awk = Aho, Weinberger, and Kernighan
$0 = whole line $1 = first field $2 = second field [...] $NF = last field FS = field separator, default FS=\s+ OFS = output field seperator RS = record (line) separator ORS = output record seperator NR = number of records (counter from 1 to n) NF = total number of fields FILENAME = name of the current input file FNR = number of records relative to the current input file match() -> RSTART = where the pattern starts -> RLENGTH = the length of the pattern
Starters
Awk – A Tutorial and Introduction – by Bruce Barnett
Awk Introduction Tutorial – 7 Awk Print Examples
10 Awk Tips, Tricks and Pitfalls
BEGIN and END
gawk Manual – Startup and Cleanup Actions
AWK scripting: 10 BEGIN and END block examples
BEGIN { just once }
{ every record by itself }
END { just once }
Built-In Variables
8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR
String Functions
gawk Manual – String-Manipulation Functions
String concatenate
awk – concatenate two string variable and assign to a third
gawk Manual – String Concatenation
$ awk '{b=$1$2; print b}' file
$ awk '{b=$1" "$2; print b}' file
$ awk '{b=$1 FS $2; print b}' file
Regex
gawk Manual – Using Dynamic Regexps
gawk Manual – Using Regular Expression Constants
Pass shell variable as a /pattern/ to awk
How to use awk variables in regular expressions?
Passing variable to awk and using that in a regular expression