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Using Unix Goals • Understand the roles of an operating system. • Understand the difference between command-line and GUI. • Understand some basic Unix commands. What is an Operating System? • It is software. • Controls the relationship between all applications and hardware. • Controls the relationship among applications. Command Line Operating Systems • Use letters with symbols, such as C:\>. • Instructions must be typed. • High rate of error – typos! • Some examples of command line operating systems include DOS and Unix. GUI Operating Systems • GUI - Graphic User Interface • Include pictures with descriptive words (icons) • Much easier to move the pointer with the mouse and click on a picture, than to remember commands. • Examples of GUI operating systems include Windows and MAC OS. So, What Does an OS Do? • Controls the INPUT, OUTPUT, and PROCESSING activities for the computer • High-quality O/S can make your computer more effective and efficient • A good OS makes the computer easier to use. The Roles of an OS •A •A •A •A Traffic Cop Communication System Box of Tools Self-Starter A Traffic Cop • Controls the resources of the computer, including memory, file storage, and CPU. • Multitasking (the ability for more than one application to “run” at once) is possible on new computers. A Communications System • Helps all of the hardware components communicate with each other. • Helps applications communicate with the hardware. • Helps applications communicate with one another. A Toolbox • Several utility programs are included with an O/S including File Management, Memory Management, and Networking Tools. A Self-Starter • The OS takes over just after booting. • Checks to see all hardware is present. • “Hard Boot” – turning off the computer and then back on • “Soft Boot” – restarting the computer without turning it off first. Unix • Developed by Bell Labs in 1969 • Command-Line OS • Offered File Sharing • Offered Process-Sharing Introducing Unix Commands • Issue commands from a command prompt: /: • Unix is case sensitive! • Commands are typed in lowercase: cp (copy) is NOT the same as Cp or CP Unix Shells • Unix has a number of shells which help the user interact with the Operating System Kernel (the main program that stays resident in memory and executes OS commands). • Some shells include the Bourne shell, Korn, Bash, TCSH and Csh. Command Syntax • Case sensitive! All commands are lowercase • General Format: command [switches] arg1 arg2 Command Switch Arguments Command Example • Example: ls –l *.html Switch Command Argument Correcting Typographical Errors • DEL key removes the character to the left (in some Telnet clients, BACKSPACE will also do this) • To erase: – C-w – Erases previous word – C-u – Erases an entire line Directory Structures • Unix paths begin with a forward slash • The initial forward slash (/) represents the root directory • Typically, only the system administer has full privileges to the root directory Directory Paths • An absolute path begins at the root: /home/bhecker/public_html/ • A relative path indicates location relative to your present working directory: ../images/ More on Directories • The command pwd will return the directory name in which you are currently working • The directory that represents your personal section of the server is called your home directory Directory Notation • / - represents a directory • /. – represents the current directory • /.. – represents the parent directory • /~ - represents a user’s home directory Creating Directories • Don’t use spaces in directory names. • Use _ (underscore character) or camelCasing to name directories. • Directory names are case sensitive (usually in lowercase, with camel casing). Creating a Directory • Use the mkdir command: mkdir campingImages Name of the directory Command File & Directory Permissions • ls –l command will show full details, including file name, owner name, modification date, size and permission sequence. Unix Permissions • Permission sequence found at the beginning of a directory listing (first 10 characters): World’s Permissions Group’s Permissions Owner’s Permissions Directory d rwx r-x r-x Unix Permissions • The first character represents whether the listing is a directory. If it is a directory, a “d” will appear in the first character; otherwise, you should normally see a dash (-). d rwx r-x r-x Unix Permissions • The remaining nine characters are divided into three triplets. • The first triplet represents the owner’s permissions. • The second is the group’s permissions. • The third triplet represents the World’s permissions. Read Permission • 1st position in a triplet: r stands for Read; grants permission to view the contents of a file or directory (Value is ‘r’ or ‘-’). Write Permission • 2nd position in a triplet: w stands for Write; grants permission to modify a file or the contents of a directory (Value is ‘w’ or ‘-’). Execute Permission • 3rd position in a triplet: x stands for eXecute; grants permission to run an application or open a directory (Value is ‘x’ or ‘-’). Unix Permissions • When changing permissions, we must first decide what number will represent the permissions for a triplet. • We can do this by determining whether or not a permission is turned on or off. • If turned on, a permission gets a value of 1; if turned off, it gets a value of 0. Unix Permissions • After deciding whether the three permissions in a triplet are on or off, we will have a binary number • We can convert the binary number to its octal equivalent Unix Permissions Permissions - - - - x - w - w x Binary 0 0 0 0 0 1 0 1 0 0 1 1 Octal 0 1 2 3 Unix Permissions Permissions r - r – x r w r w x Binary 1 0 0 1 0 1 1 1 0 1 1 1 Octal 4 5 6 7 The chmod Command • Once you’ve established the octal number representing the permission for each triplet, you can then use the change mode (chmod) command to give a directory or file proper permissions chmod Syntax & Example • Syntax: chmod permissionMask file/dir • Example: chmod 755 public_html • Typically, directories and executable files are given “755” permissions, while other files are given “644” permissions Navigating Unix • To move from directory to directory, we use the cd command • Syntax: cd path/ Navigating Unix • To move from a child to a parent directory: cd .. PARENT CHILD Navigating Unix • To move from a grandchild to a parent directory: cd ../.. PARENT CHILD GRANDCHILD Navigating Unix • To move from one child to a sibling directory: cd ../child2 PARENT CHILD1 CHILD2 The List Command • The list command (ls) shows the contents of a directory • We can add switches to the list command to modify what the command can do • To use more than one switch, concatenate them: ls -lt List Command Switches • ls –l shows files in long format, including permissions • ls –a shows hidden files • ls –c shows file listings in a column format • ls –t sorts file listings by last modified date Using Wildcards with ls • ls a* Wildcard, All files starting with 'a' • ls *a* All filenames with 'a' in them • ls *a*html All filenames with 'a' in them and ending with html • ls ????? - All 5 character filenames Using Wildcards with ls • ls [abc]* - All filenames starting with a, b, or c • ls [a-c]* - Same as above but done as a range • ls [^a-c]* - All filenames not starting with a, b, or c The Unix Copy Command • cp can be used to make a copy of a file, leaving the original file untouched • Syntax: cp oldfile [path/]newfile The Unix Copy Command • To make a copy of a file while both the original and copy are in the same directory: cp index.html home.html The Unix Copy Command • To make a copy of a file that results in the copy retaining the original’s name, but is housed in a different directory: cp index.html ../academic/ The Unix Copy Command • To make a copy of a file that results in the copy having a new name and is housed in a different directory: cp index.html ../academic/home.html The Unix Move Command • The mv command has two purposes: – To move files from one directory to another – To rename files • Syntax: mv oldfile newpath/[newfilename] The Unix Move Command • To move a file from one directory to another: mv index.html ../friends/ The Unix Move Command • To rename a file (stays in the same directory): mv index.html home.html The Unix Move Command • To move a file and rename it at the same time: mv index.html ../friends/home.html Deleting Files • Use rm to delete files • Syntax: rm filename Deleting Files • To delete a single file: rm index.html (answer Y to confirm delete) • To delete multiple files using a wildcard: rm *.html (answer Y to confirm delete for each file) Deleting Directories • Use rmdir to delete directories • DIRECTORY MUST BE EMPTY!!!! • Syntax: rmdir directoryname • To delete a directory: rmdir images/ (answer Y to confirm delete) Other Useful Commands • passwd – Password utility that allows users to update their passwords • exit – End your Unix session (you can also use bye) Other Useful Commands • clear – Gives you a blank screen (you can also use cls) • who – Lists users currently logged in to the server Other Useful Commands • finger username – Retrieves information about a user • cal – Displays a calendar of the current month • date – Displays the current system date Other Useful Commands • !! – (pronounced “bang bang”) repeats the last command • ![a..z] – Repeats the last command beginning with selected letter (a-z) Other Useful Commands • |more – Added to commands which display lists to force page stops (Ex: ls –lt |more) • C-z – Temporarily stop a process Other Useful Commands • fg – Bring a process to the foreground after it has been stopped • vacation – Turn on the auto-reply for e-mail • pine – Launch the Pine E-mail client • emacs – Start the Emacs editor Online Manual • Eight Sections – Commands – System calls – Library functions – Devices and device drivers – File formats – Games – Miscellaneous – System maintenance Using man • man command • To lookup help on the cp command: man cp • To lookup help on the ls command: man ls • C-c exits the manual. 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