Unix Operating System: 1 STC Technologies

Unix Operating System
STC Technologies
What is UNIX?
Operating system developed in 1960s.

Multi-user and multi-tasking system.
Made of three parts : Kernel, Shell and
programs.
Everything in UNIX is either a file or a process.
A process is an executing program identified
by a unique PID.
A file is a collection of data.
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Components of UNIX
Hardware
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Shell as an Interpreter
The shell is an ordinary program which interprets the commands
that are typed at the terminal, and translates them into commands
that are understood by the kernel.
These programs are located in individual files in one of the system
directories, such as /bin, /etc, or /usr/bin.
The process of command interpretation by the shell can be
explained as follows:
Reads the command
Searches for and locates the file with that name in the directories
containing utilities.
Loads the utility into memory
Executes the utility
Shell scripts of files with program like commands and structures which is
executed in a shell which normally end with .sh extension
Listing files and directories

Command
ls
ls -a
list files and directories

list all files and directories
match any number of characters
match one character
man command
whatis command
mkdir
Meaning
read the online manual page for a

command
brief description of a command
make a directory
cd directory
change to named directory
cd
change to home-directory
cd ~
change to home-directory
cd ..
change to parent directory

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More File Commands

Command
cp file1 file2
copy file1 and call it file2
mv file1 file2
move or rename file1 to file2
rm file
rmdir directory
remove a file
remove a directory
cat file
display a file
less file
display a file a page at a time
head file
display the first few lines of a file
tail file
display the last few lines of a file
grep 'keyword' file

6
Meaning
search a file for keywords

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Redirection and Piping

Command
Meaning
command > file
redirect standard output to a file
command >> file
append standard output to a file
command < file

command1 |
command2
redirect standard input from a file

pipe the output of command1 to the input of
command2
cat file1 file2 > file0 concatenate file1 and file2 to file0
sort
sort data
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vi (visual editor) and its Commands
Default editor for UNIX.

It is a full screen editor.
Two modes of operation:
Command - causes action to be taken on files.

Insert - entered text is inserted into the file.
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Entry and Exit
To start vi :
Command
vi filename
vi -r filename
To exit vi :
Command
:x<Return>
:wq<Return>
Meaning
edit filename starting at
line 1
recover filename that was
being edited when system
crashed
Meaning
quit vi, writing out modified file to
file named in original invocation
quit vi, writing out modified file to
file named in original invocation
:q<Return>
quit (or exit)
:q!<Return>
quit vi even though latest changes

have not been saved for this vi call
vi
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Cursor Movements
Command
or
<Return>
[or down-arrow] move cursor down one line
[or up-arrow]
or <Backspace> [or leftarrow]
k
or
<Space>
0
move cursor up one line

move cursor left one character
[or right-arrow] move cursor right one character

(zero)
$
move cursor to start of current line

(the one with the cursor)
move cursor to end of current line
:0<Return> or 1G
move cursor to beginning of next word

move cursor back to beginning of
preceding word
move cursor to first line in file
:n<Return> or nG
move cursor to line
w
b
:$<Return> or G
10
Meaning
move cursor to last line in file

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Screen Manipulation
Command
^f
^b
^d
^u
^l
^r
11
Meaning
move forward one screen

move backward one
screen
move down (forward) one
half screen
move up (back) one half
screen
redraws the screen
redraws the screen,
removing deleted lines
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Inserting or Adding Text

Command
u
i
I
a
A
o
O
12
Meaning
UNDO WHATEVER YOU JUST DID; a simple

toggle
insert text before cursor, until <Esc> hit
insert text at beginning of current line,
until <Esc> hit
append text after cursor, until <Esc> hit
append text to end of current line, until
<Esc> hit
open and put text in a new line below
current line, until <Esc> hit
open and put text in a new line above
current line, until <Esc> hit
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Changing Text
Command
r
R
cw
cNw
C
cc
Ncc
13
or
cNc
Meaning
replace single character under cursor (no <Esc>
needed)
replace characters, starting with current cursor
position, until <Esc> hit
change the current word with new text,
starting with the character under cursor, until
<Esc> hit
change N words beginning with character under
cursor, until <Esc> hit;
e.g., c5w changes 5 words
change (replace) the characters in the current
line, until <Esc> hit
change (replace) the entire current line, stopping
when <Esc> is hit
change (replace) the next N lines, starting with
the current line,
stopping when <Esc> is hit
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Deleting Text
delete single character under cursor
delete N characters, starting with

character under cursor
delete the single word beginning
with character under cursor
delete N words beginning with
character under cursor;
e.g., d5w deletes 5 words
delete the remainder of the line,
starting with current cursor position
Nx
dw
dNw
D
Ndd
14
dd
delete entire current line
or
delete N lines, beginning with the

current line;
e.g., 5dd deletes 5 lines
dNd
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Cutting and Pasting Text

yy
Nyy
or
p
15
yNy
copy (yank, cut) the current line into

the buffer
copy (yank, cut) the next N lines,
including the current line, into the
buffer
put (paste) the line(s) in the buffer into
the text after the current line
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Searching Text
16
/string
search forward for occurrence of
?string
search backward for occurrence of
string
in text
string
in text
move to next occurrence of search string
move to next occurrence of search string in

opposite direction
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Determining Line Numbers
:.=
:=
^g
17
returns line number of current line at bottom of

screen
returns the total number of lines at bottom of
screen
provides the current line number, along with the
total number of lines,
in the file at the bottom of the screen
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Saving and Reading Files
:r filename<Return>
:w<Return>
:w newfile<Return>
:12,35w smallfile<Return>
:w! prevfile<Return>
18
read file named filename and insert after

current line
(the line with cursor)
write current contents to file named in
original vi call
write current contents to a new file named
newfile
write the contents of the lines numbered 12

through 35 to a new file named smallfile
write current contents over a pre-existing
file named prevfile
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File system security (access rights)
19
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Changing access rights

Command
Meaning
ls -lag
list access rights for all files
chmod [options] file
change access rights for named file
Symbol
20
Meaning
user
group
other
all
read
write (and delete)
execute (and access directory)
add permission
take away permission
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Processes and Jobs

Command
Meaning
command &
run command in background
^C
kill the job running in the foreground
^Z
suspend the job running in the foreground
bg
background the suspended job
jobs
fg %1
foreground job number 1
kill %1
kill job number 1
ps
kill 26152
21
list current jobs
list current processes

kill process number 26152
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Environment Variables
USER (your login name)

HOME (the path name of your home directory)
HOST (the name of the computer you are
using)
ARCH (the architecture of the computers
processor)
DISPLAY (the name of the computer screen to
display X windows)
PRINTER (the default printer to send print
jobs)
PATH (the directories the shell should search
to find a command)
22
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Shell Variables
pwd (your current working directory)

home (the path name of your home directory)
path (the directories the shell should search to
find a command)
prompt (the text string used to prompt for
interactive commands shell your login shell)
23
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What is a Shell Script?
A Text File
With Instructions
Executable
What is a Shell Script?

$ cat > hello.sh <<MY_PROGRAM
#!/bin/sh
echo Hello, world
MY_PROGRAM
$ chmod +x hello.sh
$ ./hello.sh
Hello, world
NB: The two lines of code can be created through vi editor as well
What is a Shell Script? How To Run

#!/bin/sh
echo Hello, world
MY_PROGRAM
$ chmod +x hello.sh
$ ./hello.sh
Hello, world
What is a Shell Script? What To Do

#!/bin/sh
echo Hello, world
MY_PROGRAM
$ chmod +x hello.sh
$ ./hello.sh
Hello, world
What is a Shell Script? Executable

#!/bin/sh
echo Hello, world
MY_PROGRAM
$ chmod +x hello.sh
$ ./hello.sh
Hello, world
What is a Shell Script? Running it

#!/bin/sh
echo Hello, world
MY_PROGRAM
$ chmod +x hello.sh
$ ./hello.sh
Hello, world

Unix Operating System: 1 STC Technologies

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Unix Operating System

Operating system developed in 1960s.

Listing files and directories

list files and directories

match any number of characters

match one character

read the online manual page for a

change to named directory

change to parent directory

More File Commands

copy file1 and call it file2

move or rename file1 to file2

display a file a page at a time

display the first few lines of a file

display the last few lines of a file

grep 'keyword' file

search a file for keywords

Redirection and Piping

command > file

redirect standard output to a file

command >> file

append standard output to a file

command < file

redirect standard input from a file

vi (visual editor) and its Commands

Default editor for UNIX.

Command - causes action to be taken on files.

Entry and Exit

quit (or exit)

quit vi even though latest changes

[or down-arrow] move cursor down one line

move cursor up one line

[or right-arrow] move cursor right one character

move cursor to start of current line

move cursor to beginning of next word

move cursor to line

move cursor to last line in file

move forward one screen

Inserting or Adding Text

UNDO WHATEVER YOU JUST DID; a simple

delete N characters, starting with

delete entire current line

delete N lines, beginning with the

Cutting and Pasting Text

copy (yank, cut) the current line into

search forward for occurrence of

search backward for occurrence of

move to next occurrence of search string

move to next occurrence of search string in

Determining Line Numbers

returns line number of current line at bottom of

Saving and Reading Files

read file named filename and insert after

write the contents of the lines numbered 12

File system security (access rights)

Changing access rights

list access rights for all files

chmod [options] file