Linux - AWK Command

Jun 1, 2018 · 4 min read · Linux Commands

AWK is a line-oriented language basically used to manipulating data and generate reports. awk script no required any compiler to compile. In awk we use variables, numeric functions, string function and logical operators.

Awk is abbreviated from the names of the developers – Aho, Weinberger, and Kernighan.

An awk program operates on each line of an input file. Basic components are

BEGIN { …. initialization awk commands …}
{ …. awk commands for each line of the file…}
END { …. finalization awk commands …}

1ls -l | awk 'BEGIN {sum=0} {sum=sum+$5} END {print sum}'

Awk Variables

Variables	Description
$1,$2… $n	fields variables [$0 for entire line]
NR	Number Row - keeps the current count of the row
NF	Number field - keeps the current count if the fields
FS	field separator [The default is “white space” ]
RS	Record separator [The default is “New line character”]
OFS	Specifies the Output separator.
ORS	Specifies the Output separator.
ARGC	Retrieves the number of passed parameters.
ARGV	Retrieves the command line parameters. ARGV[1],ARGV[2]….
ENVIRON	Array of the shell environment variables and corresponding values.
IGNORECASE	To ignore the character case.

AWK Control Statements

if (condition) statement [ else statement ]
while (condition) statement
do statement while (condition)
for (expr1; expr2; expr3) statement
for (var in array) statement
break
continue

Examples

Employee file employee.txt which having employee records

1ajay manager account 45000
2sunil clerk account 25000
3varun manager sales 50000
4amit manager account 47000
5tarun peon sales 15000
6deepak clerk sales 23000
7sunil peon sales 13000
8satvik director purchase 80000

Print line by line from file

 1awk '{print}' employee.txt
 2
 3#Output
 4ajay manager account 45000
 5sunil clerk account 25000
 6varun manager sales 50000
 7amit manager account 47000
 8tarun peon sales 15000
 9deepak clerk sales 23000
10sunil peon sales 13000
11satvik director purchase 80000

Print the lines which match the given pattern

1awk '/manager/ {print}' employee.txt 
2
3# Output:  
4ajay manager account 45000
5varun manager sales 50000
6amit manager account 47000

Splitting a Line Into Fields

 1awk '{print $1,$4}' employee.txt 
 2
 3#Output:  
 4ajay 45000
 5sunil 25000
 6varun 50000
 7amit 47000
 8tarun 15000
 9deepak 23000
10sunil 13000
11satvik 80000

More Examples

 1#  To find/check for any string in any specific column
 2awk '{ if($3 == "B6") print $0;}' geeksforgeeks.txt
 3
 4# To print the squares of first numbers from 1 to 6
 5awk 'BEGIN { for(i=1;i<=6;i++) print "square of", i, "is",i*i; }' 
 6
 7# Output
 8square of 1 is 1
 9square of 2 is 4
10square of 3 is 9
11square of 4 is 16
12square of 5 is 25
13square of 6 is 36
14
15# Use of NR built-in variables (Display Line Number)
16awk '{print NR,$0}' employee.txt 
17
18# Output
191 ajay manager account 45000
202 sunil clerk account 25000
213 varun manager sales 50000
224 amit manager account 47000
235 tarun peon sales 15000
246 deepak clerk sales 23000
257 sunil peon sales 13000
268 satvik director purchase 80000 
27
28# Use of NF built-in variables (Display Last Field) 
29awk '{print $1,$NF}' employee.txt 
30
31# Output
32ajay 45000
33sunil 25000
34varun 50000
35amit 47000
36tarun 15000
37deepak 23000
38sunil 13000
39satvik 80000 
40
41
42# Another use of NR built-in variables (Display Line From 3 to 6)  
43awk 'NR==3, NR==6 {print NR,$0}' employee.txt 
44
45# Output
463 varun manager sales 50000
474 amit manager account 47000
485 tarun peon sales 15000
496 deepak clerk sales 23000 
50
51# To count the lines in a file:  
52awk 'END { print NR }' employee.txt 
53
54# To find/check for any string in any specific column
55awk '{ if($3 == "B6") print $0;}' employee.txt 
56
57# To print the squares of first numbers from 1 to n say 6 
58awk 'BEGIN { for(i=1;i<=6;i++) print "square of", i, "is",i*i; }' 
59
60# Output
61square of 1 is 1
62square of 2 is 4
63square of 3 is 9
64square of 4 is 16
65square of 5 is 25
66square of 6 is 36