Some variable names have a special meaning to the awk interpreter.
List of special variables
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