Table 1. Built-in awk Variables

NR: sequence number of the current input record. The entire value of the current input record.

NF: the number of fields in the current record.

$1-$N: ordered fields in the current record.

FS: input field delimiter (white space—tab or space—by default).

OFS: output field separator (space character by default).

RS: input record delimiter (newline by default).

ORS: output record delimiter (newline by default).

FILENAME: current input file name. When reading from standard input, FILENAME is set to - (dash).