1. Introduction to Unix
Developed by Ken Thompson and Ritchie originally in assembly, and later in C, thus making it portable to other machines.
It is an operating system.
It acts as interface between user and hardware.
The main feature of Unix is "open system".
Supports multi user and multi task features.

2. Components of UNIX SHELL:
Computer understands the language of 0's and 1's called the binary language.
The Shell is an special program that takes in the human understandable command and if it is an valid one it will pass on to the Kernel for execution.
KERNE:
The Kernel is the heart of the system. It contains a set of programs normally written in C to communicate with the hardware.
The Kernel acts as the interface between the computer hardware and various programs/application/shell.

3. Unix File System In Unix each and everything treated as a file
The normal file known as Regular file
The directory file known as directory file
The device file known as device file
The base of the Unix file system is "/" (called as root) and also it is administrative directory

4. Unix File System
/bin - It maintains all the user executable commands. (ls, rm ..)
/etc - It contains all system configuration files. (unlink, cron ..)
/etc/password - It contains each and every user information with 7 fields
/dev - It contains all device files. (ip, log..)
/tmp - Stores all temporary files information
/sbin - It contains all administrative executable commands. (uname..)
/lib - It contains all library files information
/home or /usr - It is users home directory

5. Login Process login: venky password: ***** It will display the prompt
$ - User working prompt
# - administrator working prompt

6. logname pwd date clear cal cal 2015 cal 03 2015 uname uname -rhostname
Basic Commands
logname
pwd
date
clear
cal
cal 2015
cal
uname
uname -rhostname

7. Basic Commands hostname -i who finger username who am i uptime
su - username
whoami
which
exit
man commandname

8. Files Creation
cat - It is used for creating new files (or) to open existing files (or) to append data to the existing file
cat > filename --> To create a file
cat filename (or) cat < filename --> To open a file
cat >> filename > To append data to a file
cat file1 file2 file3 .. filen
touch - To create empty file and to change the time stamp
touch filename
touch file1 file2 .. filen
cat > .filename --> creating hidden files

9. Files Deletion rm filename - to delete file
rm -i filename - to get confirmation before deleting
rm -f filename - to delete a file forcibly
rm file1 file2 file3 - to delete multiple files

10. Working with directories
mkdir - To create new directory
Syntax: mkdir directoryname
mkdir dir1 dir2 .. dirn
mkdir abc xyz abc/a1 abc/a2 abc/a1/a11 abc/a1/a12 xyz/x1 xyz/x2
mkdir .dirname --> to create hidden directory
cd dirname
cd to come out from current working directory
cd / -- root directory
cd o cd ~ -- to come to user's home directory

11. Removing Directories rmdir - To remove directory rmdir dirname
rmdir -r dirname --> To delete recursively
rmdir -ri dirname
rm -rf dirname --> To delete recursively entire directory with forcibly

12. Copy cp - To copy a file or directory Syntax: cp sourcefile targetfile
cp -i file1 file2
cp abc/a1/a11/emp xyz/x1
cd abc/a1/a11
cp emp ../../../xyz/x1
cp file1 file2 .. filen directory
cp emp a1 sample abc
cp -R sourcedir targetdir
cp -R abc xyz

13. Move mv - To rename or to move file/directory mv file1 file2
mv dir1 dir2
mv emp .emp --> to hide existing file
mv .emp emp --> to unhide a file
mv .abc abc --> to unhide a directory

14. Viewing list of files
ls - list current directory files and sub directories
ls -a - list all files along with hidden files
ls -r - reverse order
ls -R - list all files recursively
ls -t list files based on date & time

15. Wildcard characters * - It matches 0 or more characters
? - It matches any single character
[] - It maintains any single character in the given list
[-] - It matches any single character in the given range
ls t*
ls *s
ls b*k
ls a?
ls [bkn]*
ls [a-h]*
rm *
cp abc/a1/a11/* xyz/x1

16. Count lines, words and characters
wc - It is the command which gives number of lines, words and characters in a given file
wc filename
wc -l filename --> counts no of lines
wc -w filename --> counts no of words
wc -c filename --> counts no of characters
wc -lw filename --> counts no of lines and words

17. Compare, diff, comm and file
cmp - It compares 2 files character by character, if no output, then files are same otherwise the files are not same.
cat > a1
hello
cat > a2
helo
diff - It displays different lines between 2 files
diff file1 file2
comm - It displays common lines between two files
file - It displays he type of file whether it ASCII text file (or) empty file (or) directory

18. Redirecting Input/Output/Errors
stdin(0) < --> Redirect Input
stdout(1) > (or) 1> --> Redirect Output
stderr(2) 2> --> Redirect Errors
cat emp > file1
cta sample 2> file2
cat file1 file2 file3 > out_file 2> err_file

19. Filters - grep
grep [Globally search a regular expression and print it]: It is used for to search a string in a file or files
syntax: grep pattern filename(s)
grep hi sample
grep hello sample
grep hi a1 a2 a3 --> It will search hi in a1, a2 and a3 files
grep hi * --> It will search hi in all files
grep "hello world" sample
grep -i "Hello" sample --> It ignores the case sensitive

20. Filters - grep
grep -c "hi" sample --> counts no of lines having "hi"
grep -n "hi" sample --> It displays line numbers containing "hi" word
grep -v "hi" sample --> It display other than "hi" string lines
grep "h*" sample
grep "b[aeiou]" sample --> displays lines which are having ball, bill, bell, bull, etc
grep "b..d" sample --> displays band, bond, bird, b12d, etc

21. Filters - grep Word pattern characters:
\< \> --> word boundary
\< --> start of the word
\> --> end of the word
grep "\<hi\>" sample
grep "\<hi" sample
grep "hi\>" sample
grep "\<[0-9][0-9][0-9][0-9]\>" sample

22. Filters - grep Line pattern characters: ^ --> start of the line
$ --> end of the line
grep "^h" sample --> displays lines starting with "h"
grep "^the" sample --> displays lines starting with "the" characters --> there, the, etc
grep "^\<the\>" sample --> displays lines starting with "the" word only
grep "o$" sample --> displays lines ends with "o"
grep "[0-9]" sample --> It displays lines ends with digit
grep "^[bkt]" sample --> It displays lines stating with b or k or t

23. Filters - grep
grep "^[^bkt]" sample --> displays lines which are not starting with b or k or t
grep "^unix$" sample --> displays lines having only unix
grep "^...$" sample --> displays lines which are having 3 characters
grep "^\." sample --> displays lines starting with "." character
grep "^$" sample --> displays empty lines
grep -c "^$" sample --> counts number of empty lines
grep -v "^$" sample --> display non empty lines
How to remove empty lines in a file?
grep -v "^$" sample > temp
mv temp sample

24. Filters - grep fgrep: It searches multiple strings fgrep "unix"
> oracle
> perl" sample
egrep: will support regular expression
egrep 'Rahma+n' test
egrep 'Google*' google.txt
egrep "(unix | perl)" sample
egrep 'Go{2}gle' google.txt
Cat Pattern
Rahman|sachin
egrep -f pattern Legend

25. Filters - sed sed: It is used to replace a string
syntax: sed "s/oldstring/newstring/g" filename
sed "s/unix/linux/" sample --> replaces unix with linux only on first occurrence
sed "s/unix/linux/g" sample --> replaces unix with linux globally
sed "s/UNIX/linux/gi" sample --> ignore case sensitive
sed "s/^unix/linux/gi" sample
sed "s/^$/hello/g" sample --> empty lines replaced by hello
sed "s/unix//gi" sample --> delete unix word from sample file

26. Filters - sed
sed -n '3p' sample --> displays 3rd line from sample file
sed -n '2,5p' sample --> displays 2nd line to 5th line from sample file
sed -n '$p' sample --> displays last line of sample file
sed -n '2,4p
>7,10p' sample --> displays 2nd to 4th lines and 7th to 1oth lines
sed '3d' sample --> deletes 3rd line from file

27. Filters - tr tr: It translates character by character
tr "a e i o u" "A E I O U" < sample --> takes input from sample and it replaces small vowels with capital vowel character
tr "," "\t" < emp --> In emp file all , characters will be replaces with tab space
tr "[a-z]" "[A-Z]" < sample --> to convert all characters from lower case to upper case
tr "[a-zA-Z]" "[A-Za-z]" sample --> It converts sample file content into reverse case
tr -d "a" < sample --> It deletes 'a' character from sample file
tr -d "a e i o u" < sample --> It deletes vowel characters from file

28. Delimiter
delimiter means field separator. The default delimiter is tab key
entry key means record separator.
cat emp --> here , is the delimiter
101,venky,2000,10
102,chaitu,4000,20
cat emp1 --> here tab is the delimiter
101 Dinesh unix hyd
102 ramesh perl chn

29. cut
cut: It is used to extract required fields and characters from a file
cut -f 2,4 student --> displays 2nd and 3rd fields from student file
cut -f 2-5 student --> displays 2nd to 5th fields from student file
cut -d"," -f 2,4 emp --> displays 2nd, 4th fields from emp file (the delimiter is ,)
cut -c 1-10 student --> displays 1st character to 10th character from student file
cut -c 5-10, student --> displays every line 5th character to 10th character and 15th character to 20th character from student file

30. sort
sort: It sorts the given file contents based on ASCII values in ascending order
Syntax: sort filename
sort -r sample --> sorts in descending order
sort -u sample --> displays unique lines i.e it eliminates duplicate lines
sort -n sample --> sorts based on numeric comparison

31. uniq uniq: It displays uniq lines in the given file.
Syntax: uniq sample
uniq -u sample --> displays non duplicate lines
uniq -d sample --> displays only duplicate lines
uniq -c sample --> it counts how many times the lines are repeated in the file

32. head and tail
head: It displays the first 'n' lines from given file. By default head displays first 10lines.
syntax: head -n filename
head -5 sample --> displays the first 5lines
tail: It displays the last 'n' lines from given file. By default head displays last 10lines.
syntax: tail -n filename
tail -5 sample --> displays the last 5lines
tail +5 sample --> displays from 5th line to last line

33. Piping piping(|): It is used for to combine two or more commands.
count number of users connected to servers
who | wc -l
count number of files in current directory
ls | wc -l
count number of sub directories in current directory
ls -l | grep "^d" | wc -l
display 3rd line to 7th line from sample file
head -7 sample | tail +3

34. File Permissions for file: read --> open a file
write --> write and modify
read & execute --> execute a file
for directory:
read --> ls
write --> create and delete files
read & execute --> cd
user -> u read -> r + -> add permission
group -> g write -> w - -> deny permission
others -> o execute -> x = -> assign permission

35. File Permissions - chmod
chmod: It is used for to change the file permissions
syntax: chmod who/[+/-/=]/permission filename/dirname
chmod g+x sample1 --> It adds execute permission to group members
chmod u+x, g-w sample1 --> It adds execute permission to owner and it removes write permission from group
chmod g=w sample --> It adds only write permission to group and it delete read and execute permission from group members

36. File Permissions - chmod
octal code:
read -> 4
write -> 2
execute -> 1
7-rwx 6-rw 5-rx 4-r 3-w,x 2-w 1-x 0-nopermission
chmod 756 sample --> rwxr_xrw_
chmod 642 sample --> rw_r___w_
chmod 755 sample --> rwxr_xr_x
chmod 700 sample --> rwx______
chmod 777 sample --> rwxrwxrwx

37. File Permissions – chown, chgrp
chown: To change owner of the file/diretory
chown ownername file/directory
chgrp: To change group of the file/directory
chgrp groupname file/directory

38. write and wall
write: It is used for to write message to another user account, but user should be logged into the server
$ write chaitu
hello
ctrld $
mesg n --> to deny messages
mesg y --> to allow messages
wall: It is used to send broadcast message to all users, whoever connected to server and mesg is "y"
$ wall
welcome world

39. mail mail: to send the mail syntax: mail username
$ mail chaitu --> this mail is transferred to chaitu user mail box (/var/spool/mail/chaitu)
subject: hello
Hi, hw r u?
ctrld $
$ mail chaitu abhi dinesh --> this mail is transferred to users chaitu, abhi and dinesh
$ mail chaitu < student --> It transfers student file contents to chaitu user

40. telnet and ftp
telnet: Telnet protocol is in_built in windows/linux. It is used for to connect to remote servers
syntax: telnet ipaddress
login: venky
password: *****
Note: from start  run  type telnet ipaddress
ftp: file transfer protocol. It is used to transfer files from one server to another server account.
syntax: ftp ipaddress
login:
password:

41. ftp ftp> ftp> ls -> server ftp> !ls -> client
ftp> pwd -> server
ftp> !pwd -> client
ftp> cd dirname -> client
ftp> lcd dirname -> server
ftp> get filename -> to download file
ftp> mget file1 file2 .. filen -> to download multiple files
ftp> put filename -> to upload file
ftp> ? -> list all ftp commands
ftp> bye -> to quit from ftp

42. Zip gzip filename -> to gip the file
gzip sample -> it create sample.gz
gunzip filename -> to unzip the file
gunzip sample.gz -> it creates sample
compress filename: To compress the file
compress filename
compress sample -> creates sample.z
uncompress sample.z -> creates sample

43. Disk Status and tee df --> It displays disk space in bytes
df -h --> It displays disk space in kilo bytes
du --> I
tee: It is used to write data to the file as well as to screen
cat test1 | tee test2t displays directory wise disk usage in form of blocks

44. Jobs foreground job: By default jobs come under foreground
$ cp file1 file2 --> foreground job
$ cp file1 file2 & --> background job
512 (PID)
$ sort sample > a1 &
513 (PID)
In foreground, user can execute only one job, but in background user can execute many jobs
How to kill foreground job? ctrl C (or) ctrl Z

45. Jobs
$ ps (or) ps -f --> displays current running process list in the current user account
$ ps -ef --> It displays currently running process list in Linux server
How to kill background job?
$ kill PID (or) $ kill -9 PID --> -9 option to kill forcibly
$ jobs --> displays only background jobs with job id's
How to bring background job to foreground?
$ fg jobid

46. Job scheduling - crontab
2. at
3. batch
1. crontab: It executes the given jobs repeatedly in server account
*(0-59) -> minutes
*(0-23) -> hours
*(1-31) -> days
*(1-12) -> month
*(0-6) -> weekday --> '0' for sunday

47. Job scheduling - crontab
$ crontab -e --> to open the crontab editor
* * * * * date --> every minute, it executes date command and it writes output into your mailbox
30 10 * * * sh script1 --> It executes script1 every day at 10:30AM
30 10 * * 0 sh script2 --> It executes script2, every sunday at 10:30AM
30 22 * * 1,3,5 sh script3 --> It executes script3 every monday, wednesday & friday at 10:30PM
,15 * * sh script4 > test.txt --> It executes script every month 1st and 15th at 10:30PM and it writes output into file test.txt
crontab -r --> to remove all crontab jobs
crontab -l --> It list all crontab jobs

48. Job scheduling - at at: It executes the given jobs only once
$ at now --> It executes the given job immediately
at> ls
at> sh script1
at> ctrl d
$ at now + 3 minutes --> after 3 minutes
$ at now + 2 hours --> after 2 hours
$ at now + 3 days --> after 3 days
$ at now + 1 month --> after 1 month

49. Job scheduling – at and batch
$ at 4PM tomorrow --> tomorrow at 4'o clock
$ at 10:30am july 10 --> july 10th at 10:30am
$ atq --> It displays all 'at' command jobs with job ids
$ atrm jobid --> It removes given job
batch: The batch jobs will execute, when server is free and server load is less
$ batch

50. Thank You