LINUX

The below are the Linux commands which are used frequently in Teradata Projects(real-time)

(Followed by regular class of VINAYTECH)

Directory operations

mkdir vinaytech  --creating directory

ch vinaytech     --changing directory (connecting to the directory)

pwd               --

rmdir vinaytech   --removing directory

cd..              --going to previous directory

cd..\..           -- two directories back

cd                --going to root directory

clear             -- clearing the scrren

CAT 

Creating files


A) By using TOUCH command (for ZERO BYTE FILE creation) 
B) By using CAT command
C) By using VI EDITOR

Cat Command:

 To create/append/modify content in the file.

Examples:

Crating:

Cat > tdclass

EID ENAME ELOC
1 X HYD
2 Y MUM
3 Z USA

Ctrl + d

To view the file

Cat tdclass

Copying file

cp tdclass tdclass1

Remove file

rm tdclass1

Moving file

Mv tdclass1 tdclass2

Concatenate and displaying data

Cat tdclass1 tdclass2

Concatenate and redirect to other file

Cat tdclass1 tdclass2 > tdclass3

WC 

   Wc   -->Word count

   Real time:
            For Reconciliation and Unit testing
    While performing ETL operations on files

Wc -l <Filename>  -->Count no of lines
Wc -c <Filename>  -->Number of characters in a file
Wc -w <Filename>  -->Number of words

   To see words and Lines at a time
wc -wl


   Piping Operator (||)--> Redirects the information.

wc lc tdclass || tee filestats

In this situation lines and characters info redirected to
filestats file.

TEE 

  Tee : Display and Redirect

  Real Time: 
           Most frequently used command at the time of 
           executing utilities in Unix prompt / script
           
           wc lc tdclass || tee filestats
   
           In the above example result displayed and redirected.

SED

  SED : (Stream Editor)

It is a special editor for working/ modifying / substituting
etc..operations on the files data.

Mostly we use SED and Option s for Substitution.

Examples: 
          sed 's/HYD/Hyderabad/' tdclass

  sed 's/HYD/Hyderabad/3g' tdclass -->3rd line to all
 occurances

  sed 's/HYD/Hyderabad/g' tdclass -->All occurances replaced

  sed -n '$=' tdclass-->Counts lines in a file

  sed 's/HYD/Hyderabad/g' tdclass > Tdresult
--> Result redirection


  etc...

AWK

   AWK -->
    Most powerful command for processing rows and columns in a file

Awk supports
A) Conditional Operators
B) Blocks
C) Loops
D) String functions
E) Associative Arrays

  Some people using awk command for automating(SCHDULING)the    applications in Unix environment inside the scripts.

  AWK 'BEGIN {start_action} {action} END {end_action}' <filename>

 Examples: 

 awk '{print 1$}' tdclass -->first column it returns


 awk '{print 1$,3$}' tdclass -->first 3 columns it returns(1-3                                                               columns)

GREP

GREP-->GLOBALLY SEARCH A REGULAR EXPRESSION AND PATTERN

Useful for identifying a partial / full string in the file.

Syn: Grep <text> <filename>

Ex: Grep vinay tdclass

Grep "td class" tdclass --> Two words validation

Grep vinay tdclass tdclass1 -->multi file                                                          verification

Grep vinay * --> All files verification

CHMOD

  CHMOD : Changing Mode 

Useful for assigning and removing privileges / permissions

Users      Group     Owners

r w x       r w x    r w x

Octal notation : r --> 4  w-->2 x-->1

Examples:

chmod u+w tdclass --> Users write access

chmod o+x tdclass--> Owners execute access

chmod 000 tdclass--> No access to owners ,groups and users

chmod 724 tdclass->Users Full access,Group write,Owners                                                            read 

chmod 777 tdclass-->Full privileges to Users,Owners and                                                                 Group

HEAD

        HEAD-->DISPLAY FIRST LINES OF THE FILE

SYN : Head -n <Filename>

EX: Head -2 tdclass

TAIL

       TAIL-->DISPLAY LAST LINE OF A FILE

SYN: Tail -n <Filename>

EX:  Tail -2 tdclass

REAL TIME: To see header and Footer information embedded

                   in the data

   To eliminate header and footer while loading 

                    the data etc..

CREATING HIDDEN FILE

Cat > .tdclass

PS

       PS COMMAND:(PROCESS STATUS COMMAND)

REAL TIME : 

a) To identify processes running

b) To kill / abort /terminate /halt process

etc...

Process is nothing but an instance of the Executing Program

There are two important terminologies:

a) PID (Process ID) b) PPID (Parent Process ID)

KILL

        KILL command: Kills the process

Syn: Kill [-Signal] processid

Ex: a) Kill 237

   b) Kill =15 237

Signal : Helps the system to implement the option to the 

process id

0-> Null Signal

2-->Hangup

3-->Quit

15-->Terminate

VI EDITOR

      VI EDITOR:(VIRTUAL INTERPRITER / INTERFACE)

Syn: 

VI <filename> <Enter Key>

By pressing Escape with the below characters enter the data

A or a

I or i

O or o 

To goto the next / previous characters use the below

L H J K

TO GOTO 3 LINES BACK WE USE 3K / 3H / 3I

W->ONE WORD FORWARD

2W->TWO WORDS FORWARD

P->ONE WORD PREVIOUS

2P->TWO WORDS PREVIOUS

$-->END KEY

^ OR Q --> Home Key

H--> Beginning of the Page

M->Middle of the Page

L->End of the page

x->deleting character

CTRL + D -->DELETING LINE

CTRL + W --> DELETING WORD

CTRL DD->CUT

CTRL P-->PASTE

: W <FILENAME>  // W FOR SAVING

: q! //Quitting

: wq! //Save and Quit

: set nu // assigns line numbers

:set nonu //removing line numbers

:3  //going to third line

NOTE: FOR MORE DETAILED COMMANDS REFER TO THE SOFTCOPY DOCUMENT

            GIVEN AT VINAYTECH HOUSE INSTITUTE.