Tutorial 1: Unix Basics

Transcription

1 Tutorial 1: Unix Basics To log in to your ece account, enter your ece username and password in the space provided in the login screen. Note that when you type your password, nothing will show up in the password field; don t worry this is normal. Also, text in UNIX is case-sensitive. Therefore if your password is Qrtw4A and you type qrtw4a, it will be considered an incorrect password. Be careful NOT to use the tab key to move between fields as this does not work in UNIX. Instead of moving the cursor to the next field, hitting the tab key will add a tab character to the current field and thereby prevent you from logging on. If this is the first time you login today, you will next see the Message of the day. Read this announcement. Note: Before clicking OK notice some of the things you can do with your mouse in the UNIX environment. 1. Place your cursor on a word in the text of the Message of the day. 2. Double-click with the left button of your mouse to select a word. 3. Select a line by triple clicking with the left button of your mouse. 4. Select the paragraph by clicking four times with the left button of your mouse. 5. Select the entire text (can you guess?) by clicking five times with the left mouse button. UNIX also offers some interesting scroll functionality. You can grab the scroll bar by clicking and holding down with the middle mouse button on the scroll bar. For as long as you hold down the middle mouse button you can control scrolling by clicking on the scroll bar with the left button to scroll down, and with the right button to scroll up. What s more, the increment of the scroll varies depending on where you click on the scroll bar. For example, if you click at the top of the scroll bar with the left mouse button, the text will scroll up only a little. However, if you click the left mouse button in the middle of the scroll bar, the text will scroll down significantly. When you are comfortable with this, click OK at the bottom of the Message of the Day. Click I Accept on the following window. WELCOME TO YOUR UNIX WORKING ENVIRONMENT! The little black window that says xterm at the top is the window from which you will later compile your programs. It is also the window that will require your familiarity with some UNIX terminology and syntax. But let s not worry about that for now and take a quick look around.

2 Notice on the bottom right hand side of your screen that there is a little square divided into four smaller squares. Each one of those smaller squares represents a screen available to you. The default screen you are presently using is represented by the small square in the top left hand corner. As you can see, there is an xterm window open on this screen. To view other available screens, click on the other small squares. These screens are presently blank. Now, come back to the original screen with the xterm window already open. 1. Click on the desktop with the left mouse button. 2. Consider the menu that appears before you. 3. Select Utilities. 4. Select Nedit. This is the text editor with which you will be writing your C++ code. 5. Type the following: Hello, I am creating a file. Blah. 6. Okay, now we want this file to be a little bit longer so we can play with it, but we don t want to retype blah a million times, so let s just copy and paste it. 7. Select the word Blah as we did before by double-clicking with the left button of your mouse (or holding the left mouse button, dragging to select your text, then releasing the button). 8. Now you can paste that selection, as many times as you please, by clicking with the middle mouse button where you would like it to be pasted. There are a few things to note here. First, you cannot select a paragraph by clicking four times with the left mouse button (as before), doing so will select the entire text. Second, you can only past text so long as it is still selected, much as with Microsoft Excel in Windows. That means that if you copy a word and then click away, you will not be able to paste. The pasted text will be placed at the current cursor position. 9. When you have approx. twenty lines of blah blah it is time to save the file. 10. Click on File at the top of the Nedit window, Select Save As. The directory in which your file should be saved, your home directory, appears by default (i.e. the directory that is the same as your username). In the space provided under Save File As:, name your file First.cpp The extension cpp is generally reserved for C++ programs, but we want to start a good habit here, so let s just go with that. All right, that having been said, let s get our hands dirty with so UNIX commands! In UNIX, your location in the file system hierarchy is known as your current working directory. When you log in, you are automatically placed in your home directory. (i.e. directory with the same name as your username)

3 1. Go back to your xterm window and type pwd and press enter. This command, print working directory, will always show you where you are if you get lost. It so happens that your account is setup such that your current working directory is displayed as part of your command prompt (i.e. where you type your commands in the xterm window). 2. To change directories we use the cd (change directory) command. Let s do an example together. Type the following and press enter. cd.. This command moves you up one level in the directory tree because.. is UNIX shorthand for the parent directory (Note: a space is required between cd and.. ). 3. Now type pwd again to see where you are. 4. Compare this result with the previous one, and notice how you have moved up one level. 5. To get back to your home directory, simply type cd without an argument and press enter. This will always bring you home no matter how lost you are. 6. Type pwd and press enter one last time to assure yourself that you are in fact home. If you want to move forward in the file system hierarchy, you can still use the cd command. Consider your current working directory (the last part of your last output). Move up one level by typing cd.. and now move into your home directory (down one level) by typing: cd your_username Of course don t type your_username, type the name of your home directory, which is your username. Now enter pwd to ensure for yourself that you have returned to your home directory. If for some reason you are now lost, type cd press enter and try the above sequence of commands again. Use the cp command to copy a file: 1. Type cp First.cpp Second.cpp and press enter (make sure you are in your home directory otherwise First.cpp will not be found!). 2. Now type ls and press enter to list the contents of the current directory. Notice that you have a new file in your home directory called Second.cpp. To see what s in this file, type less Second.cpp and press enter. Notice that the content is identical to the content of the original file First.cpp. less is a text file viewer and you can use the arrow keys to go up and down. Press q to quit, or h for help.

4 Moving and renaming files is equally straightforward. The UNIX mv command moves files and directories. You can move a file to a different location in the file system, or change the name by moving the file within the current location. For example, let s rename Second.cpp to Third.cpp. 1. Type mv Second.cpp Third.cpp and press enter. 2. Now type ls and press enter to list the contents of your home directory. Notice that there is no more Second.cpp file, but there is a Third.cpp file. To delete (remove) the file Third.cpp: 1. Type rm Third.cpp and press enter. 2. You will be asked to confirm the deletion. To confirm you wish to delete the file, press y and enter. 3. Now type ls and enter and Third.cpp should be deleted. These are only some of the most basic UNIX commands, but they are the only commands you really need for the time being. Rest assured, however, that the more comfortable you are at manipulating these commands, the less stressful your programming experience will be. To close your xterm window, type exit in the xterm window and press enter. To close Nedit, click on the x in the top right hand corner of that window. Important: Never forget to quit your session before leaving the computer labs. You wouldn t want anyone using your account without your consent. Exiting the ECE system To quit your session, click on the desktop with the left mouse button as before and select Quit from the drop down menu. See you soon!

5 Here are some bonus commands and exercises for those of you who breezed through the first lab. Creating a directory Create a directory called test within your home directory mkdir test You can now move your file First.cpp into this directory by typing mv First.cpp test/first.cpp Note that this will not change the name of the file, it will only move it to the new test directory. Removing a directory To remove the directory you just created, first move that file back so that the directory is empty, then use the rmdir command to remove the test directory. mv test/first.cpp First.cpp rmdir test Time Savers and Help You do not have to re-type commands that you have used before; you can simply use the up arrow key to navigate through previous commands. Try it, press the arrow up key a few times and notice that UNIX is listing the commands you have used in order of most to least recent. Also, if you want to look at something that you displayed earlier in the xterm window, but can no longer see, you can scroll up by pressing shift and page-up at the same time. You can also scroll back down by pressing shift and pagedown at the same time. If you are really brave and want to learn about UNIX using the built in manual, you can type man man and press enter. This will display a huge amount of text, but don t feel overwhelmed, since it is not intended to be read start to finish. Navigate through the text the same way you were scrolling (shift-pageup, shiftpagedown) or press q to quit. To find out about a specific command (say the ls command), simply type man ls.

6 Additional UNIX reference For a more comprehensive Unix reference, obtain the Unix Survival Guide available on the Electrical and Computer Engineering (ECE) website. Go to in Netscape, then click on Documentation (on top of page), then choose Other Tutorials from the menu on the side. You should then see links for the Survival Guide in the main browser screen. It is best to view the pdf version of the survival guide so click on the link PDF, 41 pages. A Save As window will come up requesting you to save the file. Just click OK to save it. Now to view your file (pdf format), open up the Acrobat Reader program: 1. Left-click on the Unix desktop, move to "Utilities" and in the submenu, left-click on Acroread". 2. Now that you've started Acrobat Reader, open up the Unix Tutorial you've saved by going to "File", then "Open". The "Open" menu will be displayed and on the right you should see the file "Unix_Tutorial_v23.pdf". It may have been updated, so the filename may not be exactly as shown. 3. Left-click on this file and then choose "Open". If you were successful, the document should now be displayed in Acrobat Reader.