Table of Contents

AWK - AWK Patterns

Assuming a file exists with the following contents: 

10   Peter     Terence   Roux        45
11   Virginia  Genevieve  Roux        45
12   Felix     Devon     Roux         5
13   David     Bruce     Stevenson   48
14   Bob       James     Smith       16
48   Adam      Winter    Ridley      23

Matching Patterns

To only print out lines which match a specific search criteria: 

awk '/45/ {print $2,$4}' test.txt

returns: 

Peter Roux
Virginia Roux

NOTE: This only prints out the lines from the file which contained the number 45.

Multi-line Output with Patterns

To output onto multiple lines: 

awk '/45/ {print $2,$3,$4 ; print $1, $5}' test.txt

returns: 

Peter Terence Roux
10 45
Virginia Genevieve Roux
11 45

NOTE: This only prints out the lines from the file which contained the number 45.

  • But also prints out a 2nd line because of the use of the semicolon.

NOTE: A semicolon does not have to be used to allow using multiple commands.

For instance issue the following command instead: 

awk '/45/ {print $2,$3,$4} {print $1, $5}' test.txt

returns: 

Peter Terence Roux
10 45
Virginia Genevieve Roux
11 45
12 5
13 48
14 16
48 23

This time an altogether different result is produced, than when a semicolon was used.

The reason for this is that the pattern that is used, /45/ is only applied to the command immediately following it. In this example, this was only against fields $2, $3 and $4.

The 2nd print statement is not affected by the pattern and would apply to all fields in the input file.

Match using Multiple Patterns

To search for more than one pattern match at a time, issue the following command: 

awk '/45|48/ {print $2,$4}' test.txt

returns: 

Peter Roux
Virginia Roux
David Stevenson
Adam Ridley

NOTE: The pipe symbol | is used to provide multiple patterns.

Match against specific field

To restrict the match to only a specific field: 

awk '$5 ~ /45|48/ {print $2,$4}' test.txt

returns: 

Peter Roux
Virginia Roux
David Stevenson

NOTE: Adam Ridley is not displayed even though the source file has a 48 as part of his record.

  • The tilda ~ ties the match to a specific field.

Match not against a specific field

To have the match be the opposite of matching a specific field: 

awk '$5 !~ /45|48/ {print $2,$4}' test.txt

returns: 

Felix Roux
Bob Smith
Adam Ridley

NOTE: The exclamation mark and tilda (!~) together informs to not match to a specific field.

Match in a Range

To have the match be the opposite of matching a specific field: 

awk '/4[2-8]/ {print $2,$4}' test.txt

returns: 

Peter Roux
Virginia Roux
David Stevenson
Adam Ridley

NOTE: This finds all fields with values between 42 and 48.