Useful AWK Commands

prints column 1	awk '{print $1}'
filters lines with "abc" (same as grep abc)	awk '/'abc'/'
filters lines with "abc" and prints column 1	awk '/'abc'/ {print $1}'
prints column 2 and 3	awk '{print $2,$3}'
prints all columns	awk '{print $0}'
gets instructions from a file	awk -f script.awk in putfile
executes a program using data from input file	awk 'program' inputfile
classic hello world	awk "BEGIN {print \"Hello World\"}"
Print what's entered on the command line until EOF (^D)	awk '{print}'
awk script for the classic "Hello, world!" (make it executable with chmod and run it as-is)	#! /bin/awk -f BEGIN { print "Hello, world!" }
Comments in awk scripts	# This is a program that prints \ "Hello, world!" # and exits
prints first column on a : delimited file	awk -F: '{print $1}' /etc/passwd
prints length of each line	cat /etc/passwd | awk '{print length($0)}'
prints the length of the longest line	cat /etc/passwd | awk '{if (length($0)>max) max=length($0)} END {print max}'
shows all lines longer than 80	cat passwd.sample | awk 'length($0)>80'
same as above but instead of printing the lines, this prints the lengths of those lines	cat passwd.sample | awk 'length($0)>80 {print length($0)}'
prints line w/ more than 2 fields (NF stands for Number of Fields)	awk 'NF>2' file.txt
Print seven random numbers from 0 to 100	awk 'BEGIN { for (i = 1; i <= 7; i++) print int(101 * rand()) }'
prints the sum of file sizes (in bytes) in the current directory	ls -l | awk '{sum=sum+$5} END {print sum}'
Print the total number of kilobytes used by files in the current directory	ls -l . | awk '{ x += $5 } ; END { print "total kilobytes: " (x + 1023)/1024 }'
print number of lines (NR stands for Number of Rows)	awk 'END {print NR}' passwd.sample
prints lines whose field 3 is equal to "root"	ls -l | awk '$3=="root"'
prints bcd	echo aaaabcd | awk '{ sub(/a+/, ""); print }'
prints even-numbered lines	awk 'NR%2==0' file.txt
weird stuff	ls -lh | awk '{ owner = $3 ; $3 = $3 " 0wnz"; print $3 }' | uniq
prints number of lines	awk 'END {print NR}' passwd.sample
extract username and uid from inputfile	awk -F: '{print "Username: " $1"\t\tUID: "$3}' passwd.sample
prints only those lines containing "abc"	awk '/abc/ {print}' myfile.txt
uses a more complicated regular expression	awk '/[0-9]+\.[0-9]*/ {print}' inputfile
prints lines whose 2nd field is equal to "2"	ls -l | awk '$2==2 {print}'   * In this example, $2==2 is the condition. If that is not     satisfied, it will not execute the action which is {print}
uses another regular expression	ls -l | awk '$3 ~ /abc/ {print}'
prints all lines that doesn't have "abc"	ls -l | awk '! /abc/ {print}'
uses && operator for a more precise selection	awk '$3=="abc" && $5==4096 {print}' ls.sample