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AWK STRING SUBSTITUTION1					Replaces first match of regexp with replstring						
					sub(regexp,replstring,mystring)						
AWK STRING SUBSTITUTION2					Replaces ALL matches of regexp with replstring						
					gsub(/o/,"O",mystring)						

AWK SPLIT FUNCTION					Chop up string and place values into integer indexed array						
					numelements=split("Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec",mymonths,",")						

$  awk 'BEGIN{ORS="=";} {print;}' student-marks					
					
					
					
					
					
					
					
The output record separator is the equivalent of the record separator, but					
describes the delimiter only in the output of the awk script.					

$cat student.awk					
BEGIN {					
        RS="\n\n";					
        FS="\n";					
}					
{					
        print $1,$2;					
}					
The record separator describes how the awk output hs its records					
separated, the default is newline but anything can be set.					

PASSING SHELL VARIABLES INTO AWK					#!/bin/bash						
					echo -n "Enter hour (0-23): "						
					read hour						
					date | awk -v awk_hr=$hour 'BEGIN { FS="[ :]+"; } ; $4 >= awk_hr { print $2, $3, $8 }'						
											

$ awk '{print "Processing Record - ",NR;}END {print NR, "Students Records are processed";}' student-marks						
						
Output : 		Processing Record -  1				
		Processing Record -  2				
		Processing Record -  3				
		Processing Record -  4				
		Processing Record -  5				
		5 Students Records are processed				

AWK + MULTILINE RECORDS					# Records are separated by blank lines.						
					# Each line is one field.						
					BEGIN { RS = "" ; FS = "\n" }						
					{						
						print "Name is:", $1					
					}						

AWK MATCH FUNCTION					
Returns the relative position of the regexp, starting digit and length						
					print match(mystring,/you/), RSTART, RLENGTH						

do {					
	print "I get printed				
} while ( count != 1 )					
					
for ( initial assignment; comparison; increment ) {					
	code block				
}					
					



while(1) {
        print "iteration",x
        if ( x == 10 ) {
                break
        }
        x++
}
* We can always use continue instaed

#Function : Returns the length of a found string						
print length(mystring)			OR	print length($var)		

Function : Returns the relative position (index) of the search word						
print index(mystring)						

$ awk '{print FILENAME, FNR;}' student-marks bookdetails
student-marks 1
student-marks 2
student-marks 3
student-marks 4
student-marks 5
bookdetails 1
bookdetails 2
bookdetails 3
bookdetails 4
bookdetails 5

$ awk '{print FILENAME}' student-marks
student-marks
student-marks
student-marks
student-marks
student-marks

$ awk -F 'FS' 'commands' inputfilename				Sample code :	
OR					
$ awk 'BEGIN{FS="FS";}'					
					
					
The field separator default value is space ' '					
The field separator can be set to any other delimiter					
by using the above options					
					
					



############


$ cat etc_passwd.awk
BEGIN{
FS=":";
print "Name\tUserID\tGroupID\tHomeDirectory";
}
{
        print $1"\t"$3"\t"$4"\t"$6;
}
END {
        print NR,"Records Processed";

CALL AWK FROM SCRIPT					


awk -f myscript.awk myfile.in						
					chmod +x myscript.awk   and ./myscript.awk myfile.in						

AWK SETTING DELIMITERS					

awk -F":" '{ print $1 }' /etc/passwd						
					BEGIN {						
						FS=":"					
					} 						
					{ print $1 } 						

awk -f myscript.awk myfile.in						
chmod +x myscript.awk   and ./myscript.awk myfile.in						

AWK AND CONDITIONAL EXPRESSIONS					{ 				! /matchme/ { print $1 $3 $4 }    is equivalent to		
					  if ( $5 ~ /root/ ) { 				{ 		
					          print $3 				  if ( $0 !~ /matchme/ ) { 		
					  }				          print $1 $3 $4 		
					Boolean Operators :				  } 		
					( $1 == "foo" ) && ( $2 == "bar" ) { print }				}		
											
											

1. awksubstring 
2. awklength
3. awkindex
4. awktolower
5. awktoupper
6. awkmatch
7. awkstrsub
8. awksplit
9. awkdelimit
10. awkpassingvars
11. callawkfromscript
12. awkexecutable
13. awkmultiline
13. awkconditionals
13. awkloops
14. awkfieldseparators
15. awkrecordseparators
16. awkrecordseparators(out)
17. awkfieldseparators(out)
18. awknumberofrecordsvar
19. awknumberoffieldsvar

Converts all lowercase to upper						
print toupper(mystring)						

Converts all upper case to lower case						
print tolower(mystring)						

awk '{print substr($1,3)   }' temp						
substr(mystring,startpos,maxlen)						
'a[substr($0,135,1)]++{exit 1}' test.txt						
if(substr($0,750,1)=="1"						
if(substr($rec1,750,1)=="X" || substr($rec2,750,1)=="X"						
print substr(mystring,9,3)						

$ awk '{print NR,"->",NF}' student-marks
1 -> 5
2 -> 5
3 -> 4
4 -> 5
5 -> 4

Input :	BEGIN {			Output : 	Hello there Jim!	
		FS="\n"		Sample Code :		
		RS=""				
		OFS=", "		$ awk -F':' 'BEGIN{OFS="=";} {print $3,$4;}' /etc/passwd		
		}				
		{				
		print $1, $2, $3				
		}				
The OFS describes the kind of delimiter than will be used						
in the output of the awk script.