How to use awk - A powerful command ?

Awk is one of the most powerful tools in Unix used for processing the rows and columns in a file.

Awk supports most of the operators, conditional blocks, and loops available in C language.

Basic syntax of AWK

awk 'BEGIN {start_action} {action} END {stop_action}' filename

Example file

Create a file input_file with the following data. (This file can be easily created using the output of ls -l )

-rw-r--r-- 1 center center  0 Dec  8 21:39 p1

-rw-r--r-- 1 center center 17 Dec  8 21:15 t1

-rw-r--r-- 1 center center 26 Dec  8 21:38 t2

-rw-r--r-- 1 center center 25 Dec  8 21:38 t3

-rw-r--r-- 1 center center 43 Dec  8 21:39 t4

-rw-r--r-- 1 center center 48 Dec  8 21:39 t5

From the data, you can check that this file has rows and columns. The rows are separated by a new line character and the columns are separated by a space characters.

Operation 1

awk '{print $1}' input_file

Print the first column in each row.

-rw-r--r--

-rw-r--r--

-rw-r--r--

-rw-r--r--

-rw-r--r--

-rw-r--r--

Here $1, $2, $3... represents the first, second, third columns in a row respectively.

To print the 4th and 6th columns in a file use :

awk '{print $4,$6}' input_file

Operation 2

awk '{ if($9 == "t4") print $0;}' input_file

This awk command checks for the string "t4" in the 9th column and if it finds a match then it will print the entire line.

Output

-rw-r--r-- 1 pcenter pcenter 43 Dec  8 21:39 t4

 

http://www.folkstalk.com/2011/12/good-examples-of-awk-command-in-unix.html