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Useful Linux Commands
The following will help you get started with Linux on the SCS Network. It will only describe the very basics. For an in-depth look at Linux, the internal workings, and how the operating system works see the O'Reilly set of books in particular 'Essential System Administration' by Aeleen Frisch.
Opening a Terminal Window
Linux has a window manager, and windows that you can work with. (SCS uses Gnome as the default window manager). Although GUIs are useful, and many tasks can now be done using GUIs, much of the work in Linux is still done on the command line. Essentially all work can be done on the command line, without using the GUI at all. The terminal window is used to type command line arguments. For the Gnome window manager you have to access the menu (top left corner icon) and then select “Accessories – Terminal”.
Basic Linux Commands
When using a Linux command line, the following commands are essential to navigating around the system:
| Linux Command | DOS Command | Description |
|---|---|---|
ls | dir | List the files in a directory. Usage: ‘ ls’ or ‘ls directory’ |
cd | cd | Change to a different directory. Usage: ‘ cd directory’Some special examples are ‘ cd ..’ which moves up one directory, or ‘cd ~’ which switches to your user home directory. |
rm | del, deltree | Delete files or directories. Usage: ‘ rm file’ or ‘rm -r directory’ |
cat | type | Display the contents of a file. Usage: ‘ cat file’ |
clear | cls | Clear the screen. Usage: ‘ clear’ |
mkdir | mkdir | Create a new directory. Usage: ‘ mkdir directory’ |
cp | copy | Copies files or directories. Usage: ‘ cp file destination’ or ‘cp -R directory destination’ |
mv | ren, move | Move or rename files or directories. Usage: ‘ mv file destination’ |
find | Locate files within a directory. Usage: ‘ find directory -name file’Example: ‘ find ~ -name '*.c'’ will find all of the C source code files in your home directory. |
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tail | Display the last few lines of a file. Usage: ‘ tail -n lines file’Example: ‘ tail -n 20 project.c’ will display the last 20 lines of the source code in project.c. |
For more help with Linux commands, you can use the built-in help system. Type ‘man command’ to see the help page for a particular command. In addition, you can read the online unix help.
Linux Command-Line Examples
Here are some examples of more complicated commands which you may find useful.
| Linux Command | Description |
|---|---|
less README.txt | Display the file README.txt on the screen, allowing you to scroll through it with arrow keys. Press ‘Q’ to exit. |
date > date.txt | Get the current system date and time, and save the output to the text file date.txt |
grep keyword README.txt | Search the file README.txt for keyword, and display any matching lines. |
uname -a | Display the version of the operating system which you are using. |
tar -acvf archive.tar.gz project/ | Create a compressed archive of a directory, much like a zip file. |
tar -xvf archive.tar.gz | Extract a compressed archive to the current directory. |
whoami | Display the name of the user that you are currently logged in as. |
ssh lambda02 | Use a secure, encrypted protocol to log into a different computer. You will get a command prompt on the remote computer. You can use exit to return to your original computer. |