Built-in Variables (UNIX in a Nutshell: System V Edition)

11.4. Built-in Variables

Version	Variable	Description
`awk`	`FILENAME`	Current filename
	`FS`	Field separator (a space)
	`NF`	Number of fields in current record
	`NR`	Number of the current record
	`OFMT`	Output format for numbers (`"%.6g"`) and for conversion to string
	`OFS`	Output field separator (a space)
	`ORS`	Output record separator (a newline)
	`RS`	Record separator (a newline)
	`$0`	Entire input record
	`$``n`	nth field in current record; fields are separated by `FS`
`nawk`	`ARGC`	Number of arguments on command line
	`ARGV`	An array containing the command-line arguments, indexed from 0 to `ARGC - 1`
	`CONVFMT`	String conversion format for numbers (`"%.6g"`) (POSIX)
	`ENVIRON`	An associative array of environment variables
	`FNR`	Like `NR`, but relative to the current file
	`RLENGTH`	Length of the string matched by `match()` function
	`RSTART`	First position in the string matched by `match()` function
	`SUBSEP`	Separator character for array subscripts (`"\034"`)
`gawk`	`ARGIND`	Index in `ARGV` of current input file
	`ERRNO`	A string indicating the error when a redirection fails for `getline` or if `close()` fails
	`FIELDWIDTHS`	A space-separated list of field widths to use for splitting up the record, instead of `FS`
	`IGNORECASE`	When true, all regular expression matches, string comparisons, and calls to `index()` s ignore case
	`RT`	The text matched by `RS`, which can be a regular expression in `gawk`