AWK Built-in Variables

A common choice for manipulating and processing large text files on UNIX systems is awk. I was using awk in March of 2017 and thought it would be helpful to have a list of awk built-in variables for future reference.

Name	Description
`FS`	The field separator (or column separator). This defines the character that separates each column of data, such as `\t` for tab-separated value files. It can be assigned directly, or awk can be invoked with the file flag `-F` in order to parse the separator out of the file automatically.
`OFS`	The field separator to use when outputting. By default, the output field separator is the space character.
`RS`	The record separator (or row separator). This defines the character that separates each row of data, such as `\n` for newline-delimited files.
`ORS`	The output record separator. The delimiter is output between every record instance.
`NR`	The number of records processed (line number) across all files
`FNR`	The number of records processed (line number) in just the current file.
`NF`	The number of fields in the current record (number of columns in the current row).