Some variable names have a special meaning to the awk interpreter.
The following are '''special variables''' within awk:
| '''Variable''' | Description |
| [[ARGC?]] | An informative variable that provides command line parameter information |
| [[ARGV?]] | An informative [[array?]] that provides command line parameter information |
| [[CONVFMT?]] | A control variable that specifies the conversion format of numerical strings |
| ENVIRON | An informative array that contains the environment strings |
| [[FILENAME?]] | An informative variable that provides the current input [[filename?]] |
| FNR | An informative variable that provides the number of records read from current file |
| FS | A control variable that specifies the input field separator |
| NF | An informative variable that provides the number of fields within the current record |
| [[NR?]] | An informative variable that provides the total number of records read so far |
| [[OFMT?]] | A control variable that specifies the output format of numerical values |
| [[OFS?]] | A control variable that specifies the output field separator |
| [[ORS?]] | A control variable that specifies the output record separator |
| [[RLENGTH?]] | An informative variable that provides the length of the currently matched substring |
| RS | A control variable that specifies the input record separator |
| [[RSTART?]] | An informative variable that provides the start index of the currently matched substring |
| [[SUBSEP?]] | A control variable that specifies the subscript separator for multidimensional arrays |