dir2 it should have been put in dir6, which is the one that’s inside dir5, which is in dir4. Linux provides a CLI (Command Line Interface) to communicate with the OS. If the instructions require you to first add a new software repository to your system, using the apt-add-repository command, by editing files in /etc/apt, or by using a “PPA” (Personal Package Archive), you should be careful as these sources are not curated by Canonical. In practice you’ll still most likely use a graphical program when you want to move, rename or delete one or two files, but knowing how to do this using the command line can be useful for bulk changes, or when the files are spread amongst different folders. The second is when you used cd / to switch to the root directory. You can often tell a person who uses the command line a lot just from their file names: they’ll tend to stick to letters and numbers, and use underscores ("_") or hyphens ("-") instead of spaces. See what happens when you try to pass the wrong number of parameters to a command: Back to our new directories. Even system configuration files can often be viewed (with cat or less) as a normal user, and only require root privileges if you need to edit them. There are a couple of basics to understand here, before we get into the detail of what the command actually did. Most seasoned command line users tend to stick primarily to lower case names for their files and directories so that they rarely have to worry about file name clashes, or which case to use for each letter in the name. Package management; Everything was sent as text, and received as text. The default terminal shell for Ubuntu is called Bash , an acronym for “Bourne-Again SHell”. Step 2 − The search result of Terminal appears. Pipe the output through wc -l to give you a clearer idea of how many hidden files and folders have been right under your nose all this time. Installing directly from your distro’s official software repositories is the safest option, but sometimes the application or version you want simply isn’t available that way. ls (list) command lists all files and folders in your current working directory. This command is used to display who is the current logged on user. When installing via any other mechanism, make sure you’re getting the files from an official source for the project in question. The traditional Unix command line handles a rename as though you’re moving the file from one name to another, so our old friend mv is the command to use. The key to this approach is a command called sudo (as in “switch user and do this command”). During the formative years of the computer industry, one of the early operating systems was called Unix. Surely that can’t be right? ls (List) ls command stands for list. Be careful with sudo Linux is a sort-of-descendent of Unix. Again, it’s a small safety net to prevent you from accidentally deleting a folder full of files when you didn’t mean to. Nearly every command and application in Linux will have a man (manual) file, so finding them is as simple as typing "man "command"" to bring up a longer manual entry for the specified command. The shell is an application whose main purpose is to run other applications by entering commands, and is often called a command-line shell because you execute commands line-by-line by pressing Enter. The mkdir command expects at least one argument, whereas the cd command can work with zero or one, but no more. As for our recently installed tree command, that works in a similar way (except without an appearance by . The Linux Command Line Second Internet Edition William E. Shotts, Jr. A LinuxCommand.org Book Good naming practice We’ll assume no prior knowledge, but by the end we hope you’ll feel a bit more comfortable the next time you’re faced with some instructions that begin “Open a terminal”. If your file is very long, you might want to pipe it through less to make it easier to inspect: It appears that very few, if any, of our duplicate lines are being removed. Again, if you see mention of “command line”, including in the title of this very tutorial, it’s just another way of talking about a shell running in a terminal. root is also the name that has been used for the superuser since the early days of Unix. Ubuntu is a Linux based operating system and most Linux users are more familiar with the command line interface. If you just run ls on its own you should see that the output.txt file has been created. The first is when you run cd on its own to go straight to your home directory. All we need to do is to add the greater-than character (">") to the end of our command line, followed by the name of the file to write to: This time there’s nothing printed to the screen, because the output is being redirected to our file instead. Or you could save a lot of typing by passing a path directly to the ls command to get straight to the confirmation you’re looking for: Now suppose it turns out that file shouldn’t be in dir1 after all. If we were to sort the contents of the file alphabetically, that would do the trick. By minimising the amount of time spent logged in as root, the use of su reduces the window of opportunity in which to make a catastrophic mistake. When logged into a Unix mainframe via a terminal users still had to manage the sort of file management tasks that you might now perform with a mouse and a couple of windows. if you are at your home directory then it will print something like /home/ ls list directory: This command will list the items of a directory. ls. registered trademarks of Canonical Ltd. How to access the command line from your own computer, How to perform some basic file manipulation, How to chain commands together to make more powerful tools, A computer running Ubuntu or some other version of Linux. You can still work with the hidden file by making sure you include the dot when you specify its file name: If you run ls you’ll see that the .hidden directory is, as you might expect, hidden. You can also specify … In the case of rmdir we can add a -p switch to tell it to also remove the parent directories. Now let’s create another copy of the file, in our working directory but with a different name. Try taking a brief look at the pages for some of the commands you’ve already encountered: man ls, man cp, man rmdir and so on. This command will display the current working directory. If anyone asks you to enable the root account, or log in as root, be very suspicious of their intentions. The Linux command line is a text interface to your computer. Learning how to use it will allow you to discover all that your computer is capable of! Plus, you’ll learn a few more things about the command line along the way. In this section you’ve learnt about the dangers of the root account, and how modern Linux systems like Ubuntu try to reduce the risk of danger by using sudo. The output will be the listing of the directory contents. Whether it’s the file name itself, GPS coordintates embedded in photos you take on your phone, or the metadata stored in an audio file, text still plays a vital role in every aspect of computing. The core part of Linux is designed to behave similarly to a Unix system, such that most of the old shells and other text-based programs run on it quite happily. With what we now know about paths, that’s no problem either: Notice how our mv command let us move the file from one directory into another, even though our working directory is something completely different. There’s little we’ve covered here that is likely to make you abandon your graphical file manager in favour of a prompt, but file manipulation wasn’t really the main goal. Click the mouse into the window to make sure that’s where your keystrokes will go, then type the following command, all in lower case, before pressing the Enter or Return key to run it. In this chapter, we will go through some of the popular command line’s used in Ubuntu. There’s even a man page for the man program itself, which is accessed using man man, of course. Tutorials. This is a powerful property of the command line: no matter where in the file system you are, it’s still possible to operate on files and folders in totally different locations. If you plan to use the terminal a lot, memorising Ctrl-Alt-T to launch the terminal and Ctrl-D to close it will soon make it feel like a handy assistant that you can call on instantly, and dismiss just as easily. can be used to represent the current working directory. For instructions targeting Ubuntu, a common appearance of sudo is to install new software onto your system using the apt or apt-get commands. Instead it deletes them totally, utterly and irrevocably. Our command to move the file back into the working directory therefore becomes this (note the space before the dot, there are two parameters being passed to mv): The mv command also lets us move more than one file at a time. However you launch your terminal, you should end up with a rather dull looking window with an odd bit of text at the top, much like the image below. The format of man pages is often terse, think of them more as a quick overview of a command than a full tutorial. man command, info command and command --help are the most important tools at the command line. Difficulty: 1 out of 5. containers The Ubuntu desktop includes everything you need to run your organization, enterprise, school or home. But we can use another path shortcut to avoid changing directory at all. Will it append the text to the file, so it contains two copies? It can be useful when you need to run a series of commands as the superuser, to avoid having to prefix them all with sudo, but it opens you up to exactly the same kind of problems that were described for su above. The information on the command will be displayed. Difficulty: 1 out of 5. desktop Install Ubuntu desktop. If you run ls you’ll see that most of the folders have gone, but folder_6 is still hanging around. To understand why, we need to look at the documentation for the uniq command. Important Warning If you try to create new files or directories, view existing files, or even delete them, the shell will assume you’re looking for them in the current working directory unless you take steps to specify otherwise. The tree program is only small, so it shouldn’t take more than a minute or two to download and install for most users. pwd print work directory: e.g. Make sure you change both appearances of the number in each of these lines. Let’s wander around the file system a little, and keep an eye on the prompt as you do so: You must be bored with just moving around the file system by now, but a good understanding of absolute and relative paths will be invaluable as we move on to create some new folders and files! From the root directory, the following command will move you into the “home” directory (which is an immediate subdirectory of “/”): To go up to the parent directory, in this case back to “/”, use the special syntax of two dots (..) when changing directory (note the space between cd and .., unlike in DOS you can’t just type cd.. as one command): Typing cd on its own is a quick shortcut to get back to your home directory: You can also use .. more than once if you have to move up through multiple levels of parent directories: Notice that in the previous example we described a route to take through the directories. First is that when you type a command it appears on the same line as the odd text. ScriptingHowto. The output is automatically piped through your pager, which will typically be less, so you can move back and forth through the output, then press q when you’re finished: Because this type of documentation is accessed via the man command, you’ll hear it referred to as a “man page”, as in “check the man page for more details”. Let’s give it a go: You probably didn’t even need to type that one in to guess what would happen: two new folders, one called another and the other called folder. Don’t use the root account Today’s computers and phones have the sort of graphical and audio capabilities that our 70s terminal users couldn’t even begin to imagine. Where those instructions require changes to your machine that go beyond modifying a few files in your home directory, you’ll inevitably be faced with commands that need to be run as the machine’s administrator (or superuser in Unix parlance). If you are asked to use su with a username then (if you have the password) you will have access to all the files of that user, and could accidentally delete or modify them. We’ve reached the end of this tutorial, and you should be back in your home directory now (use pwd to check, and cd to go there if you’re not). This assumes that you are running any version of Ubuntu Linux and have a desire to learn its inner workings. This speed and efficiency is one reason why this text interface is still widely used today. The original Unix shell program was just called sh, but it has been extended and superceded over the years, so on a modern Linux system you’re most likely to be using a shell called bash. You can change the working directory using the cd command, an abbreviation for ‘change directory’. But any use of superuser powers should be considered carefully. Other versions of Linux, or other flavours of Ubuntu, will usually have a terminal launcher located in the same place as your other application launchers. Now that we’re safely inside our test area (double check with pwd if you’re not certain), let’s create a few subdirectories: There’s something a little different about that command. The output will contain information on the ls command. Any other parameters will be passed directly to the new command. These days there’s a far better pager that you should use instead: because it replaces more, the programmers decided to call it less. Directoryname − This is the optional directory name that can be specified along with the ls command. But often the instructions just require you to install software from the standard repositories, which should be safe. Step 1 − Go to the search option and type the command keyword. For example, a software publisher’s site might ask you to download a file and change its permissions, then use sudo to run it. In this next section we’re going to start deleting files and folders. My drive is /dev/sdd. We will proceed by briefly describing the command line interface and giving some history. But we have seen two commands that are absolute. Windows, for example, is case-insensitive, so it would treat all three of the file names above as being a single file, potentially causing data loss or other problems. sudo apt-get install gnome-system-tools The apt-get command line is used to install additional packages from the Internet for the Ubuntu system. A developer’s productivity can be improved greatly by utilizing the command line interface effectively. If, however, you’re intrigued by the ability to affect files in disparate parts of your hard drive with just a few keypresses, there’s still a lot more for you to learn. Don’t worry too much about which shell you have, all the content in this tutorial will work on just about all of them. Unlike graphical interfaces, rm doesn’t move files to a folder called “trash” or similar. No matter what your current working directory is, they’ll have the same effect. Fortunately the Unix command line provides a shortcut that avoids you having to create a temporary file, by taking the output from one command (referred to as standard output or STDOUT) and feeding it directly in as the input to another command (standard input or STDIN). Before we conclude this tutorial it’s worth mentioning hidden files (and folders). Or will it replace it entirely? In older systems it was a real user, with a real username (almost always “root”) that you could log in as if you had the password. Don’t use su Then mount the ubuntu.iso file with the below commands in terminal: sudo mkdir /media/iso/ sudo mount -o loop /path/to/ubuntu.iso /media/iso Insert your USB flash drive. The directory listing of the current directory will be shown as the output. On the subject of synonyms, another way of looking at the prompt is to say that there’s a line in the terminal into which you type commands. It’s like the MS-DOS dir command. So if we wanted to go straight from our home directory to the “etc” directory (which is directly inside the root of the file system), we could use this approach: Most of the examples we’ve looked at so far use relative paths. The uniq man page is a typical example in that it starts with a brief one-line description of the command, moves on to a synopsis of how to use it, then has a detailed description of each option or parameter. Let’s take a look at them with the ls (list) command: If you’ve followed the last few commands, your terminal should be looking something like this: Notice that mkdir created all the folders in one directory. In this tutorial, you will learn how to flash Ubuntu Server on a microSD card for Raspberry pi 2, 3 and 4. Well, it turns out that rm does have one little safety net. As you’ve seen, using “/” at the start of your path means “starting from the root directory”. The command in this case is apt. Commands to Shutdown Ubuntu Linux via Terminal Open command terminal or if you are using a server with CLI interface then you are already there. We’ll assume no prior knowledge, but by the end we hope you’ll feel a bit more comfortable the next time you’re faced with some instructions that begin “Open a terminal”. Warning These are commonly used on Linux systems to store settings and configuration data, and are typically hidden simply so that they don’t clutter the view of your own files. Compared with graphics, text is very light on resources. Etcher is a strong OS image burner tool for Windows, Mac, and Linux. Because we know there’s only one file in dir1 we can also just use “*” to match any filename in that directory, saving ourselves a few more keystrokes. The question, then, is how to rearrange the lines in our file so that duplicate entries are on adjacent lines. When following instructions you find online you should now be in a better position to spot those commands that might require greater scrutiny. Difficulty: 2 … But suppose we want to create a directory with a space in the name? Now your working directory is “/”. Users could even write simple code (called “shell scripts”) which could be used to automate long series of shell commands in order to make complex tasks easier. Without the forward slash at the start the mkdir command would try to find a tmp directory inside the current working directory, then try to create a tutorial directory inside that. Typing PWD instead of pwd will produce an error, but sometimes the wrong case can result in a command appearing to run, but not doing what you expected. That text is there to tell you the computer is ready to accept a command, it’s the computer’s way of prompting you. Login to your terminal and execute the following systemctl command to start GUI: $ sudo systemctl isolate graphical ls dir Lists the specified directory. In this tutorial, we will be learning how to install Etcher on Ubuntu. In short, root can do just about anything, skipping easily round the safeguards that are usually put in place to stop users from overstepping their bounds. Lop off the last pipe to see the output of the command for a better idea of what’s happening. You can then edit the command before you run it by moving the cursor left and right with the arrow keys, and removing the character to the left with Backspace or the one the cursor is on with Delete. One important concept to understand is that the shell has a notion of a default location in which any file operations will take place. Commands that don’t need root access, something as mundane as pwd or ls, would be run under the auspices of the superuser, increasing the risk of a bug in the program causing major problems. In this screenshot of Ubuntu 18.04 you can see the option at the top of the dialog: Assuming you’re on a Linux system that uses sudo, and your account is configured as an administrator, try the following to see what happens when you try to access a file that is considered sensitive (it contains encrypted passwords): If you enter your password when prompted you should see the contents of the /etc/shadow file. Changing directory by specifying the directory name, or using .. will have different effects depending on where you start from. and .., also appear as though they’re real directories. Instead they have a single unified file system, and individual drives can be attached (“mounted”) to whatever location in the file system makes most sense. On a Ubuntu system the first user created when the system is installed is considered to be the superuser. sudo is used to prefix a command that has to be run with superuser privileges. Many manuals If you’re using Ubuntu the root account is disabled by default, so su with no parameters won’t work. The addition of options to our rm or rmdir commands will let us perform dangerous actions without the aid of a safety net! In practice it works like this: The sudo command, when used without any options, will assume that the first parameter is a command for it to run with superuser privileges. Too many roots Unix has a command, uniq, that will only output unique lines in the file. But sometimes it’s handy to be able to do exactly that, and mkdir does have a way: This time you’ll see that only dir4 has been added to the list, because dir5 is inside it, and dir6 is inside that. 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