Basic UNIX

 Nothing seems to stir dread in Windows and DOS users more than being faced with the prospect of having to use UNIX for the first time. Yes its true that UNIX is a very sophisticated operating system with a million commands, but you can most likely do everything you need as a webmaster with just a few of them. Think about what commands you use most of the time with DOS! 

What you need to find out are the locations of home directories and web directories. Your host or service provider can fix you up with this information. 

This page is a quick introduction to the several commands and things you need to know about UNIX. Believe me, you can learn about UNIX on the 'Net- in fact most of the Internet runs on UNIX servers. Print out this page, put it on your lap- and voila you too are a UNIX Guru!

Important Differences Between UNIX and DOS
Despite common belief, switching your mindset from DOS to UNIX is not very hard. There are several things you should be aware of that will instantly make your life easier. 
  • The end of file character is control-D, not control-Z 
  • UNIX ends its lines with only a control-J. Remember to FTP your HTML and text files from DOS to UNIX using ASCII mode. UNIX will ignore the control-m's, but they look ugly. 
  • UNIX is case sensitive. It is important to remember that IMAGE.JPG and image.jpg are not the same. The normal convention in UNIX is to use lower case letters, but this is not law. 
  • In UNIX, you do not use the backslash, but rather the forward slash when referencing directories. The backslash tells UNIX to take the character after it literally. So cd \dir\dir would be cd dirdir. 
  • cd with nothing after it takes you to your home directory, it does not print out your present working directory. That would be the pwd command! 
  • UNIX does not have an unerase command. Once you delete a file, it is gone forever. 
  • Command options in UNIX generally use the hyphen-, not the forward slash. 
Navigation: Same commands, but...
Getting around in UNIX is very similar to getting around in DOS. The only source of confusion is that when Bill Gates decided to have PC-DOS support a tree directory structure, he had his car running in the garage that night. In other words- Whenever you have an urge to hit the backslash, hit the forward slash key instead.
  • pwd tells you what directory you are in. 
  • cd alone returns you to your $HOME directory. 
  • cd .. takes you up one level. 
  • cd dirname moves you to the directory named "dirname". 
File Handling
Unix and DOS have the same utilities for dealing with files and directories- only some of the names have been changed...
  • cp Works just like copy in DOS.

    • Syntax: cp file1 file2
  • rm Replaces the DOS erase command.

    • Syntax: rm file
  • mv Does what rename does in DOS.

    • Syntax: mv file1 file2
  • mkdir is the same as in DOS.

    • Syntax: mkdir dirname
  • rmdir is the same as in DOS.

    • Syntax: rmdir dirname
  • ls is the UNIX version of dir.

    • Syntax: ls -l shows long (detailed) listing.
    Syntax: ls -last shows long listing- newest first.
    Syntax: ls -c is like dir /W
File Permissions
DOS has a limited utility for setting permissions on files: ATTRIB. In UNIX (being that it is a true multi-user, multitasking operating system), has a more sophisticated method of setting permissions: the chmod command. To understand it, let's look at a small directory listing as made with the ls -l command.  
  drwxrwxr-x    1 bnb      xbignose    1018 Apr 30 23:45 mydir
  -rw-rw-r--    1 bnb      xbignose   18755 Apr 30 23:37 mypic.gif
  -rwxrwxr-x    1 bnb      xbignose   18525 May  4 02:48 mycommand
  
The permissions are indicated by a series of rwx's on the left side of the listing. The first position indicates the type of file. For our purposes it is always a "-" for a file, or a "d" for a directory. 

The remaining nine characters indicate the permissions given to the owner, group, and others. Since owner and other both start with the letter "O", think of owner as the user. Here is the nitty gritty... 

  • X means execute permission- except for directories where it means search permission. 
  • The first three permission characters are for the user (owner), the middle three are for the group, and the last three are for all other people on the system. 
  • chmod 775 dirname is the normal permission for a directory. drwxrwxr-x 
  • chmod 664 filename is the normal permission for a non-executable file, i.e., an HTML or image file. 
  • chmod 775 filename is the normal permission for an executable file, i.e., a shell script. Usually these are not in your web directory. 
Many of you without telnet access that use an FTP program such as Cute-FTP or WS-FTP, will have to use the unix command function of your program. Check the help file with your FTP program for the exact instructions. 

Text Editors
The main editors available on most UNIX systems in order of appearance are: 
  • vi. The most popular UNIX editor. Can be found on every system. Takes some getting used to, but is very addictive! recommended.Here is an excellent Quick tutorial. 
  • emacs. Very powerful. Very complicated. 
  • pico. On screen reminders of comand keys. 
For more documentation...
Every UNIX system has on-line documentation. It is identical to the paper manual pages. In order to use this feature, you must be able to access your site and login using a TELNET program. 

Getting help is as simple as entering the command:  

          man command
  
The man command will format and display the manual pages for the command you request. Not all of the instructions you will find will make much sense as ALL options for a command are presented, but most have simple examples. 

Congratulations!
Guess what? You have graduated! This pretty much covers the material of a two day Introduction to UNIX course- retail value is about $595.