UNIX operating system Quick Reference
% alias lu 'ls -u'
% lu
ALT-H presents a summary of special keys
cat - > temp
CTRL d
The cat utility can also be used to join many files together into a single file. The command,
cat temp .profile > temp1
cp * /usr/tmp
would copy all the files in the current directory to the directory /usr/tmp.
head -2 temp
would list the first 2 lines of the file temp on the console.
tail -2 temp
This is used to view the last few lines of a file
lp temp
This command is used to obtain a hard copy printout of a file. ONLY type this command IF a
printer is attached to the computer system.
pr (print)
The print utility prints the file to stdout. The switches it accepts are
-ln set page length in lines to n
-wn set line length in characters to n
-n number output lines
-t do not print page header or trailer
-digit number of columns to use
+digit start at page number
pr -2 -n temp
This prints the file temp to stdout, using two columns per line, numbering each line.
who -u
mesg (message)
This command permits or denies messages invoked using write. The switches it uses are -y and -n
news
The news command keeps the user informed of current events.
grep 'change' temp
The grep command searches a file for a pattern. The following command
searches the file temp in the current directory for the text string change. Using the * wildcard
specifies all files, and using the switch -n will display on which line the text string is found.
time ls -la
This command times how long it takes to execute a given command. Type the command,
The man command can also accept the following names as switches.
ADM System Administration
C Commands
M Miscellaneous
F File Formats
HW Hardware Dependent
S Subroutines and Libraries
CP Programming Commands
DOS DOS Subroutines and Libraries
LOCAL Local utilities for your system
An example command which calls up the reference section on 'Miscellaneous features' is (this may
not apply to all UNIX systems).
man M
mv temp temp2
The mv command is used for moving or renaming files. Type the command
pwd print current working directory
cd change directory
mkdir make a subdirectory
rmdir remove a subdirectory
Typing the set command will print out a list of all the current shell environments. This is a list of all
the variables and settings that the shell currently has.
The majority of these are loaded when you first log in. The first thing the shell does is execute the
file .profile in the users home directory!
Type the command,
set
shell variables
The shell supports user and system variables. An example of system variables are,
PS1 system prompt
PS2 secondary line shell prompt
HOME home directory
LOGNAME login name
Variables are assigned values using the = sign.
PS1="Hi there : "
dir="ls -la"
$dir
sample="Hello world"
echo $sample
A secondary copy of the shell is invoked by typing
sh
The secondary shell is terminated by typing exit.
Another feature of UNIX is running processes in the background. When a command is appended
with the & symbol, it is run in the background and the shell prompt immediately returns.
Each process in UNIX is identified by a PID (process identification number). When a
background process is started off, UNIX will print its PID number in square bracket
ls -l > dirlist&
NOTE that the shell prompt immediately returns, and a number in brackets is printed. The &
character signals to the shell that the command is to run in the background.
2868
sleep 200&
vi command
k up
j down
h left
l right
a appends to the last line of the file
i inserts at the current cursor position
o inserts one line down from the current cursor position
O inserts one line up from the current cursor position
x erase the character at the cursor
r replace the character at the cursor
dd delete the entire line where the cursor is
The u command undoes the previous command.
The U command undoes all the changes made on the current line.
You are strongly encouraged to save editing changes regularly. The command to write the editor
buffer is
:w
If you decide that you do want to over-write the existing file, but rather save the changes to a new
file, then follow the :w command with the name of the new file,
:w newfile2
ZZ writes the buffer to disk into the original file, then returns to the shell
:wq same as ZZ
:q! quits the editor, abandons the buffer, and returns to the shell
b move the cursor to the beginning of the previous word
e move the cursor to the end of the next word
0 move to the beginning of the line (zero)
$ move to the end of the line
ctrl-d scroll down
ctrl-u scroll up
3000G goto line 3000
To position the cursor at the last line in the file, type
G
To position the cursor at the beginning of the file, type
1G
ctrl-g display current line number
Searching
/ indicates a search forward
? To search backwards
n will search forwards for the next occurrence.
dw command deleted the current word.
The dd, cc, and yy commands affect the entire line.
The temporary buffers are numbered 1 to 9,
the buffer number preceded by a double quote ( "np ).
There are 26 named buffers for use by the yank command. These buffers are named 'a' to 'z'.
"ay} yank from cursor to end of paragraph into buffer a
thus the following command moves lines 1 to 3 to the end of the file.
1,3m$
ps list processes
kill kill a process
& run a process in the background
The system call is accessible as a set of 'C' functions, as the majority of UNIX is also written in
'C'. Typical system calls are,
_read for reading from the disk unit
_write for writing to the disk unit
_getch read a character from a terminal
_putch write a character to the terminal
_ioctl control/set device parameters
Reserved IP Addresses
The following IP addresses are reserved for special purposes, and must NOT be assigned to
any host.
Network Addresses : The host portion is set to all zero's
(129.47.0.0)
Broadcast Address : The host portion is set to all one's
(129.47.255.255)
Loopback Addresses : 127.0.0.0 and 127.0.0.1