Linux/UNIX Awk Command Tutorial with Examples

AWK  Stands for ‘Aho, Weinberger, and Kernighan‘

Awk is a scripting language which is used  for  processing or analyzing text files. Or we can say that awk is mainly used for grouping of data based on either a column or field , or on a set of columns. Mainly it’s used for reporting data in a usefull manner. It also employs Begin and End Blocks to process the data.

Syntax of awk :

# awk ‘pattern {action}’ input-file > output-file

Lets take a input file with the following data

$ cat  awk_file
Name,Marks,Max Marks
Ram,200,1000
Shyam,500,1000
Ghyansham,1000
Abharam,800,1000
Hari,600,1000
Ram,400,1000

Example:1 Print all the lines from a file.

By default, awk prints all lines of a file , so to print every line of above created file use below command :

[email protected]:~$ awk ‘{print;}’ awk_file
Name,Marks,Max Marks
Ram,200,1000
Shyam,500,1000
Ghyansham,1000
Abharam,800,1000
Hari,600,1000
Ram,400,1000

Example:2 Print only Specific field like 2nd & 3rd.

[email protected]:~$ awk -F “,” ‘{print $2, $3;}’ awk_file
Marks Max Marks
200 1000
500 1000
1000
800 1000
600 1000
400 1000

In the above command we have used the option  -F “,”  which specifies that comma (,) is the field separator in the file

Example:3 Print the lines which matches the pattern

I want to print the lines which contains the word “Hari & Ram”

[email protected]:~$ awk ‘/Hari|Ram/’ awk_file
Ram,200,1000
Hari,600,1000
Ram,400,1000

Example:4 How do we find unique values in the first column of name

[email protected]:~$ awk -F, ‘{a[$1];}END{for (i in a)print i;}’ awk_file
Abharam
Hari
Name
Ghyansham
Ram
Shyam

Example:5  How to find the sum of data entry in a particular column .

Synatx :  awk -F, ‘$1==”Item1″{x+=$2;}END{print x}’ awk_file

[email protected]:~$ awk -F, ‘$1==”Ram”{x+=$2;}END{print x}’ awk_file
600

Example:6  How to find the  total of all numbers in a column.

For eg we take the 2nd and the 3rd column.

[email protected]:~$ awk -F”,” ‘{x+=$2}END{print x}’ awk_file
3500
[email protected]:~$ awk -F”,” ‘{x+=$3}END{print x}’ awk_file
5000

Example:7  How to find the sum of individual group records.

Eg if we consider the first column than we can do the summation for the first column based on the items

[email protected]:~$ awk -F, ‘{a[$1]+=$2;}END{for(i in a)print i”, “a[i];}’ awk_file
Abharam, 800
Hari, 600
Name, 0
Ghyansham, 1000
Ram, 600
Shyam, 500

Example:8 How to find the sum of all entries in second column  and append it to the end of the file.

[email protected]:~$ awk -F”,” ‘{x+=$2;y+=$3;print}END{print “Total,”x,y}’ awk_file
Name,Marks,Max Marks
Ram,200,1000
Shyam,500,1000
Ghyansham,1000
Abharam,800,1000
Hari,600,1000
Ram,400,1000
Total,3500 5000

Example:9 How to find the count of entries against every column based on the first column:

[email protected]:~$ awk -F, ‘{a[$1]++;}END{for (i in a)print i, a[i];}’ awk_file
Abharam 1
Hari 1
Name 1
Ghyansham 1
Ram 2
Shyam 1

Example:10 How to print only the first record of every group:

[email protected]:~$ awk -F, ‘!a[$1]++’ awk_file
Name,Marks,Max Marks
Ram,200,1000
Shyam,500,1000
Ghyansham,1000
Abharam,800,1000
Hari,600,1000

AWK Begin Block

Syntax for BEGIN block is

# awk ‘BEGIN{awk initializing code}{actual AWK code}’ filename.txt

Let us create a datafile with below contents

Example:11  How to populate each column names along with their corresponding data.

[email protected]:~$ awk ‘BEGIN{print “Names\ttotal\tPPT\tDoc\txls”}{printf “%-s\t%d\t%d\t%d\t%d\n”, $1,$2,$3,$4,$5}’ datafile

Example:12 How to change the Field Separator

As we can see space is the field separator in the datafile , in the below example we will change field separator  from space to “|”

[email protected]:~$ awk ‘BEGIN{OFS=”|”}{print $1,$2,$3,$4,$5}’ datafile