Unix Utility - AWK

AWK - Aho Weinberger Kernighan

AWK is an interpreted programming language designed for text processing and typically used as a data extraction and reporting tool. 

It is a standard feature of most Unix-like operating systems. AWK was very popular in the late 1970s and 1980s, but from the 1990s has largely been replaced by Perl, on which AWK had a strong influence.

Some of the key features of Awk are: 

• Awk views a text file as records and fields.
• Like common programming language, Awk has variables, conditionals and loops.
• Awk has arithmetic and string operators.
• Awk can generate formatted reports

Awk reads from a file or from its standard input, and outputs to its standard output. Awk does not get along with non-text files.

Syntax:

awk '/search pattern1/ {Actions}
     /search pattern2/ {Actions}' file

In the above awk syntax:

• search pattern is a regular expression.
• Actions – statement(s) to be performed.
• several patterns and actions are possible in Awk.
• file – Input file.
• Single quotes around program is to avoid shell not to interpret any of its special characters. 

Example:

$ cat employees.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Sanjay  Sysadmin   Technology  $7,000
400  Nisha   Manager    Marketing   $9,500
500  Randy   DBA        Technology  $6,000

$ awk '/n/ {print $2,$NF;}' employees.txt

Thomas $5,000
Jason $5,500
Sanjay $7,000
Nisha $9,500
Randy $6,000

Good to visit:

http://en.wikipedia.org/wiki/AWK

http://www.grymoire.com/Unix/Awk.html

http://www.thegeekstuff.com/tag/awk-tutorial-examples/