awk

                                                                              

awk

awk is very good programming language/command  in manipulating files which have patterns separated by space or other delimiters. It does these  operations  faster than other basic  unix commands like sed and grep.

awk’s power lies in its “one line” editing option which makes it more a command than a programming language.

Examples:

Example1)

suppose that you have a file which contains 4 columns of an SQL  spool file.

/home/b3456/$ cat  member_list.txt                         (Note: here /home/b3456/$  is the prompt string)

Ajit kumar                1000             BLR

sachin Sharma        2500             MUM

Ajay gupta                6560             MUM

Srinivasan   R          4509              NDL

Ahmed  javed          7845              CHE

To print only the city codes(third field or column ) enter the following  command.

/home/b3456/$ awk  ‘{print $3}’   member_list.txt

BLR

MUM

MUM

NDL

CHE

Example 2)

 you want to get the member whose amount withdrawn ( 2^nd  column)  is greater than  or equal to 6000 and less than 7000 ,enter the command

/home/b3456/$ awk  ‘  {if ( $2  >=  6000 && $2  < 7000) print $1 }’    member_list.txt

Ajay gupta                

Example 3)

 To get the total size of a group of files  in  a directory.

/home/b3456/$  ls  –lrt

 rw-r--r--    1 b3456  Administ    19738       Feb  1  2011  NOV_2010_3.pdf

-rw-r--r--    1 b3456  Administ    18176      Feb  1  2011  DEC_2010.pdf

--rw-r--r--    1 b3456  Administ   739840   Jul  8 23:09    2011_ITR1_r2.xls

-rw-r--r--    1 b3456  Administ    11455     Jul  8 23:13     ITR1_AJTPN1033E.xml

-rw-r--r--    1 b3456  Administ    94058     Jul  9 14:08     09072011020807_13102006

-rw-r--r--    1 b3456  Administ      101        Jul  9 14:10     address_TAX.txt

-rw-r--r--    1 b3456  Administ    43237     Jul  9 14:17     XXXPN1033X_ITR-V.zip

-rw-r--r--    1 b3456  Administ  1046954  Nov 21 14:29 EDU_LOAN_STMT.pdf

Enter the following command.

/home/b3456/$  ls  -lrt | awk ' BEGIN  {c = 0}{ c  += $5 } END{print  c}' 

973559

Note that you don’t have to use ‘$’ symbol for printing a variable .

Example 4)

Many a times ,you may want to pass a shell variable to awk  in the command line or inside

Shell-script and do some conditional manipulations based on the variable .

Consider  a situation where you need to compare  a name variable of the shell with the names in the file member_list.txt.

The script

#!/usr/bin/sh

……………..#lines of commands

……………..

p_name=`echo $m_name`         #p_name Is a shell variable.

awk   -v    myp_name=$ p_name   ‘{ if  ( $1 == myp_name)  print  $0 }’   member_list.txt.

…………….

Here the awk command prints the entire line which contains the name field same as that of value of variable p_name

  Example 5)

A  single space or a  sequence  of  space  characters is the  default delimiter   for fields, if there are any other use  awk   with option –F and mention the delimiter.

If the file member_list2.txt contained  the following,

/home/b3456/$ cat  member_list2.txt

Ajit kumar|1000|BLR

sachin Sharma|2500|MUM

Ajay gupta|6560|MUM

Srinivasan R|4509|NDL

Ahmed javed|7845|CHE

Then  to print only the city codes(third field or column ) as in example 1, awk can be used as follows.

/home/b3456/$ awk  -F  “|”  ‘{ print $3 }’    member_list2.txt

BLR

MUM

MUM

NDL

CHE