Basic Unix Commands

UNIX is "Simple"!. If you are familiar with DOS (disk operating system used on PC's) you will find UNIX very familiar. The main difference is that each UNIX file has an owner and a group that it belongs to, as well as a set of permissions which determine who is allowed to read, alter or delete, or execute the file.

Unix provides hundreds of useful commands for all sorts of purposes, but it is sometimes difficult to find the specific command you are looking for. The total number of Unix commands is immense. No normal user or system administrator would ever need to know them all.
This little table will show you just what you need to get started on your own unix shell account ( if you haven't had one yet, try to find it in the list of Free unix shell providers ). Not all of these are actually part of UNIX itself, and you may not find them on all UNIX machines.
In this box, I will put only Bash shell commands, as all other major shells can now be considered obsolete.

Two conditions you should always keep in your mind in order to be good "Unixer", are :

1. Unix is case sensitive. That is, there's a difference between upper and lower case characters. The command "ls" will list all files in your directory. If you try to type it as "LS", you'll get an error message.


2. Always Use the `man` command to get more informations about any of these commands. For example, to learn more about "ls" command then type "man ls".

Command	Description
man	Display the reference manual pages
pwd	display current directory and path
ls	list contents of directory (equivalent of DOS DIR)
cd	Change working directory
mkdir	Make a directory
rmdir	Remove directories
cp	Copy files (equivalent of DOS command COPY)
rm	Remove (delete) files
file	Determine file type
mv	Move and rename files
vi	Text editor
cmp	Compare two files
ln	Make a file link
find	Walk a file hierarchy
passwd	Change password
which	Locate a program file in the user's path
whereis	Locate programs
gcc, g++	GNU project C and C++ Compiler
gdb	The GNU Debugger
less	View the contents of a text file
diff	Find differences between two files
chmod	Change file modes
ispell	Interactive spelling checker
biff	Be notified if mail arrives and who it is from
lpr	Print a file
lpq	Show the print queue
ftp	Transfer a file to another Unix system
chmod	Change file modes
quota	Display disk usage and limits
alias	Create a command alias
unalias	Delete a command alias
export	Set an environment variable
script	Record your terminal session to a file
bg	Send a job to the background
fg	Bring a job to the foreground
jobs	display a list of current jobs
ps	Show the status of processes
kill	Stop a running processes
history	Display a list of recent commands
logout	end terminal session

Tips & Info :

If the BackSpace key doesn't backspace, try the Delete key, the most common key for fixing types. This key deletes the most recent character you typed, and in most cases removes it from the screen. Unfortunately this key is the most complex, because there is confusion about which key and ASCII code should be used.