UNIX

The most basic commands in Unix are:

• login :log on to the computer
• passwd :change your password
• cd :change directories
• pwd :print working directory
• mkdir :make new directory
• ls :list contents of a directory ls -al gives more
• cp :copy a file or directory
• mv :move or rename a file or directory
• rm :delete (remove) a file. CAREFUL this is permanent!
• man :get the manual page for a given subject
• more :print contents of a file to the screen
• lpr :send contents of a file to the laser printer’
• ps :list processes running (or sleeping) ps -r for active ones ps -el for more
• exit: log off of the computer

There are few important concepts in Unix:

1. The shell:

When you login to the computer does two things: It reads and executes any statements in your .login file and it starts a shell and reads and executes statements in a start-up script. There are several shells. Yours will be bash. The bash start-up is .bash_profile. You have one of these already but you may modify it if you wish. To logout type exit to get out of the shell.

2. File systems:

The directories in Unix are hierarchical. The top of the directory systems is the / or root directory. This directory and all its files belong to the "root" or "super" user. When you login, the machine will place you in your home directory. After logging in, to go to the directory /usr/local/bin you could type:

cd /usr

cd local

cd bin

or you could simply type

cd /usr/local/bin

3. File types and permissions:

There are four basic types of things you can see in a directory. Regular ASCII (human readable) files, executable files, directories and links. ASCII files can only be read/write (either by your or a command or program). Executable files are executed on the command line or by another command or program. Directories are places in the file systems where files and directories are kept. Links are simply pointers in one directory to files or directories in another directory. Hidden files are noted by a . as in . profile. Hidden directories are shown by . / .

4. Processes:

A Unix machine is a multi-tasking computer. Many processes can run simultaneously either silently or to/from STDOUT/STDIN. The ps command tells you what processes you are running. If in the middle of a process you type CTRL-C (control c), the process will interrupt; it can’t be started again. If, on the other hand, you type CTRL-Z (control z), the process is stopped; it can be started again by typing fg (foreground). You can kill a process by getting the PID number of a process (use ps) and typing kill PIDnumber. Typing logout may kill some processes in that shell but it may not get them all. You can run a process in the background (you get your prompt back) by typing commandname &.

5. To edit files:
Textwrangler is nice. Textedit works also but it writes an .rtf file as default NOT an ASCII file.

You should also have web browsers, Excel and other software available in the Application directory.