This tutorial came about because I wanted to compile my notes from TAFE into a more ordered form so that I could study from them.  I hope you find them useful.


UNIX IS CASE SENSITIVE - This means that it matters whether you type in lower case or upper case. Most commands are in lower case but you will find some special uses of capital letters.

When you connect to the UNIX system you will be asked for your login name and your password - you will be given these by the system administrator when you open your account.

In UNIX you work in a SHELL, which is like a layer in the system. There are parent and child shells. The shell is the program that interprets and executes the commands you type to it.

/bin/bash   is the shell running at TAFE which the students can use (born again shell)
csh (pronounced C shell) is the name of another shell.




USEFUL INFORMATION TO START WITH

man                   manual  (help)
                            press spacebar or  'f '  to scroll down a page
                            arrow keys to go up or down a line
                            'y' to scroll back one line
                            'g' jump back to the start of the file
                            'G' jump to the end of the file

man -h              prints a one line help message on each switch you can use with man

man intro          list of basic system commands
man man           to find out about manual
man ls               to find out about the command  ls
man -k queue    The "man" command will search for the keyword 'queue' and
                        will display all UNIX commands that have that keyword in
                        their short description.

ls --help           for more help on ls  (use this syntax for any command; e.g. rm --help)

q                     quit  -  use to exit many processes including the manual
 

WHERE AM I?

pwd          shows you where you are - Print Working Directory

$               shows you are in parent shell
sh              shell command - now in the child shell
^d             exit child shell - back to parent     (^d means Press Control key and d )

^d             to exit a process - kills shell  (e.g. when using the command 'cat')
                                                                    ('cat' is explained in the next section)
^c             to exit a process - emergency stop  (e.g. if system has stopped)

logout       exit UNIX
exit           exit UNIX
 

BASIC COMMANDS & EXAMPLES

ls              list        (same as dir in DOS)
ls -a          list ALL files, including hidden ones
ls -l           (or ls -long)  long listing  (permissions, owner, size, when last modified)
ls -t           list by time last modified
ls -i           shows all files you have linked (same i-node)
ls -R         list contents of subdirectories
ls -l /etc | grep passwd   - shows long listing of all files with the name passwd in /etc
ls | wc -w    shows how many files in this directory and counts the words

/               root directory
/etc          directory called 'etc'
~              home directory

cd             back to login directory
cd ~          back to your home (login) directory
cd ~dai     go to dai's home directory (if you have permission)
cd ..          up one level
cd /           goes to root directory
cd /bin       takes you to the 'bin' directory

cal             calendar
date           gives time and date

cat             Concatenates or joins files and prints to the screen.
cat  /etc/passwd  -  gives a list of all users on system.
                 When used with a ">", it can join or concatenate multiple files.
cat file1 file2 > file3    appends file2 to the end of file1 and saves it as file3.
cat > myfile   -  will copy nothing to myfile (deletes what is there), OR
cat > myfile   -  like COPY CON in DOS, creates myfile and then you add content,
                        ^d to finish.

cp        copy
cp  /pub/prac/red  ~/red   copy /pub/prac/red  to a file called  red  in my directory

mv        rename or move a file or directory

rm        delete file - UNIX doesn't give you a second chance - delete means delete...
rm -i     gives you a chance to change your mind - do you really want to delete


  this file? But once the file is deleted you can't get it back.

rmdir    delete directory

rm -r  /chicken      If a directory still has files in it, you can get rid of
             the files by using this command, which will remove all
            files and directories in /chicken, and then will remove
             the directory /chicken itself
Be very careful when using rm -r as it removes everything in the directory

mkdir                      make a new directory (can only do this in your own home directory)
mkdir myname         makes a new directory, myname
mv red myname       moves the file red into the myname directory
mv myname green    changes the name of the myname directory to green

'        '              Use to enclose strings when commands contain characters UNIX gives
                        other meanings to  -  e.g. $  ^

grep                  Looks for patterns  (print lines matching a pattern).
                       A powerful search command.
grep '^abe…$'  /etc/dic     Shows all words starting with (^) abe and 3 (…) other letters
                         $ is the terminator (can leave off $ - means finish at the end of the line)
grep '^abe'  /etc/dic  - shows all words starting with abe, any number of letters.
grep '……………$' /etc/dic > fifteen     Send all words with 15 or more letters (shown
                         by the fifteen dots)  to a file called fifteen  (leave off the ^ to mean 15+)

grep  $LOGNAME  /etc/passwd  > myrecord     Searches for the word that is your login name
                         (LOGNAME) in the password file, and sends every line containing that
                         word in the password file to a new file it creates, myrecord  (if myrecord
                         does not exist).

grep blue myfile  This searches the file myfile for the string 'blue' and displays
                          each line containing the word or phrase on your screen.

wc                    word count  (gives number of characters (bytes), words and lines in a file)
wc myfile          prints 3 numbers - the number of lines, words and characters in myfile
wc -l  myfile      number of lines in the file 'myfile'
wc -w  myfile    number of words in the file 'myfile'
wc -c  myfile     number of characters in the file 'myfile'

passwd             to change your password
 

PERMISSIONS  -  Unix is a multi-user system, and so it needs to be very secure.
                            You must have permission to use files belonging to other users.

Following are the numbers and letters you can use in commands to change the mode of a file  (chmod)

read = 4                        owner/user  - u
write = 2                       group          - g
execute = 1                   others          - o
                                     all               - a
 
        4, 2 & 1 are octal digits  (can add them up in order of owner, group, others
        instead of writing u, g, or o  -  see  chmod)

For a file,           read  means read or copy
                           write  means write or change
                           execute  means execute or run the program or shell script

For a directory,   read  means the user can use ls to obtain a listing
                            write  means the user can delete files or add them
                            execute  means they can cd into that directory, but cannot
                                   make a listing unless they have read privileges as well

chown             change ownership of a file or directory  (only ones YOU own)

chown -R        changes ownership of files in subdirectories as well

chown dai myfile       this gives ownership of 'myfile' to dai

A better way of doing this is to give dai read privileges so that he can copy it to his
own directory. With chown the file is still kept in your original directory.

chmod             change mode of a file - can give others read, write or execute privileges

chmod [ugoa]+-[rwx] filename      -      syntax for chmod command

+    adds attributes to a file or directory     e.g.  chmod +x red
-     takes attributes away from a file or directory   e.g. chmod -wx red

chmod +x red    gives everyone execute privileges for red  (could type chmod 111 red)

chmod a+r *.pub  -  This gives everyone (a)  permission (+)  to read (r)  files
                               with the extension   ". pub"

chmod u+rwx red     gives user (owner) all privileges (read, write and execute) for red

chmod 666 passwd    gives read (4) and write (2) privileges to all three groups for the passwd file

Example of long listing:   -rw-r--r-- 1 root root 11563 May 14 11.19 passwd

'- '           at beginning means it is an ordinary file
' d '          at beginning would mean it is a directory
rw-         owner privileges (read, write, not execute)
r--           group privileges (read, not write, not execute)
r--           others privileges ( read only)
1             links  (how many names the file appears under)
root         owner
root         group
11563     size of file
May 14   date
11.19      time
passwd    filename

grep  '^…..$'  /etc/dic | rev | sort | rev > mystery   - finds all the 5 letter words (^…..$)
                         in /etc/dic,  arranges them by the last letter (rev),  i.e. peace becomes
                         ecaep, then sorts them (sort) in reverse order (rev) - word is written right
                         way, but sorted by last letter, then second last, and so on, and sends the
                         results to a file called mystery

     |    pipe        A process.   Directs output from one process/program/command to
                        another process/program/command.
                        Can use the output of one command as input to the next command.

ls -l | grep '^d........x'   This command gives a long listing of all the directories (d) in
                         the current directory for which other users (the x only covers the last
                         grouping of three dots) have execute permission (x).   The expression
                         is quoted to prevent the shell interpreting the ^ metacharacter.

ls -l /dev | more     Shows a list of all terminals being used, a page at a time - find your
                        terminal number (in the following example it is ttyp7) with this command,
                        and can then type a command to stop other users writing to your screen :

chmod  600  /dev/ttyp7     This makes your terminal (/dev/ttyp7) read only for as long as you
                                       are logged on (using the octal digits instead of r--r--r-- or a-wx)

Note:

tty  or  ttyp means teletypwriter  -  it is now used to mean terminal




WRITING MESSAGES TO OTHER USERS

write username    e.g. write dai  (whatever you write appears on dai's screen)
^c                  to go back to prompt (and stop writing messages…)
mesg  n          to stop messages coming in
mesg  y          to receive messages again
 

MORE COMPLEX COMMANDS & EXAMPLES

du                 shows disk usage - size of files or directories - in kilobytes
du -b red      shows how many bytes in the file 'red'
        -a         all
        -c         total
        -l         count links
        -s        summarise  (doesn't break down into subdirectories)
        -S        separate directories - count directory, not including  the size of sub-directories

uniq               to identify duplicates

sort                sorts files

  .  (dot)         current directory

cp /etc/passwd .    copies  passwd  file to current directory

sort mypass | uniq > uniqpass      takes out the duplicate lines from mypass and
                                             copies the file without the duplicates into uniqpass
sort mypass | uniq -d > duplicpass   puts the duplicate lines into the file duplicpass

sort  .bash_history | wc -l   shows how many lines are in your history file

tr                   translates,  e.g. can translate lower case to upper case
tr a-z A-Z < /etc/group > groups   - copies the file /etc/group to groups in the current
                      directory and capitalizes the contents

cut                 cuts out a section you specify from a file
cut  -c  1-4  /etc/passwd  > four   - creates a file called four which has a list of the first
                      four letters of each entry in  /etc/passwd

grep 100  /etc/passwd | cut -f  5  -d : | sort    finds all entries in the password file with
                      100 anywhere on the line, sorts alphabetically by field 5 (user name)

grep              finds a pattern
100                the pattern is any line with 100 in it
 /etc/passwd  the name of the file you are searching
| cut               send the results to cut
-f                   cut looks for a field
5                    field number 5
-d                  delimiter - the next character shows where a field starts
:                    this shows how to tell where a field starts
| sort              sends the output to sort, which sorts alphabetically or numerically

more      1.  use in front of the file name you want to view - shows you the contents
                  of a file, a page at a time  (very useful if you want to view a long file)
              2.  use with | (pipe)  after a command (as in DOS)
 
                   while viewing a file with  more can move to the next page by using:
                      spacebar or f      to scroll a page at a time
                       <enter>             to scroll results a line at a time
                           q                    to quit

man more                         get help on using 'more'.  Can also get help by pressing '?'
                                        from within a 'more' screen
sort /etc/passwd | more     Shows all entries in passwd file, a page at a time

more myfile                       Displays the contents of "myfile" a page at a time

more myfile red blue          Displays the contents of each of these three files, one after the other,
                                         a page at a time

"more" doesn't let you go backwards; see the command "less"

less               is an advanced version of more. In addition to the commands
                     given for 'more'  less adds:
 
          y         To scroll back one line.

          g         Jump back to the start of the file.

          G        Jump to the end of the file.

Both  more  and  less  offer the ability to search for words in the file, using  '/ '

If you want to scroll forwards to some particular word, type a forward slash (/) followed by the word you want; for example, to search for the word "computer" while viewing a document with more or less, type  /computer and <enter>

head filename      Lists the first 10 lines of a file
head -25 myfiles  Shows the first 25 lines of myfile

tail filename         Lists the last 10 lines of a file
tail -5 myfile        Lists the last 5 lines of the file 'myfile'
tail +25 myfile     All but the last 25 lines will be displayed of myfile

touch         change the file time stamps to the current time
touch red   changes date and time of  'red' file to current date and time
touch red -d 06:00    changes date of  'red' to current, and time to 6.00
touch 06081200 red  changes the date of red to Jun 8 and the time to 12.00
        -m     change modification time only
        -a      change access time only
        -t       use the argument MMDDhhmm[[CC]YY][.ss] instead of current time

(      )  or   '        '        can give more than one command on a line, inside brackets
                                   or quote signs separated by a semi-colon

(sleep 10; date) &      Using the & makes the commands inside the brackets run as a
                 background process, so you get the $ command prompt back straight
                 away (after 10 seconds the date will come on the screen)

                [1] 5541 (can be any number) will appear after this command - this is
                 the process identification number (PID):

kill 5541    this will kill the process, and you go back to the prompt.

ps              shows which processes are running for you (all windows, the desktop
                  menu, the clock, etc).
ps -a          shows others processes as well as your own
ps -u          shows the user name of the processes that are running
ps -x          shows process status of every process which belongs to the operating
                  system (daemons)

ps -ef | grep username     The result will be all the processes running for username.
                 For example, for user dai, the numbers 5577, 5544, etc,
                 are process identification numbers (PID):
 
       dai  5577  5576  2 18:23:14 pts/2    0:00 -csh
       dai  5544     1  0 18:19:54 ?           0:00 /usr/bin/X11/xterm -geom 80x24+17-17
       dai  5543     1  0 18:19:54 ?           0:01 /usr/bin/X11/toolchest -name ToolChest
       dai  5590     1  0 18:23:26 ?         10:36 /tools/bin/netscape3.0
       dai  5884  5559  0 21:27:37 pts/1    0:02 nedit lab5_96.html




LINKS

ln              gives two paths to the same program, e.g.  ln ksh sh (can call it either
                 ksh or sh)




ALIASES

Aliases are abbreviations for commands or sets of commands. This feature is particularly useful to execute commands or command sequences that you use frequently. In this way you can avoid retyping a command sequence many times during a login session.

alias                    To see the aliases already being used

alias h = 'history'   Entering h will execute the history command

alias l = 'ls -al'       Entering 'l' will show a long listing of all files, including hidden files

unalias h   }         To delete the previous alias definitions
unalias l    }




INFORMATION ABOUT OTHER USERS

w         }
who      }     shows logged in users (login name, terminal line, login time, remote hostname)
rusers   }
who -c        shows whether users allow messages or not  (+ or - after name)

/proc           a file that has process information for currently logged on users

/etc/utmp     temporary user file in the etc directory - information on current users

uptime         shows number of users logged on, and how long the system has been running

finger           Getting more information about other users. The finger command displays
                    information about a specific user. For instance, entering: finger joe lists
                    information available on any user whose username is joe
finger -s       includes write status as well  (if the user will receive messages)
finger -l        gives more information, such as phone number and user's home directory




VARIABLES

set | more      shows environment variables  (initialized when the system is started)

User defined variables

        Example 1

mydog = rover
echo  $mydog
rover                      When shell sees $name it performs variable substitution.

        Example 2

mycat = "big black moggy"   (need " " for a string)
echo  $mycat
big black moggy      (appears on screen)
sh                           (change to child shell)
echo  $mycat          (child shell - my cat does not exist there, so no response)
exit                         (change back to parent shell)
echo  $mycat
big black moggy      (now in parent shell - it shows the variable on the screen)

Parent and child shells do not know each other's variables

Example 3
export mycat          (parent shell)
sh                           (export to child shell)
echo $mycat           (now in child shell)
big black moggy      (response from child shell)
 

CHANGING THE LOOK OF YOUR SHELL

To change prompt, type in     PS1="Yes, Veronica>"    (whatever you want in the "  ")

To change it permanently, every time you login, need to change the   .profile   file

.profile   customises the look of your login shell (it is a hidden file).

To edit your .profile file, type
vi .profile  (see how to use vi  later in these notes)

PS1 = "Yes, $LOGNAME>"  (if you want your login name - or anything else you want there)
echo   Welcome to the UNIX system
who
   users = `who | wc -l`          (` is on the tilde (~) key.  You must use these
                    parameters to enclose command - the result of these two commands is a
                    listing of who is logged on (who) counted by number of lines (wc -l).
                    UNIX knows that users is a variable, because it is followed by = and a string

echo  There are $users users logged on  ($ before the variable name tells UNIX
                    to replace the variable with the string following the = sign.
date

The result of this .profile gives you a welcome screen that says,

            Welcome to the UNIX system
             (shows a list of who is logged on)
            There are (9) users logged on
            Today is (Tuesday 17th June)
            Yes, Veronica>
 
On the other hand, if you want no messages when you log in, you can ask for a quiet login:

> .hushlogin     makes a file called .hushlogin in your directory (you don't need to put anything
                        into the file)   .hushlogin gives a quiet login; no messages, and just the default
                        prompt.
 

PRACTICAL REDIRECTION

There are 3 predefined data streams in UNIX

0  std in       keyboard input by default comes from keyboard
1  std out     screen input by default goes to screen
2  std err     screen error messages by default go to screen

You can attach these data streams to other files or devices - this is called redirection.

>       send out to a file               }
<       take output from a file       }  Redirection  -  only used for FILES
>>     append to a file                 }
2>     send errors to a file           }

who > who.out   sends the output of the who command to a file, who.out
sort < who.out    takes input from who.out and sorts contents on screen
                            (doesn't change the file)
sort < who.out > who.sort        as above, but sends it to a new file instead, who.sort
 

UNIX treats all devices as part of the file system.  They all live in  /dev
e.g.  /dev/fd0   (floppy disk drive 0)               /dev/hda1   (hard disk drive 1)

ls -l /dev   to get a listing of all devices - the first letter in the listing is b (block) or
                     c (character)
A keyboard is character oriented  (deals with a character at a time)
FDD and HDD are block oriented  (deal with chunks of data)

crw-rw-rw-  1  root  0, 0  Sep 27  23:09  console
crw-rw-rw-  1  bob  1, 0  Sep 28  02:30  tty0
crw-rw-rw-  1  root  3, 2  Sep 27  23:15  null  ( where 3 = major device number and
                                                                                       2 = minor device number )
/dev/null      is a bit bucket - a black hole  (data goes in but never comes out…)

find  /home  -name  myfile  -print  2> /dev/null    There will be masses of error messages
                    because find will search even directories which you don't have executable
                    rights     over. You will now see only the listings of myfile on the screen.

find            find
/home         start search from the /home directory downwards
-name         the next word is the name of the file I want to find
myfile         name of file I want
-print          show it on the screen
2>              redirects errors somewhere else..  (to screen by default…)
/dev/null     send the error messages to the black hole

find  /home  -name  myfile  -print  2> err.log     same command, except that the error
                                    messages are sent to a file,  err.log
 
 
WILD CARDS

*               matches any character any number of times
?               matches a single character
[a-f]          match any character in range a - f

cp /etc/* .       copy all files in  /etc directory to current directory
ls b*               list all files starting with b
rm c????        remove all files starting with c and having 5 letters
rm d [aeiou]*  remove all files starting with d and having a,e,i,o,u for the second letter
ls d[^g-o]*      list all files starting with d, but NOT the ones with g to o as second letter
 

SHELL SCRIPTS    (like batch files in DOS)

script               records all interactions in a window and saves in a file.
script nu          write your script to a file called  nu.   To stop recording, use Ctrl-D.
 
Alternative way to make shell scripts:
cat > nu           makes new file called 'nu'  (like copy con in DOS)
who | wc -l       input into nu
^D                   end of input - closes file
 
running the shell script:    when you type nu it runs the command who | wc -l
                       and gives the result  9  (if there are 9 users logged on)
 

VI   EDITOR - USE TO EDIT FILES

vi passwd         opens the passwd file for editing.  Type a filename after vi or it opens an empty file.

man ls > ls.out   copies the manual for ls to a file called ls.out
vi ls.out             can then edit the manual for ls in your file

a    append - inserts text after the cursor }  automatically puts you in edit mode -
i     insert  - inserts text before the cursor}  whatever you type  now will be put in
o    open   -  inserts text in the next line   }   your file

            <ESC>    puts you in command mode

h         move one place left       (9h moves 9 characters to the left)
l          move one place right     (9l  " "        right)
j          move one place up         (9j " "        up)
k         move one place down    (9k " "        down)
Arrow keys can also be used, but only in command mode

w        forward one word
b         back one word
e         end of the current word
 

$         moves to end of line
0 or |   moves to beginning of line
G        moves to end of file
nG      moves to line n; e.g. 12G jumps to line 12
^         first non-whitespace character in the line
{         back one paragraph
}         forward one paragraph
 t         to   (e.g. tx places the cursor a character before the next x on the same line)
/word  moves to the next word after the /
            (e.g. /And moves to the next And in the document)


r          replace character under cursor
x         delete character under cursor
dw      delete a word  -  e.g.  5dw  deletes next five words
dd       delete a line    -  e.g.   9dd   deletes next 9 lines
d$       deletes to the end of the line
dG      delete to the end of the file
d |       delete to the beginning of the line
d2G    delete to the second line of the file
d{       delete to the beginning of the paragraph
dtx       deletes from the cursor to the next x

cw      changes the current word  (like highlighting the word and typing over it)
c4w    changes the next four words
c}       changes the rest of the current paragraph
cc       changes the current line

u         undo the last change to a line
U        undo all changes to the line - restore to original state

<ESC>  :  wq      write file and quit
<ESC>  :  q!       quits without saving
<ESC>  :  w newfilename     substitute your file name for newfilename if you have
                                                opened  vi  without using a name for your file
 

WHAT COMMANDS HAVE I USED?

history       lists previous commands by number.

After you have found the command number you want to repeat, type:

       !n       executes the nth command

       !!        executes the last command

Can also use the up and down arrows to see previous commands, and press enter to execute it again (as in DOS using doskey)
 

HIDDEN (invisible) FILES

All invisible files have names that start with a " . " (dot) and are also referred to as dot files. They are called invisible because they are not normally displayed in a directory listing. In other words when you issue the command ls in a UNIX shell, dot files are not displayed. To see all of your files use the -a switch: ls -a
 
There are several important default hidden files in your home directory:  the  . (dot),  .. (dot dot),  .login,   .cshrc,   .user,      .profile

The system uses the . and .. files to connect to the current directory (.) and its parent directory (..)
The .login file contains commands that UNIX will execute every time you login to your account.
 

DIRECTORIES

            There are some standard names for UNIX directories and subdirectories based on
            the purpose of the directory.

/bin    -  normally contain executable programs
/man  -  manual pages are stored in man directories
/doc   -  miscellaneous documentation is frequently found in a doc directory
/lib     -  the lib directories hold libraries of various procedures and functions that
                    can be used when writing a program, such as special constant, function,
                    and procedure declarations for use in C programs
/src    -  directories for storing source code are usually named src
/tmp   -  directories named tmp are usually for temporary storage of files
 
 

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