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• The Awk Reference
  • General Syntax
  • AWK Filtering-Usage Example
    • All equivalent
  • Variables
  • Logical Operators
  • Relational Operators
  • Number Processing
  • AWK Program on a File
  • BEGIN and END Sections
  • Arrays
  • Built-in Variables
  • Built-in Functions
• Example Program for Practice

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AWK Help

AWK Manpages

The Awk Reference

NOTES

AWK operates at the field level. It can easily access, transform, and format individual fields in a record. It also accepts regular expressions for pattern matching

It has C-type programming constructs, variables, and several built-it functions.

General Syntax

AWK follows the general syntax of-

$ awk options `address {actions}` file

the syntax constituents are the same as in sed and also consists of two sections-an address and an action

the major difference is that the action is enclosed within curly braces

the address and action constitute what is known as an AWK program

these programs are mostly one line long, although they can span several lines as well

AWK Filtering-Usage Example

$ awk `/director/ {print}` emplist

address section director selects the lines that are processed in the action section

if the address is missing, then the actions applies to all the lines in the file

if the action is missing, then the entire line will be printed

either the address or action is optional but both must be enclosed within a pair of single quotes

the print statement, when used without any field specifiers prints the entire line

printing is the default action of awk

All equivalent

$ awk `/director/` emplist
$ awk `/director/{print}` emplist
$ awk `/director/{print $0}` emplist

Variables

all variables have a global scope in AWK

$ awk -F "|" `$3=="director" && $6>700000
        count=count+1
        printf "%3d %-20s %-12s \n", count, $,...
` emplist

- <–left justify

Logical Operators

Relational Operators

Number Processing

{print $1*$1}

AWK Program on a File

BEGIN and END Sections

Arrays

awk handles one-dimensional arrays. No array declarations are necessary

an array is considered to be declared the moment it is used, it is automatically initialized to zero

Built-in Variables

NR number of records read

FS input field separator

OFS output field separator

NF no. of fields in current record

FILENAME current input filename

ARGC no. of arguments

ARGV list of arguments

Built-in Functions

int(x) return integer value of x

sqrt(x)

length length of complete record

length(x)

substr(s1,s2,s3) return string of length s3 with start position s2 in s1

index(s1,s2) return the position of string s2 in s1

split(s,a) split string s into array a

system("cmd") run a linux command

Example Program for Practice

program.awk

BEGIN {
    FS = "|"
    print "\t\tResults:\n"
    printf("%-20s %-6s\n","Full Name",  "Percentage")
    printf("%-20s %-6s\n", "-----------","-----------")
}

{
    total=int($2)+int($3)+int($4)+int($5)+int($6);
    pc=(total)/5;

    if (pc >= 66) grade ="Distinction";
    else if (pc >= 60) grade ="First Class";
    else grade="PASS";
    if ( pc<40) grade ="FAIL";
    printf("%-20s %-6s\n",$1,grade);
}

END{
}

inputfile

Ish  Studaynt | 60 | 56 | 80 | 67 | 64
Hoovas  Imparis | 85 | 67 | 88 | 78 | 85
Goated  Saus | 60 | 56 | 44 | 76 | 68
Tibh  Krecha | 15 | 7 | 14 | 20 | 30
Topar  Smasar | 48 | 46 | 60 | 49 | 53
Quandale Dingle | 100 | 100 | 100 | 100 | 100