AWK

AWK- an advanced fileter

aho,weinberger and kernighan

gawk in linux

awk options 'selection criteria {action}' files

printing is the default action of awk

awk '/rahul/' 1.txt
awk '/rahul/{print}' 1.txt

both are same and will print the lines containing rahul

awk -F" " '/rahul/{print $2,$3}' 1.txt
it will print 2nd and 3rd parameter in all lines containing rahul delimited by a space

 awk -F " " 'NR==1,NR==10{print $1,$2,$3}' 1.txt
it will print first 10 lines ;its 1st , 2nd and third parameters delimited by space.

awk 'BEGIN{FS=" "}
=> NF!=6{
=> print "record number",NR,"has",NF,"fields"}' 1.txt

using built in variables

NR no of records
FS field separator
OFS output fiels separator
NF Number of fields in current line
FILENAME current input file
ARGC no of arguments in current line
ARGV List of arguments


using functions

awk -F" " 'length($2) < 1' 1.txt

those which have short second parameter